Why is there a PLL in CPU?

Question: I read that PLL are used in CPU to generate the clock, but I can't understand why.
I don't really have any guess of why this is.
Comment: It is probably too broad but I got very relevant answers that will hopefully help other people.
Comment: I would shut this question down as "too broad". It is like asking "why are there CMOS gates instead of transistors in a CPU"...
Comment: Why close this? It invites tutorial style questions covering the subject in general which will be of ongoing interest to others.
Answer: There are several reasons for this.  A phase locked loop, or PLL, is a circuit that is used to generate a stable frequency that has a specific mathematical relationship to some reference frequency.  Specifically, it is a circuit that is used to control some sort of electrically tunable oscillator (usually a voltage controlled oscillator, or VCO) so that its output is locked into a specific relationship with a reference frequency that is supplied by some sort of stable reference (usually a crystal, crystal oscillator, or silicon MEMS oscillator).
A PLL works by dividing down the output of the VCO and the reference input with frequency dividers, then comparing the frequency and phase of these divided outputs and adjusting the VCO control voltage until the frequency and phase align.
It is possible for a PLL to generate a much higher frequency than the reference frequency - for example, a 100 MHz reference can be multiplied up to several GHz.  If the PLL is integrated on the same chip where the high frequency output is used, this can save power and reduce EMI by lowering the frequency that is sent through the circuit board traces.  It also makes the board layout simpler.
Since the relationship is determined with simple frequency dividers and it is quite simple to build programmable dividers, it is very easy to change the output frequency of a PLL by simply changing the divider settings.  This can enable power savings using a technique called dynamic frequency scaling, where the frequency is adjusted based on the required processor performance to reduce power consumption.  It also enables software-based configuration of the frequency, which makes the design of the system much more flexible as software can decide what settings to use at boot time based on detected hardware (for example, looking at CPU socket pin strapping or reading out SPD EEPROM contents on RAM modules during boot).
In a modern CPU, there are going to be multiple PLLs present for providing the clocks for various components.  Modern CPUs have a high level of integration and so components that used to be located on separate chips are increasingly integrated onto one die - there is a lot more than a single processing core and a front side bus on a modern CPU.  The processing cores themselves will run on one or more clocks that are supplied by one or more PLLs so the core clocks can be adjusted easily, and possibly can be adjusted independently.  The PCI express interface will also require PLLs, likely multiple PLLs to support operation at different link rates.  Serial ATA connections likewise operate at a different speed and hence will have their own PLLs.  Same goes for QPI, hyper transport, USB 3, HDMI, display port, etc.  The memory interface likely requires a different PLL to generate the specific clock frequency that the installed memory requires.  All of these PLLs would use the same (relatively) low frequency reference oscillator on the motherboard.
Comment: A critical issue you've missed is the difficulty of making a quartz oscillator above a few hundred MHz. Using a PLL allows the base frequency to be generated with high stability, then upconverted to GHz frequencies with little loss of stability.
Comment: @WhatRoughBeast: I don't think that's actually nearly as big an issue as moving the full frequency clock across the board without adding jitter and degrading edges.  No one works on solving the problem of higher frequency oscillators, because no one would buy the solution.
Answer: Been there, done that.
Apart from other reasons mentioned here is a different one:
The marketing guys want to make the chip design as cheap as possible. Thus they prefer to use cheap crystals. The ones use for Ethernet fall in that category. So you often end up having to use a 25MHz crystal.
At the same time marketing want powerful processors. Thus the processor (Let's call it a LEG++) should be able to run at 1 or 2 GHz.
The only way to do that is to use a PLL.
Or the processor can run at max 64MHz, but they want to have a USB interface which requires a 48MHz Clock. Again PLL to the rescue.
++LEG is not a registered trademark. (At least as far as I know)
Comment: @TomCarpenter: I worked for a company in Cambridge which had a text with the title *"ARM shows Intel the Finger"* on the wall. It was a beautiful 1'st of April article where they specified a one bit processor called "The Finger". Never found a copy!
Comment: LEG have just released a quintuple Toe version of their famous FOOT processor.
Answer: PLLs can be used to multiply and divide frequencies. CPUs that have PLLs to generate their clocks are highly reconfigurable. The clock speed can be varied relative to the external reference clock over a wide range, and it's the PLL that makes this possible.
Comment: Also it is not possible to get xtals to oscillate much beyond 100MHZ, so the ref oscillator needs to be multiplied many times to get 1 GHZ to 4 GHZ core frequencies. Core frequency is usually a integer multiple of the ref xtal.
Comment: Well, it is more generally going to be an integer ratio of the reference frequency, as the PLL can divide both the VCO output as well as the reference frequency.
Answer: PLLs are used primarily to generate one or more faster or slower clocks from a reference clock.
You might have say a fixed 100MHz crystal, but then want to run your CPU at 2GHz, so a PLL is required to increase the frequency (a 2GHz clock crystal isn't feasible).
Additional you may want to be able to change your CPU frequency on the fly (e.g. a turbo clock). In which case you could have a reconfigurable PLL.
Furthermore you may need a different memory or peripheral clock to your CPU clock. Again a PLL and divider can be used to generate this from a single reference.
Comment: One may want to refer to Wikipedia page of Standard Crtstal Frequencies: https://en.wikipedia.org/wiki/Crystal_oscillator_frequencies
Answer: 3 main reasons;
1) power savings for mobiles and extend CPU life keeping cool.
2) signal integrity is improved using xx multiplier for front side bus due to short wavelength, lower capacitance
3) flexible CPU speeds are possible with throttle on Clock multiplier and Vdd to allow burst CPU power and cool down.
Signal routing of 100MHz FSB is easy, > 1GHz is hard and your CPU is much higher, driver current increases with f and standing wave reflections distort square waves. While reducing CPU clock saves power and reduces temp.

Why is there a PLL in CPU?


Is it shirk to say Jesus lord

Question: One day on accident I said to my friends 'oh Jesus lord' it came out by accident. This happened almost a year now I asked Allan for forgiveness and forgot about it. Now it's ramadan and I have been thinking about sins that have done throughout my life. I feel like have committed shirk . But I do  believe in Allaah and the prophets (pbut) I believe that there is only one god (Allah)
Answer: No it is not considered shirk if it is said accedently. The prophet said:

Verily Allah has pardoned [or been lenient with] for me my ummah: their mistakes, their forgetfulness, and that which they have been forced to do under duress
40.39

So if it came out by mistake, Allah will forgive you Inshallah.
However, It is considered shirk if one says it intentionally as Allah says:

Indeed, Allah does not forgive association with Him, but He forgives what is less than that for whom He wills.
4:116
Answer: Although Ahmad Taher provided an excellent answer to the question, let me answer it from another point of view. I think it also matters how, why and in which meanings you have used the word "lord". For example, Cambridge English Dictionary defines the word "lord" as:
"a man who has a lot of power in a particular area of activity".
"to behave as if you are better than someone and have the right to tell them what to do: "
"in the UK, used to address a judge or peer"
"a title used in front of the names of male peers and officials of very high rank:"
For details see https://dictionary.cambridge.org/dictionary/english/lord
I do not think in any of the above mentioned meanings it is regarded as shirk.
Jesus is lord of Muslims as well in the sense that he is a prophet, a man of very high rank.

Is it shirk to say Jesus lord


manipulating in the viewport has suddenly become quite impossible

Question: I suddenly started to get the following error message: 'your system does not use 3D hardware accelation. Blender requires a graphic driver with OpenGL 2.1 support'. So I searched the internet and installed opengl32.dll. Blender is now opening again, but I'm hardly able to manipulate in the viewport. Blender is very slow to respond whenever I zoom or rotate in the viewport. Does anybody know a solution?
Answer: This really sounds like a driver issue. Maybe something got corrupted or deleted (it can happen that an antivirus, for example, deletes a critical component of a driver). You see, OpenGL usually is part of the GFX driver package for any graphics card because OpenGL is hardware-dependent and is integrated by the GFX card's maker. Just putting the file in there is not a solution--you're doing the equivalent of driving a car with a wheel missing.
For this reason, I recommend that you reinstall the current version or install the newest version of your graphics drivers. If you already have the newest, either try reinstalling or roll back to an older version if that is the cause (most likely it's not).
If you have an AMD card, download drivers here: https://www.amd.com/en/support
If you have an NVIDIA card, download drivers here: https://www.nvidia.com/Download/index.aspx
If this doesn't work, you may need to uninstall the drivers first (to avoid left-over files from conflicting with the new ones). Otherwise, an update should suffice.
Comment: Thank you so much for the explanation. I have an NVIDIA card, but I'm not sure which 'product type' to select under NVIDIA Drivers Download in your link.  Would you happen to know how to find out which download would go with my computer?
Comment: Sure. Press Windows key + R to bring up the run prompt. Then type in "dxdiag". Go to display tab up top (it may be named "monitor" instead) and check what your graphics card is. If you have an integrated, then find the monitor tab that has the dedicated NVIDIA card. That's how you'll know the model.
Comment: Thanks for your swift reply. Unfortunately downloading the driver hasn't done the trick. How do I uninstall the drivers? I'm not sure where they are located on my computer and how to avoid deleting important files. Sorry for my lack of knowledge when it comes to computers...
Comment: Ok, update--I've deleted my previous comment: I did research and here's my suggestion: after you installed the graphics driver, reboot your computer if it wasn't done already. Then go back to Blender's folder and remove that opengl32 file. Now try to run it. The issue with this is that you're essentially running OpenGL as Blender works (emulation), rather than having it run natively from your graphics processor's end. I should have mentioned this deletion part. Let me know the results.
Comment: You are a hero! Thanks a lot. All is working fine again.
Comment: Great. I thought that may be the fix. Glad to be of help.


How do I change my Roblox theme?

Question: I can't find the button that changes your theme to the OBC theme. Yes I do have Outrageous Builders' Club (OBC). I might be blind but I honestly can't find it.
Answer: Changing your theme on the ROBLOX website has sadly, been removed. This includes the OBC theme.
You can still use userstyle extensions to change the look of the website. Stylish has been recommend before, but it is now involved in some shady analytics and user data tracking by a company called SimilarWeb. There are safer alternatives out there, such as Stylus.
Answer: Roblox themes were removed, but you can get a browser plugin/extension such as Roblox+.
Comment: Roblox+ is also the only trustworthy one to my knowledge. Be aware of those that might hack your account.

How do I change my Roblox theme?


Unity Physics Trouble with Platform Objects

Question: Hi Game Development Community!
I'm new to designing in unity, and I'm having some issues with my player game object traveling through platform game objects. Several of my game objects (pink in pictured) are successfully acting as a surface for the ball (purple). But others (cylinders in white) are not. The ball goes straight through them. Yet I'm not seeing a difference in the cylinder and cube's physics settings I've set. Any advice or solutions to this problem are much appreciated!
Answer: Hey select the game object which is not colliding properly and check whether "isTrigger" is on , if it is then turn it off. Also make sure your collider size is covering the whole object.
Answer: The problem is with the Unity cylinder colliders. The unity cylinder collider isn't a cylinder but a capsule.
Uncheck the Mesh Renderer component of the cylinder and you will see the collider as green outline.
You need to add a mesh collider by clicking Add Component below.
I hope this sufficiently answers your question.


How can I customize new mail notification in alpine?

Question: I use alpine as my primary mail reader.  While I spend most of my day in the terminal or Emacs, it would still be nice to get pretty notification of new mail using notify-bin.  Is there any way I can configure alpine to run a custom command when new mail is received?
Answer: There is "NewMail FIFO Path" configuration option in alpine. Quoting the help:

You may have Alpine create a FIFO
  special file (also called a named
  pipe) where it will send a one-line
  message each time a new message is
  received in the current folder, the
  INBOX, or any open Stayopen Folders.
  To protect against two different
  Alpines both writing to the same FIFO,
  Alpine will only create the FIFO and
  write to it if it doesn't already
  exist.

So, I set the option to '/tmp/alpine.fifo', and wrote simple utility to read messages from the FIFO and invoke 'notify-send':
<code>#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>

#define FIFO_NAME "/tmp/alpine.fifo"

int main(void)
{
    char s[512];
    char cmd[512];
    int num;
    int fd = open(FIFO_NAME, O_RDONLY);
    do {
        if ((num = read(fd, s, 300)) == -1)
            perror("read");
        else {
            s[num] = '\0';
            sprintf(cmd, "notify-send -t 0 'New mail:' '%s'", s);
            system(cmd);
        }
    } while (num > 0);

    return 0;
}
</code>
Save it to alpine-notifier.c, and compile with 'gcc alpine-notifier.c -o alpine-notifier' command. Start 'alpine-notifier' after alpine is started. Enjoy pop-up notifications.
Comment: @steven: I'd vote for it if you'd be kind enough to share it. :-)
Comment: nice solution :-)
Comment: Awesome.  I wrote a small shell script to do essentially the same thing.
Comment: Nevermind, I ended up writing one as well.
Answer: Update:
I wasn't satisfied with my previous answer, so I improved the script a lot and made a github repo for it.
Now you don't have to start the script after starting alpine, the script will take care of everything for you. The core of the script is mostly the same (I only improved parsing a little):
<code>#! /bin/bash
while read L; do
    n=$(($n + 1))
    if [[ n -gt 3 ]]; then
        name=`echo "$L"  | sed 's/  \+/\t/g;s/^\(+ \)\?\([^\t]*\)\t\([^\t]*\)[\t ].*/\2/'`
        subject=`echo "$L"  | sed 's/  \+/\t/g;s/^\([^\t]*\)\t\(Re: \?\)\?\([^\t]*\)[\t ].*/\3/'`
        box=`echo "$L"  | sed 's/  \+/\t/g;s/^\([^\t]*\)\t\([^\t]*\)[\t ]\([^\t]*\).*/\3/'`
        notify-send -t 10000 $iconcommand "Mail from $name" "$subject\n-\nIn your $box."
    fi
done < <(cat alpine.fifo)
</code>
The rest of it is a little large to post here, so anyone who's interested can just get it at the repo.
Comment: Bruce, thanks for sharing the script! Now I know how to read and process messages from FIFO while keeping it open in shell. Could not figure it out while setting up a notifier for myself :)
Comment: @Linulin Cool. =) Unfortunately the filters I used for setting `content` and `name` are a little buggy in some cases., which is a little silly since they're the reason I posted the answer at all. =P
Comment: It is awesome to see shell used so well.  Thanks for posting it on github.  Bravo!
Answer: Can't you use a specialized mail-notification tool like Gnubiff, mail-notification or kbiff?
Comment: I would like to use mail-notification to achieve something similar, however I cannot find any documentation on how to customize the mail-notification new-mail command.
Answer: It is not possible to customize the "new mail notification" of alpine.
There is no such option mentioned in the configuration documentation.
Also here is a quote from the mailinglist from Eduardo Chappa:

I've noticed that alpine gives a visual alert in gnome terminal by
    flashing the screen, when a new mail arrives. Is there any way to
    customise the alert, so that, for instance, it plays a sound or
    something?

[..]
Alpine, as you can guess now,
  will only beep. In Web Alpine it is
  possible  to send a file to be played
  (to the browser) for new mail
  notification.  There is no such
  feature in Unix, Mac or Windows
  Alpine.

Your options are now:

write a feature request to the alpine-info mailinglist
get the sources and write a patch
use an external tool like Mail Notification

And to quote the developer of my favorit mail client:

All mailclients suck...

:-)


What is world building?

Question:
personal psychological architecture / brain wiring ?
society ? Our connection with others?
natural world ?
what kinds of worlds ?
Comment: Worldbuilding is about building worlds and everything it contains. It is as simple as that. You can have a look at the tour http://worldbuilding.stackexchange.com/tour or some of our popular questions to have a better idea http://worldbuilding.stackexchange.com/questions?sort=votes
Answer: Worldbuilding is a forum for (real) people who want to build (fictional) worlds, and run into problems of certain types, mostly about the general background and not specific actions of specific characters.

Society can be an issue if you find the right question, e.g. What sort of punishment would replace fines in a post-scarcity society?
The natural world of the setting can be an issue if your find the right question, e.g. Would a planet made completely of water be possible?
Psychology can be an issue, as long as it is not plot development, e.g. Could an unusually long lived being continue to learn with the times?
Comment: Creative and insightful reply.

What is world building?


Identify anonymous mobile phone user by network participants

Question: I have wondered this for quite some time but have not found any references. In the TV series "The wire" they use disposable prepaid mobile phones as a counter-surveillance technique. However if someone uses a prepaid mobile phone and connects to the same people as with his old phone, wouldn't this uniquely identify him? For example if Alice knows Bob and also Eric, while Eric lives in a town far away. Now Alice buys a new burner phone and still messages with Bob and Eric, what are the odds that another network user who is not Alice knows Bob and Eric too? I mean only knowing two people - even if Eric lived in the same area as Bob - will greatly reduce the number of suspects. Is this technique used? And where can I read up on it? I'm interested in the technical as well as legal aspects of this method.
Comment: I think you're referring to the NSA meta data collection program. They did exactly this and it made a lot of people mad. The argument is, they're collecting "anonymous" meta data on people. However, as you've pointed out, it's easy  to correlate that data if you have enough of it. As a side note, the trick with burner phones is to use them for something and throw them away. Not call your mom and bff lol
Answer: Is this technique used?  I can't speak specifically to mobile phones, but in general, it's a regularly used technique usually referred to as de-anonymization or re-identification.
One common legal application is in web advertising.  Advertisers aren't allowed to have access to your personally identifiable information, but they may have access to your anonymized information and some unique identifiers (usually from cookies or browser fingerprinting).  Those unique identifiers can become lost or replaced as cookies expire or are deleted, but by cross-referencing patterns and other anonymized information, it's sometimes possible to draw a conclusion that two different unique identifiers are actually the same individual.  In the advertising world, this can be used to identify that two seemingly different people are actually the same person using different devices (e.g. mobile phone, desktop, tablet) without ever actually knowing who the individual is.
That said, it's not always an easy or foolproof process, but it is possible.


In Nethack3.4.3, can an altar be wished for?

Question: I've been playing 343 for a while, even read the wiki as best I can, but can't find an answer to this.  I have an Elven Priest that has been to Sokoban (BoH) and found the quest portal but still haven't found an altar.  I have 7 cursed scrolls of create monster that should help me level up for the quest, but I'd hate to waste all the potential sacrifices.  I have 2 blessed magic lamps, and a bones pile has supplied SDSM, MR cloak, Macicbane, and Stormbringer.  Being a priest I'd like to unrestrict at least one of the weapons...Short of running all the way to minetown, I'd like to wish for an altar near the Quest portal. Is such a thing possible or would it just waste a wish?
Comment: There is a guaranteed altar in the Dwarven Mines, though if it's cross-aligned, converting it might be a bit tricky.
Comment: Well, it works in debug mode. That does **not** guarantee it will work in normal mode. If you do try it, be sure to specify the alignment of the altar. For example "chaotic altar", otherwise it might be cross aligned.
Comment: Given that altars are (generally) not rare.  The priest in the mine town and his available protection is generally more valuable than converting the altar.  I'd only attempt it if there were *no* other altars above the castle *and* I'd not found any holy water.  Not for the chance of the largely mediocre Sacrifice Gifts.
Answer: Chasing through the source code, the function readobjnam() in objnam.c is responsible for translating object name into internal game structures, and determining what you can (and can't) wish for.  Altars are in the "wizard-only" section of the function, along with traps, fountains, and other dungeon features:
    if (wizard && from_user) {
       ...
            if(!BSTRCMP(bp, p-5, "altar")) {
                aligntyp al;

                levl[u.ux][u.uy].typ = ALTAR;
                if(!strncmpi(bp, "chaotic ", 8))
                    al = A_CHAOTIC;
                else if(!strncmpi(bp, "neutral ", 8))
                    al = A_NEUTRAL;
                else if(!strncmpi(bp, "lawful ", 7))
                    al = A_LAWFUL;
                else if(!strncmpi(bp, "unaligned ", 10))
                    al = A_NONE;
                else /* -1 - A_CHAOTIC, 0 - A_NEUTRAL, 1 - A_LAWFUL */
                    al = (!rn2(6)) ? A_NONE : rn2((int)A_LAWFUL+2) - 1;
                levl[u.ux][u.uy].altarmask = Align2amask( al );
                pline("%s altar.", An(align_str(al)));
                newsym(u.ux, u.uy);
                return(&zeroobj);
            }

Answer: You can only wish for items, and an altar isn't an item. Wishing for an altar won't work.
Comment: I believe you can wish for an altar on Wizard mode, and specify the alignment, but you're correct for normal games.
Answer: You seem to have two issues:

As others have mentioned, the answer to your direct question is that altars can't be wished for outside of wizard/debug mode.
If your level isn't high enough for the quest yet, I encourage you to continue exploring downward.  There's a good chance you can still find an Altar Room or Temple before hitting the pre-castle mazes.  Otherwise, let's be honest, the walk from the quest portal to the mine-town really isn't all that far in the grand scheme of the game.

Unrestricting Magicbane or Stormbringer:
There are two ways of unrestricting a class of weapon.

Gifts in response to Sacrifice at a co-aligned altar:
You're an Elf, therefore Chaotic.  The good(?) news is that you are eligible to receive both Grimtooth and Sting as a technique to unrestrict Daggers, and thus Magicbane.
Stormbringer on the other hand is the only runesword in the game; as it already exists in your game, you can't be granted another.
From the information you've provided, your gift opportunities seem to be:

3 chances at a longsword.  Hope for Frostbrand, one of the two highest damage weapons in the game.  If you get one of the others, Wish for Frostbrand.  It's the only Artifact on this list you really want anyway.
2 chances at a dagger.  They both stink, but at least they unrestrict Magicbane
Orcrist, an Elven Broadsword, but hey, it's a 1/9 chance to unrestrict Stormbringer.
The war hammer Ogresmasher, a crap weapon that you can become Expert in.
The Morning Star Trollsbane, an only slightly better weapon that you can become Expert in.
The Silver Saber, Werebane.  You've already got decent silver damage covered as you're already able to make Skilled with the Silver Spear, but at least this unrestricts saber if you want to wish for Greyswandir, the game's other big damage weapon.

As a game's artifact count makes wishes for other artifacts (such as other class' Quest Artifacts) less likely to succeed, and the difference between Unskilled and Basic skill levels becomes trivial at higher experience/luck levels; I'd probably not spend too much time sacrificing for junk artifacts.
Crowning:
You already own Stormbringer which is the default Crowning Gift for Chaotics.  This means that when/if you are crowned, whichever weapon you are currently wielding will (among other things) be unrestricted.  Best of all you don't need an altar to be crowned, just high alignment & luck stats.  This may be one of the rare instances in which Crowning may be "Desirable".
Though if you plan to be crowned, you may just consider cutting out all the Sacrificing and just wish for either Frostbrand or Greyswandir while your game still has a low artifact count...


What is the difference in the pivoting strategies between LAPACK's dpstrf and dpst2 and why?

Question: dpstf and dpstrf sometimes give different pivot results. Of course I can read the source code, but I don't get the idea from it. Since pivoting is for stability of the Cholesky decomposition, one of them is more stable. Which and why does the other exist?
Answer: The difference is which BLAS level they are utilizing. TRF is BLAS3 and TF2 is BLAS2. BLAS level 3 routines, roughly speaking, optimized for computers with cache memory such that they can perform block calls. BLAS 2 is optimized for vector computers with possibly shared memory.
As you can see in the code (line 209), if the optimum block size turns out to be either larger than the matrix size(which implies the impossibility of blocked algorithm) or less than or equal to 1 then DPSTRF falls back to the unblocked version DPSTF2.


The illusion of 3D sound in Audacity

Question: I am looking for a way to make audio sound like it's above your head and then below your head in Audacity. Is there a way to accomplish this?
Answer: Investigate Ambisonics and Binaural sound. Audacity won't help you but you should investigate Reaper with the Ambisonic Toolkit.
Answer: Like Mark mentions, you should have a look at Ambisonics and/or Binaural (HRTF) sound. Additionally, you could also have a look at techniques like VBAP (Vector Base Amplitude Panning) and DirAC (Directional Audio Coding), which are meant to be used for multichannel reproduction, but they could also be used for speaker emulation in binaural rendering. For more info on those techniques you could start with:

VBAP
DirAC
Ambisonics
Binaural Audio

Finally, please keep in mind that Audacity is just a tool and it won't necessarily provide a solution to all your problems. As long as you understand the underlying principles and phenomena of your problem you may be able to use Audacity (or any other Editor or DAW) to achieve what you intend to do.

The illusion of 3D sound in Audacity


QGIS Print Composer PDF creation text issue

Question: I am noticing some outline/shadows when I export my print composer to a PDF. Specifically the text within my legend looks as it does in the image linked below. Has anyone else had this issue or know how this can be addressed?
Answer: When you export a layout as a PDF, QGIS can either export all the content as a raster (i.e. an image embedded in the PDF, so when you zoom in or save in low quality details and edges look pixelated), or some/all elements - typically text - as vectors (so that you can zoom in as much as needed without seeing quality degradation).
It looks as if your PDF might have been created with all the content rasterised ('Print as raster').
Try the following:

In the Map Layout window, under the Layout tab (or on the menu bar, Layout > Layout Properties), scroll down to Export Settings. Ensure the 'Print as raster' box is not checked.
When exporting as PDF see if setting 'Text export' to 'Always Export Text as Paths (Recommended)' fixes your issue.

And if not printing as a raster causes your file to be too large, check the Export resolution settings under Export Settings - try 150 dpi instead of the default 300 dpi (and maybe turn off Always export as vectors - this is not the same as unchecking 'Print as raster') If your text is being exported as paths as mentioned above, then it should continue to appear crisp.
Note that as Vincent mentioned, if you have opacity in your layer style and click OK when the warning message pops up about exporting with non compatible print styles, it automatically activates 'Print as raster', so you should be vigilant about whether it's been selected even if you don't remember enabling it yourself.
Answer: How do you export you print composer?
How are set your layer styles?
What's the size of the map / pictures?
For example if you use opacity for layer style, when you export you print composer, QGIS export it as raster, so as an image.
For example in this case it's seems to be normal to have some quality degradation, pixels pictures comes with lowest qualtity.
Try to export in vector format.
Comment: I have been exporting as PDF, would you suggest Export as Image or Export as SVG? Images are exported as 28x20 inches and the only issue is the legend which is 3.6x7.8 icnhes and uses 8 pt font. Sorry I am not familiar with what you mean by vector format?
Comment: Don't be sorry, we are here to learn.

Depending on your qgis version, better use the latest LTR, when you export as pdf and you use opacity effect for layers, qgis ask if you want to export it as vector or image.

I think you result would be better in vector format.

To be short,
a image as rasster is composed by pixel, each one with a colour.
a vector image is composed by elements (points, lines and polygons) defined by coordinates; no matter how much do you zoom, you will always have the same definition.
Comment: If you use raster image, there is, at some point compression with your image, so when you zoom you have a "worse" quality image.

Depending on your final objectives and means, you will choose vector for printing, but for example if you print small format with a low print quality it's not's much better than using raster image with pixel.

Using small font may be also an cause of your problem.


Which US coin type has more older coins in circulation?

Question: Which US coin type (as in Quarters, Cents, Dimes, Nickels, Half Dollars, etc.) has the most old coins out of all in circulation?
Answer: Randall Munroe, in his What If? article All the Money, claims that of all the coins in the world, there exists more of the U.S. penny than any other coin.  His estimate of about 150 billion pennies currently in circulation is based on a 1996 General Accounting Office report on the future of the penny that cites a U.S. Mint estimate of 132 billion pennies in 1996, as well as the annual production numbers of the Mint.
Comment: Very few dimes, quarters, and half-dollars older than 1965 are in circulation, because pre-1964 coins were made of silver, and have been deliberately removed from circulation.  Five-cent pieces have had the same design for the longest period (since 1938/9), so are least likely to be noticed by the casual observer as "old" or "collectable".  Even people not generally interested in numismatics may hold a wheat-head penny if they happen to get one in change.
Comment: Yes but I'm talking about old coins. Which type of coin has the most older (1960s or older) coins in circulation. I am guessing that this suggests the answer is pennies, but can you clarify.
Comment: @Guy What made you pick 1960s as the definition of "older"? Why are you interested in coins of this age? Please edit your question if you have more information you wish to include in your question.
Comment: After testing (with about 20 rolls), with pennies there are considerably more 1970 pennies than 1960s. Even in quarters, pre-1964 have the mint mark inverse. I wonder which type of US coin has more older coins that the other types (I consider 1960s and pre-1960s older).
Comment: Also I made a mistake. Pre-1964 quarters have the mint mark on the reverse of the coin not the obverse.
Comment: Randall Munroe gets -1 for not using the word "molassacre"


Books to begin Husserl's Phenomenology

Question: I wanted to learn about Husserl's Phenomenology and was wondering on what a good place to start would be? I have in front of me The Essential Husserl, Basic Writings in Transcendental Phenomenology and the Cartesian Meditations. I don't mind digging through something that's somewhat technical, with that in mind any suggestions and comments on the two books mentioned above?
Comment: Can't comment on those texts since I haven't read them. I read Introduction to Phenomenology by Robert Sokolowski. Really liked that book: http://www.amazon.com/gp/product/0521667925/ref=pd_lpo_sbs_dp_ss_1?pf_rd_p=1944687462&pf_rd_s=lpo-top-stripe-1&pf_rd_t=201&pf_rd_i=0415183731&pf_rd_m=ATVPDKIKX0DER&pf_rd_r=08J2QNM53DT1A4BWAJW7
Answer: Of the three texts you have,
I think the easiest place to start will be with the Cartesian Meditations.
Husserl studies is a messy business with subtle differences in the nature of the epoche and bracketing between texts, but the CM is a good starting point because you know (or should know what to compare it with): Descartes.
Bring to it the basic task of abstracting away from the modern obsession with knowledge deeply linked to metaphysics and moving towards what we can learn through impressions as they occur for our conscience and you've got a good start to reading a thoroughly challenging text.
I don't know which texts are captured in The Essential Husserl, but I would guess it contains key excerpts and is designed for classroom use. It may have a very helpful introduction you may want to read even before CM.
Basic Writings in Transcendental Phenomenology is anything but "basic" under the meaning "easy or simple" but rather is about what is fundamental to transcendental phenomenology for Husserl.

Books to begin Husserl's Phenomenology


Work done on a gas enclosed in a container

Question: According to everywhere work done on system of a gas is equal to $p\,\mathrm dV$ but here $p$ is just the external pressure. Shouldn't internal forces be considered while calculating work done thus giving a place for internal pressure as well?
Shouldn't the $\mathrm dW$ be equal to $(p_1 -p_2)\,\mathrm dV$ where 1 is internal and 2 is external?
Comment: For all cases, at the boundary between the system and surroundings, $p_{int}=p_{ext}$.  However, for an irreversible process, the value of $p_{int}$ at the boundary is not given by the ideal gas law.  The ideal gas law only gives the correct value for reversible processes (close to thermodynamic equilibrium).
Comment: Why do you think $p$ is the external pressure?
Comment: Like when it is done in the case of irreversible process and in case of reversible process p int=p ext
Comment: Why did someone down vote this please clarify
Comment: I know but why we don't take the internal force work done which is exerted by internnal pressure
Comment: Like I said, at the boundary the internal force is equal to the external force.  We just don't know how to determine the internal force for an irreversible process, since we can't use the ideal gas law for an irreversible process (except at the initial- and final thermodynamic equilibrium states).
Comment: Do you think that in a rapid irreversible expansion or compression, the internal pressure of an ideal gas is described by the ideal gas law $p_{int}=\frac{nRT}{V}$?
Answer: I want to explain this usage, i.e. why use internal pressure, by using a container with a piston as an example. You can make similar thinking for other and more general case.

If we take a look of the piston, it has 3 forces on it: external pressure, internal pressure and frictional force on its perimeter interface with the container wall. For most problems, we assume there is no friction and the piston moves very slowly. That means frictional force is zero and acceleration is negligible.
A free body diagram can tell us that the external pressure equals the internal pressure.
Work is the multiplication of force and piston travel distance. Thus, the external pressure produces the same amount of work as that from the internal pressure but with opposite sign.
Now, in a more generalized case, where friction cannot be ignored, the work done by the external force would not be the same as the work done by the internal pressure; there is an extra work done by the frictional force.
By whatever way, work done by the internal pressure is completely used for or by the gas system whereas work done by external pressure involves extra work such as that from frictional force and cannot be directly used for gas system calculation.
If it is not a piston container system but a gas gan, when you squeeze the can by using very high external pressure, the work done by the external pressure, in this case, includes the can plastic deformation energy.
To be simple and less prone to make mistake, textbook tells people to use internal pressure for gas system calculation. If you want and you are very clear in mind on the force involved in your system, you can use external pressure for work calculation. Just be careful about the extra work and the sign of the work.
Note $(p_{external}-p_{internal}) \times dA$ is the force on the piston.  $(p_{external}-p_{internal}) \times dV$ is meaningless as the external pressure is not directly applied on the gas.
Comment: Got it thanks. I had to tak3 the gas as system but I was taking gas and piston as system
Answer: First of all, if you are talking about the ideal compression where $P_{ext}$ is just bigger than $P_{int}$ by $dP$.
Secondly, when we learnt Newton's laws, we do agree that when we talk about forces acting on a body, we do not take the forces acting by the body on other things. The pressure $P$ applied externally is intended to cause a change in volume of the gas.
There won't  be sense to actually talk about internal pressure involved in cancelling this effect off. $W=\int PdV$ is in fact, just a re-written form of:
$$W=\int Fdx$$ $$=\int PAdx$$
$$=\int PdV$$
To make it clear. This is no isothermal or adiabatic compression. This is only a constant pressure use. True, that the internal pressure will change, but we always assume that the external pressure is just equal to the internal pressure.
Comment: That's Newton's law while considering acceleration of a system but in the case of applying work energy theorem we take work done by internal as well as work done by external
Comment: The gas does not lose energy in this process at all. It gains energy. And only due to an external force.
Comment: i think there is communication gapp here. I am asking why the work done by internal force is not counted here??
Comment: When you use the first principle of thermodynamics, only external work has to be taken into account.  It is complety different from the work energy theorem in which you take into account internal and external work.
Answer: At the interface between the system (say, the gas) and the surroundings (say, the inside face of the piston) where work is being done, the "internal pressure" of the system is always equal to the "external pressure" of the surroundings.  And, in a reversible process, the internal pressure can be determined by the ideal gas law (or other equation of state, say, for a real gas).
However, in an irreversible process, the gas is not at thermodynamic equilibrium throughout the process. And, since the ideal gas law (or other equation of state) is correct only at thermodynamic equilibrium, the internal pressure of the gas at the boundary where work is being done cannot be correctly calculated using the ideal gas law.  This is because viscous (dissipative) stresses also contribute to the internal pressure at the interface in the case of an irreversible process.  As a result, in irreversible processes, the internal pressure depends not just on the gas volume and temperature but also on the time rate of change of gas volume.  So the ideal gas law can't be used.  For an irreversible process, we can determine the work done only by controlling the interface pressure externally, say by using an automatic control system or by removing specified weight from the piston.


Sending signals to USB port using C

Question: I want to send a simple 5V signal to the usb port. The USB cabel's insulation will be removed and connected to a relay which is connected to an electric door system. I think I should write this code in C. Can somebody give me a hint?
Comment: 5v signal to the usb port? Not sure I understand what you want.
Comment: okay, electronics are not my specialty. I need to send a signal from the usb port to the usb cable. Thats all, nevermind what I said about 5V earlier :)
Comment: How about a USB to Serial device and just control one of the signals like Ready to Send, or similar?
Answer: You cannot do what you want with just connecting a relay to the USB port.
The USB is a bus, with a serial protocol running on it.  It is necessary for you to interface with that bus using the proper protocols.
You will require a use "device" which is capable of being programmed to respond to a computer-based stimulus, and activate an external signal.
There are many ways of achieving this, from ready-made products, through DIY kits, and al the way to discrete ICs that you can use to build your own system.
Personally I would recommend one of the many DIY kits available, such as the Velleman K8055 USB Experiment Interface Board.  There are many others like it.
If you want to get in to the nitty gritty, then you need to be looking at such things as Microcontrollers (which the Velleman is based on), which can be programmed to do many different things.  Some of these have built-in USB support, but it takes quite a lot of in-depth knowledge of the USB protocol to get to grips with these.  Most people use an "FTDI" chip to convert the USB into RS-232 first.
If you are wanting an off-the-shelf product then you may want to look at the possibility of a USB Parallel Printer Port product, that you can program and access as if it were a parallel (Centronics) port directly attached to your computer.  This would give you 8 outputs you can turn on and off.
One more thing to watch out for though - most computer / microcontroller outputs won't be powerful enough to directly drive a relay.  You will need to feed the signal through some "driver" circuit to achieve enough power.  This may be as simple as a single transistor, or you may be looking at something more complex such as a MOSFET, etc.  Oh, and beware of "Back EMF" - a relay is an "Inductive Load".
Comment: @user5369 - The Ethernet port, like the USB port, is not a single-ended signalling system.  Signals are sent down the line using differential currents, not by making the line high or low.  Parallel printer ports and RS232 serial ports are about the only connectors you're likely to find on your PC that use single-ended signalling that you could set "high" or "low" as you desire.
Comment: Is possible to use the RJ45 just for sending a signal? or do I have to use a microcontroller?
Comment: The RJ45 is an Ethernet port - that also has protocols and signalling to worry about.  Just as complex as (if not more so than) USB.
Answer: USB is not as simple as you seem to think it is. USB has a communication protocol that doesn't allow you to simply output high or low.
Probably the simplest way to do this is to use a microcontroller connected over usb using a serial to USB method. You can use an FTDI chip to do this. After connecting to the FTDI chip the computer will install a virtual serial port. You can then send data to this serial port and the microcontroller will receive it over UART. The microcontroller can then read in the packets you send and you can have 1 packet for 'on' and another for 'off'. The microcontroller would just turn a pin high or low based off of the last packet it received.
Another option to consider would be to use the serial port directly. Many computers give you control over the clear to send type pins. If you can get this ability then it would just be a matter of having a program that toggled the clear to send state.
Answer: USB is a sophisticated serial bus which allows communication between a host (your PC) and up to 127 devices (all kinds of products you connect to your PC). So it appears that you don't have direct access to the bus, anyway that you can't simply switch on and off things with it. But there is a number of solutions to this.
PCs come with ever less EIA232 (often referred to with its old name RS232) ports, but sometimes you need one. A few companies specialized in interfaces, so-called bridges, which convert the USB bus to EIA232. FTDI is a well-known manufacturer of those bridges, and in other answers it's been suggested to use EIA232 control signals to control a relay. This may work, but in fact it's improper use of EIA232.
A less known product of FTDI is the FT245R USB to FIFO converter, which allows you to control general-purpose I/Os via USB. This product from DLP Design is a ready-for-use module based on the FT245R.

Use one of the I/Os to switch a relay via a transistor. (The I/Os can't deliver the required current to drive the relay directly.)

See also this answer to a related question.
Answer: Directly switching 5v would only be possible if you had low-level programming information and access rights for the USB PHY or hub chip, ie, the ability to enable/disable the 5v VBUS (and to do so specifically for a particular port, if you need to keep other devices such as a usb keyboard working).
There are definitely systems on which this would be possible (the lone USB port of a tablet I was playing with recently, for example), but it's a very implementation-specific and non-portable hack.
Most of the time, the suggestions everyone else is giving you to use a USB-I/O chip such as an FT245 or USB-enabled micro-controller or even ready-to-go USB-relay board are preferable, since they work via drivers that rely on the standard USB protocol and do not depend on intimate knowledge of particular chips used to implement the host interface or hub.
EDIT: I'm trying to recall, there may actually be standard commands for enabling/disabling VBUS of specific downstream ports on a hub, but in practice few hubs actually have the necessary power switching device to implement that.  Finding one that does may be no easier/cheaper than buying the USB-relay board.
Answer: As others have pointed out, USB is a bus, so you need to use a device on the other end to translate bus commands into physical actions. The easiest way to do that is to use a number of existing products designed for this without needing to write code for the embedded end - for example, Phidgets have a whole range of devices - this relay board is probably what you want.
If you're prepared to learn a little embedded programming, an Arduino or a teensy could provide more affordable and hackable options.

Sending signals to USB port using C


In a DBMS what are the implementation details that make set operations faster than cursors?

Question: What are the low level implementation details that make set based operations exponentially faster than iterative processes, like cursors?
At a memory level how does a set operation "touch" the data less than a cursor?
Answer: Set-based operations are iterative at a "low level", and are not necessarily any faster to execute than cursors under all circumstances.
The main advantage with set-based operations is that they are well-defined operators which can be analysed algebraically, and the order of operations thus rearranged or simplified by the database engine, or the exact algorithmic implementation altered - not just at the time of writing the query, but possibly later at the time of subsequent executions of the query.
What is "simple" or "fast" here is constantly re-determined by the database engine at runtime based on the statistics it collects about actual whole database performance.
By contrast, there is much less flexibility for the database engine in the case of cursors, and if every action in a database were written as a cursor then overall performance could become abysmal (or the system more recalcitrant to any changes) far sooner than when set-based operations are used which provide the database engine a large latitude for optimisation.
The most straightforward analogy is the performance of a modern optimising compiler for a high-level language, versus writing everything in assembly language, although this does not quite capture the ongoing monitoring that a database engine performs.
Answer: When operations are made on sets, this is what DBMS engine is optimized to do, all fancy stuff like collecting minimal intersection from queries, order execution, batch reads and possible concurrency kicks in.
Per row query could be executed by multiple threads, splitting work among them, when you create cursor processing must be sequential. By the nature of temporarily created set, it differs from internal structure by allowing iterator-like traversal, so it is effectively new table populated with result. When query is executed all updates are issued, so even not altered data (in the cursor) is updated back, this creates more work - the price for easier result traversal.
No possibility for parallel execution is constant slowdown, creating temporary memory is operation with huge constant, updating results is wasteful, but this creates another passes through data, so slowdown is polynomial with one-thread processing and additional memory management.


Could a bottle rocket be up scaled to achieve orbit?

Question: Could you construct an orbital stick stabilized rocket, by scaling up a firework?
Comment: I dont see why this is marked as a duplicate, really. Neither the water-rocket to space question or its highest-voted answer mention scaling up the solution. They deal with using multiple small bottles. This question explicitly asks if scaling upwards is a valid strategy, which is as aspect NOT covered by the other questions.
Comment: Still a dup of https://space.stackexchange.com/questions/30972/how-would-a-long-pole-be-transported-to-space If you're not even going to remember your own questions...
Comment: Muze, very often people need to come in and ask comment questions to get clear what you actually mean. Then there are a lot of edits, and the question sometimes completely changes correction. Not to mention the *on hold* / *reopen* cycles it then goes through. Is there something you can do to prepare your questions better? Hint: Ask that on the meta site.
Comment: updated to chemical not water
Answer: The classic bottle rocket design is optimised for stability during launch at low cost. The stick part both acts as a launch rail and keeps the center of drag well aft to prevent tumbling. The cost of this is weight since you effectively fly with part of your launch system still attached and the drag could be achieved with fins or avoided entirely with thrust vectoring.
So for any rocket with active control there is no advantage, and for uncontrolled flight fins and a launch rail will get more out of the same engine.
If the objective is to fly a long structural element as the payload itself then it becomes a bit different, since there are structural problems with flying a long thin structure on top of a long thin rocket so putting it alongside might be made to work. It will produce more frontal area and thus drag but may allow a lower rocket structural weight since loads from the high thrust stages can be directly applied to the spar rather than through the upper stages.
You probably would not want the spar extending past the first stage engines, both because of the heat effects and because it will block the thrust vector you need to keep thrust through center of mass, even if you have a twin structure your engine out modes may require vectoring through the spar/s unless you are launching enough of these things that simpler design can be traded against a percentage crashing (if this question is part of OP's series on space elevators).
Stage separation also becomes much more complex since you need to avoid striking the payload spar.
Comment: @Innovine I'd say they said "no", a simple non-staged bottle rocket would have to be gigantic to make it to orbit, possibly a fraction the size of the earth itself due to the rocket equation. It's basically a giant solid-fuel single-stage booster. Can it escape the atmosphere without being massive? Yeah. Achieve orbit? Probably not.
Comment: @Innovine - probably not helping is that I grew up in a time and place where bottle rocket is https://en.wikipedia.org/wiki/Skyrocket, not a bottle full of water under pressure.
Comment: Not actually answering with a yes or no though
Comment: Yes it would be gigantic. That is the question: does it scale up? Absolutely. If it doesn't leave the atmosphere, make it bigger. Make it big enough so it sticks out through the atmosphere. Make it so 99% of it is already above the atmosphere if you like.  you can't answer a question on "does it scale" with "no, cos it would be gigantic".
Comment: @GremlinWranger I don't think the choice of propellant plays much of a role, really. The concept of scaling up until orbital velocity is reachable applies to both solid fuel rocketry as it does to pressurized water rocketry. The efficiency is certainly different though, which probably explains why the shuttle boosters didn't use water :)
Comment: @Innovine No. Square-cube says you can't scale it up like that.
Answer: Based on Single-stage-to-orbit, I don't think so. This article quotes Robert Truax who said that the structural weight needs to be aggressively minimized for SSTO, which is what your question asks about. Bottle rockets use paper as the main component of their structure, and that's not going to be strong and light.
EDIT
With the change "Materials would not be the same of course..." The issue is still that SSTO is hard, and multiple stages offer advantages over a single. For example, from that same Wikipedia article, the stages can be engineered to maximize efficiency for their particular role in the trajectory of the flight. You'd get much more bang for the buck by making a two-stage bottle rocket than a large single-stage rocket.
Comment: ¯\\_(ツ)_/¯ welp...
Comment: +1 was from me. Thank you for answering.
Comment: I think OP is looking for ways to send very long poles into orbit, SSTO or 2STO, rather than literally trying to scale up a bottle rocket.
Comment: OP says, "Could a bottle rocket be up scaled to achieve orbit?" Yes, that's the larger goal. This question asks whether scaling bottle rockets is a way to do that.
Answer: Yes.
The physics involved in thrust are independent of scale. A bottle rocket that is three hundred kilometers high and 100km in diameter will blast off and into orbit with little difficulty.
The problem is if we can make one big enough. The answer to that is no. Can we successfully launch one without destroying the surface of the Earth? Probably not.
Comment: I think it will be really good if you put your calculations to back up your answer.
Comment: The physics of thrust are (generally) independent of scale, but delta-v doesn't scale up.
Comment: Nor does it need to.
Comment: No math is needed. Lets look at the extreme end of the scale. We have a bottle rocket 10 times the mass of earth. Are you suggesting it can't get into orbit (elliptical motion around the barycenter)??
Comment: An interesting calculation might be whether there is enough water on the Earth to fuel the rocket. I suspect not by an order of magnitude.
Comment: @Innovine If you have a bottle rocket 10 times the mass of the Earth and light it doesn't go anywhere--the exhaust velocity is less than the escape velocity of the rocket, the exhaust falls back, no thrust.
Comment: I'm not convinced this is true. The rocket equation is pretty much scale-invariant, isn't it? it's only drag that gets better with size, no?


How do you know if you believe in Allah?

Question: For the last few months I have been doing a great deal of reading and research about Islam, listening to lectures, and reading through a couple translations of Qur'an. From an intellectual/rational capacity it all makes sense to me. Learning about Islam feels like coming home after a long absence. But I don't really know what it means or what it's like to believe in God. How do you know if you believe in God, or how do you learn to believe?
Comment: I think to believe in Allah means to put what you have learned so far about Islam into action. So you would want to please Allah by obeying Him and avoiding sinful acts and you would wish to come closer to Him and speak to Him by establishing prayers. You would feel love for Allah developing in your heart and you feel happy when you hear recitations of the holy Qur'an or supplications .You thank Him for everything He has given you and when you are in need you only ask Him for help. To learn about Allah intensifies your belief.             https://www.youtube.com/watch?v=ufKcMpIJpB0
Answer:
There is no god but God. Muhammad is the messenger of God. (Shahada)

If you believe that you actually believe in what you said, then you're a believer.
Other definition could be -

This world is a prison for the believer and paradise for the non-believer. (Muslim)

For sure there forms and levels of hypocrisy, e.g. Qur'an 4:142, you should check them out.
Allah knows the best.


Postgresql in DevOps skills

Question: What are the basic skills and requirements a DevOps candidate should have when working with PostgreSQL?
How to monitor it, deploy, etc.?
Comment: Please clarify your specific problem or provide additional details to highlight exactly what you need. As it's currently written, it's hard to tell exactly what you're asking.
Answer: In my opinion an Operations candidate (DevOps is a culture, not a role) should be capable to perform at least the following actions:

deploy postgres
backup postgres
restore postgres
run some psql commands like select and some innerjoins
knows what the effect on memory usage would be if a select * is issued
No manual labour, only automation. Deploy the postgres using a pipeline like gitlab
infrastructure as code
monitor it, disk usage, memory, cpu
the difference between a relational and non-relational database
see also this Q&A
there are tools like Flyway that are capable of applying version control to databases. This could facilitate to run it in a CI/CD.
Comment: if one considers devops a culture, then smooth change management is a key part of it. I wonder if you could update the answer with some reference to schema migration as part of a CI/CD pipeline?
Comment: @BruceBecker an example has been added
Answer: To add to 030's answer, and as a devops engineer who has had to do this a few times, learning how to set up replication and failover in an automated fashion is very important.
If you're learning, start by setting up replication by hand on some test servers
https://www.postgresql.org/docs/13/runtime-config-replication.html
Then craft a method for automating the configuration.  There are multiple ways to set up replication (they can run in parallel) and restoring a replicated database is pretty simple, but testing it out once and understanding how the file system is set up, what kinds of permissions users need to share data and what kinds of ACLs you need open between nodes to facilitate data transfer is very important.
You'd also want to craft a plan for what to do for promoting a new read/write master in case your primary node goes down.

Postgresql in DevOps skills


What is the Function of Pressurization Light on Exit Doors for Commercial Airliners?

Question: I am well aware that the average human is unable to open plug doors in flight due to pressurization of the cabin. I've noticed, however, a "cabin pressure" warning light in the window of exit doors, and specific instructions to not try to open the door when the light is on. Is there an actual danger of someone outside the aircraft being able to release something in or around the door while the cabin is under pressure, or is the light simply to indicate why they would be unable to move the handle?
Comment: Doors opening outwards does not mean they're non-plug. Both Boeing and Airbus use outward-opening plug doors. They only exception I can remember is the Boeing 767 which has inwards-opening plug doors for the main doors.
Comment: Many doors are not plug-type these days though. Airbus doors open outward.
Answer: It is there to prevent "violent door openings":

(figure 1b source)

In some abnormal cases, outflow valves can remain closed, when the
  aircraft is on the ground, causing the air pressure in the cabin to be
  higher than the ambient air pressure outside the aircraft (fig.1b). In
  this case, there is a risk that an aircraft door could violently open
  and injure the operator or damage the aircraft.

(fig 2 source)

The Residual Pressure Warning Light (fig.2), part of the residual pressure
  warning function, warns anyone who wants to open a door if the
  aircraft is pressurized. This device is installed on all Airbus
  aircraft except for some A300, A310 and A300-600 where it was offered
  as an option. On these aircraft not fitted with the warning light, a
  caution placard located on the door reminds the operator of the risk
  that residual pressure may cause violent door opening.

This brief from Airbus has a lot of good info on residual cabin pressure as well.

Not to be confused with the "Slide Armed" light.
Comment: Huh! Unlike the slide warning indicators, I always assumed the light was just for emergency access, and not something used at the gate. Makes sense! Especially helpful that there's a logic diagram for when it's active on that linked page, because I noticed that it never illuminated on normal flights so I assumed it only activated when doors were unlocked or something.
Comment: People don't realize that a "small" pressure difference can result in a very big force, over an large area like a door. The warning pressure level of 2.5mb gives a force of abut 5 pounds per square foot. The total force on a pressurized door could be 100 pounds or more, which is not something the door-opener wants to discover unexpectedly when the latch is released.
Comment: In 2000 there was an [incident](https://abcnews.go.com/US/story?id=94950&page=1) where a flight attendant opened a door before the plane fully depressurized and was sucked out. He fell to the ground and died from his injuries.
Answer: Is there a real danger? Yes, there is. A private jet pilot was killed when hit by a door at Kittilä, Finland, 2018.

The aircraft had arrived in Kittilä two days before and was about to
  take off for a positioning flight without passengers. During these two
  days the aircraft was parked outside. Considering the season, the
  weather was usual. On the day of the arrival it was lightly snowing
  and the temperature was -5 °C; on the day of the accident the
  temperature was -22 °C.
On the day of the arrival the captain completed the final cockpit
  procedures alone while the co-pilot was outside putting on the
  aircraft's external engine and sensor covers. At this point, the
  captain, apparently, closed the outflow valve because of the blowing
  snow.
On the day of the departure the co-pilot placed the aircrew's baggage
  into the rear baggage compartment and began to remove snow. The
  captain and the cabin attendant boarded the aircraft. The captain
  started the APU which generates bleed air for heating the cabin and
  electricity for aircraft systems. The captain selected APU bleed air
  to be ducted into the cabin. Following this, the captain went outside
  to assist the co-pilot in removing snow and frost.
A moment later the captain went back inside to fetch a pair of gloves.
  When he came back out, he closed the door. A little later the cabin
  assistant inside the cabin felt pressure in her chest and ears. She
  went into the cockpit and knocked on the window to get the attention
  of the pilots. The pilots discontinued the snow removal. The captain
  opened the door which, owing to the significant differential pressure
  between the cabin and the outside, blew open with excessive force,
  hitting the captain and knocking him to the ground. The pressure wave
  also knocked the co-pilot down.

Full investigation report:  https://www.turvallisuustutkinta.fi/en/index/tutkintaselostukset/ilmailuonnettomuuksientutkinta/tutkintaselostuksetvuosittain/2018/l2018-01ilma-aluksenpaallikonkuolemaanjohtanutonnettomuuskittilanlentoasemalla4.1.2018.html
Comment: "Is there a danger" is in relation to the ability of a human to open a plug door while under pressure. Accepted answer brings up residual pressure, which is the case where the plug door could be opened while "pressurized". While this is an example of violent door opening due to pressure while on the ground, it is unclear that this example addresses the question of plug doors.


View is returning two default results when no value in filter is being selected. Why?

Question: I have created a view to display node's title and added exposed filter for filtering content. When the view page is loaded it is returning two nodes , I do not know on what basis it is returning those two nodes.I want no result should be displayed until I select some value in filter.Please suggest ??
Comment: What are you trying to display in the views? terms, nodes... ?
Comment: Are you trying to display nodes of a particular type? If yes then how many nodes of that type has been created is it 2 or more?
Comment: Also, what do you mean by random? If you are asking for nodes without anything to narrow it down, you are getting all nodes, right? What's unexpected about that? Sorry, I would really like to help you, but I can't understand what you need. Please edit your question to show (roughly in order): 1) What you wanted to achieve? 2) what you did to achieve it? 3) how the effect differs from what you expected?
Comment: I have created a view to display node's title and added exposed filter for filtering content. When the view page is loaded it is returning two nodes , I do not know on what basis it is returning those two nodes.I want no result should be displayed until I select some value in filter.Please suggest ??
Comment: @Asthachauhan please edit your question. Data provided in comments will probably not be noticed by people who vote on your question (or vote to close it), and comments may get deleted without a notice in a cleanup process.
Answer: There is a views setting "Exposed form style", where you can select "Input required" if you don't want results to be displayed by default.
See the attached screenshots:

Then
Comment: Thanks for the easy solution ROBBY, it worked for me.Can you please tell me why those two random results were shown up?
Comment: No worries. Best to select an answer as being correct if there is one that is correct. It helps keep the list of "unanswered" questions on the site a little bit smaller and lets people see at a glance if a question they are interested in has an answer.
Answer: When you add a filter under Filter criteria, and select "Expose this filter to visitors, to allow them to change it", also check the "Required" checkbox. This will make the view not show any results until this filter has been submitted.
Update: this works generally (e.g. with the operator 'Contains' on a field), but not when the exposed filter is Content: Type. You can work around the error by checking "Limit list to selected items" and checking the content types that may be selected. However, now the view will initially be filtered on the first content type of the select list, instead of empty. See this Views issue.
Alternative solution
You can use the approach outlined here:

Choose Filter type to expose: Grouped filters
Deselect 'Optional'
Create a default option, e.g. a label 'Choose a content type', operator 'Is not one of' and select all available content types. This will return your empty view.
Create a label for each content type you want to expose and use 'Is one of' operator, with the corresponding content type checked.
Comment: Thanks for answering ARJAN but if I make filters required the view is not getting saved and throwing 'No valid values found on filter: Content: Type' error.
Comment: @Asthachauhan: yes, I can confirm that this is a problem with this particular filter. I've updated my answer; I'm not sure yet if there's another way.


Can I use Samsung fingerprint to authenticate users in my app?

Question: I was going through the Samsung SDK which supports "Pass" Fingerprint recognition as per the given link : http://developer.samsung.com/samsung-mobile#pass.
Can I use this Fingerprint recognition for authentication of our application?
Does any one have Samsung S5 and is this feature tested on this device our a third party app?
Answer:
First please be sure about the tag as it does not belong to
android.Its just samsung sdk going by the link you provided.
Second for the testing part of the fingerprint on Samsung S5 mobile
you could test it on the Emulator with the specified configuration of
the phone model due to unavailability of the phone right now.
Third for doing this you would need to integrate your eclipse with the samsung sdk
link. (OR)
If you just want to test the app in the Android adt emulator then you could simply download the Galaxy S5 emulator on developer.samsung.com and do the required test you want to do.
Answer: Yes, you can use it for authenticate your apps users, but they should use S5 for their authentications.
For more info see the YouTube video [Tutorial] Security With Pass SDK on the Samsung Developers channel


Google Earth API - geplugin.exe consumes all available memory

Question: Good afternoon to all. I searched up and down the web and did not find a solution to this rather big problem.
When I am running my app interfaced to Google Earth API, geplugin.exe comes up in the task manager and after a few user interactions with the Earth (zoom in/out, flyto a few points) all memory on their machine ends up being consumed by the geplugin. It unloads once they close my project but due to the business specs I can not keep on loading/unloading.
My guess would be that Earth caches the images and does not release them.
Anyone found a solution to this predicament?
I am running Google Earth v6.2 on Windows 7 with tons of memory.
Gratefully
Ig.
Answer: I have seen a memory leak in the google earth plugin.  It may not be the same, however, because it is not so drastic.  In my case, I was able to determine that the memory leak is related to 3-D terrain.  If I run my app with 3-D terrain enabled, there is a constant memory leak.  If I run it with 3-D terrain disabled, the memory footprint holds steady.
To disable 3-D terrain, you can use code like this.
ge.getLayerRoot().enableLayerById(ge.LAYER_TERRAIN, false);
My testing was done with version 22.214.171.12415 of the plugin.


Do blueberry bushes do well around pine stumps?

Question: We are purchasing property next to us that has a row of pine trees. I would like to cut a couple of the tree's down because it will be a sunny and acidic place for blueberry bushes. Can I leave the stumps and plant the berries in a circle around them? The stumps won't bother them if they are planted 3 or 4 feet away, will they?
Comment: It will be very difficult to grow blueberries if there are any rabbits in the county.
Answer: Yes, you can leave the stumps in the ground for food production as phoenix oyster mushrooms love them, and blueberries love pinetrees, so if you've ever seen pinetrees over blueberry bushes you've noticed they're very happy together.
Might I suggest that while the blueberry bushes are establishing themselves you leave the pine trees in the ground as they protect the bushes in their delicate time periods.


What files to give my Client for their Logo

Question: I took graphic design in school years ago, but have been out of the loop for quite some time. I recently created a vector logo for a friend for their business. I am wondering how to save the files so they have no background around the logo and so they can put on any form for print and rescale it to whatever size they wish. I also would like to give them one for their website. What would you recommend- and how to save it properly if you have specific instructions? I have saves a successful png for web use withough background... as well as an .ai file.
Comment: Also http://graphicdesign.stackexchange.com/q/55102/23061
Answer: First off, send a copy of the original vector should they need to alter the dimensions, otherwise save PNG-24's of each of the sizes below (PNG's for the transparency, but it does make images a raster format) . I would recommend you give a small logo size (maybe around 150px X 150px) for the site header, the size of a standard piece of A4 paper, and a size between those (you choose the size for that one). Also, optionally, you may want to include a huge blown up one for the sake of posters.
Worst comes to worst, just ask the client, better safe than sorry.


Increasing Enhancement Bonus on Specific Magic Weapons

Question: Is there a way to increase the enhancement bonus on specific magic weapons? For example if my character had a Mace of Terror (a +2 heavy mace with some extra magical abilities) would there be any way for it to be improved so that it would be a +3 heavy mace with the same magical capabilities?
Answer: Yes, according to the d20SRD:

A creator can add new magical abilities to a magic item with no
  restrictions. The cost to do this is the same as if the item was not
  magical. Thus, a +1 longsword can be made into a +2 vorpal longsword,
  with the cost to create it being equal to that of a +2 vorpal sword
  minus the cost of a +1 sword.

The Mace of Terror is a +2 heavy mace with a unique special ability that neither improves weapon accuracy or damage nor imitates any available non-unique weapon special ability (like returning or spell storing).
The cost to improve the enhancement bonus to +3 would be the same as for any +2 weapon: 10,000 gold.
Answer: It depends on your DM, but I'd rule yes.
Sometimes, determining how much of the cost of a specific weapon or piece of armor (shields included) comes from its unique properties is very hard, so some DMs just say that the weapon can't be crafted in any other variant than the one presented (with the added rationale that if they wanted you to be able to craft different versions of it, the developers would have provided the cost for the specific effect in the usual weapon enhancements table/chapter).
Anyway (proving negatives is a hard thing to do, so be aware that I might be wrong) I've never seen any manual snippet preventing people from upgrading those weapons/armors/shields.
A +2 weapon costs 8000 gp on top of its being perfect (300 gp) and the price of the heavy mace (12). The mace of terror costs 30240 gp more.
Now, 38240 is not a multiple of 2000×(any squared number) so I'd rule this property costing a flat 30240 gp. While I don't think such a property (3 times per day only, with a low will save) is worth that much, I'm going to use this value in my calculations and determine that the +3 equivalent costs 10000 gp more, for a grand total of 48552 gp.
Improving the mace to the next level would be done, as it is usual for upgrading magic weapons, by asking someone who has the appropriate weapon enchanting feat and access to someone casting the required magic weapon spell every day for 100 days.
Comment: Then, according to the rules as written, is the answer *No*?
Comment: @HeyICanChan I won't say so. The rules don't say if it is possible, but they don't say it's impossible either, while providing a formula to calculate an item's price and a way to upgrade weapons.
Comment: @Zachiel: Read the other answer to this question.  You may want to address the "Adding new Abilities" rule in your answer.


Where does the name "geometric theory" come from?

Question: In mathematical logic, where does the adjective "geometric" comes from, in terms like "geometric theories" and "geometric logic"?
These terms come up in fields like topos theory, e.g. in works such as the following:
The unification of Mathematics via Topos Theory
Answer: This answer is CW, so I don't gain reputation for someone else's work.
To quite Kevin Arlin's answer to the same question on math.stackexchange:

Geometric logic constitutes the logic, models of whose theories are preserved by geometric morphisms between topoi. Geometric morphisms are those appropriate to toposes viewed as generalized spaces, for instance, identifying the topos of sheaves on a topological space, or on a locale, with the space itself. Historically, toposes were first introduced by Grothendieck's school to model generalized algebro-geometric spaces, which explains why these morphisms are called geometric, rather than topological.
Answer: Negri and collaborators call "geometric" theories that can be axiomatized by FOL formulas of a special sort, namely universal closures of $A\to B$, where $A$ and $B$ do not contain $\to$ or $∀$, see e.g. Contraction-free sequent calculi for geometric
theories with an application to Barr's theorem. The terminology goes back to, at least, Constructivism in Mathematics by Troelstra and van Dalen (1988), where it is used in exercise 2.6.14. Such theories have  particularly nice proof theory, e.g. a classical proof  of a geometric implication in a geometric theory can be  transformed  into a constructive proof (Barr's theorem). This was originally proved in what they call "classical geometric theories" modeled in Grothendieck topoi, hence the name:

"Examples of geometric theories are given by Robinson arithmetic, the theory of
constructive plane affine geometry, the theory of ordered fields and of real closed
fields... In the last section we apply our method to a general result on geometric theories. The result states that if a geometric implication is provable classically
in a geometric theory, then it is provable intuitionistically.

This result is proved in topos theory by using a completeness theorem for geometric theories in
Grothendieck topoi and the construction of a suitable Boolean topos out of a Grothendieck topos.
By our method, the result reduces to a proof-theoretical triviality: A classical proof of a geometric implication in a geometric theory formulated as a sequent
system with rules is an intuitionistic proof already."

The name is doubly apt since a recent formalization of Euclidean geometry by Avigad, Dean and Mumma, that attempts (unlike Hilbert's) to mirror Euclid's proofs as closely as possible, is (nearly) geometric in the above sense, and their proof of its completeness uses Negri's results:

"Those geometric formulas with only a single disjunct in the consequent (i.e. geometric formulas in which $∨$ does not appear) are called regular. Note that, on our modeling, Euclid's propositions are almost of this latter form, the difference being that arbitrary literals (negated atomic formulas as well as atomic formulas) are allowed in the antecedent and consequent. Sara Negri [42], building on earlier joint work with Jan von Plato [43], has established a cut-elimination theorem for geometric theories that we can put to use in our completeness proof."
Answer: The geometry in geometric theories, as in topoi, comes from topology and hence also the name topos. They, that is the topoi, are seen as generalisation of a topology. This generalisation was by Grothendieck and generalises that of a topological covering which is, in his language, a sieve. And in this way we get elementary topoi, which was lawvere's axiomatisation of Grothendieck topoi, that is of sheaves on the poset of opens of underlying topological space, reverse ordered by inclusion.
Every topos has an internal language as generally seen in the underlying language of logic and it turns out that each topos has an intuitionistic logic.
Generally, in mathematics, geometry refers to the metric as this is used to measure distances and angles; here, it refers to the aspect of continuity of geometry and hence the geometric moniker.
Given that each topos has a logic, this is why these logics are termed geometric logic.


get cat id is not working from custom taxonomy

Question: I have a custom taxonomy "city". I am having a hard time to get cat id. the number.
It's also custom post type "job"
This works only for default category under the default post.
  $provinceID = get_cat_ID($cityname);
  echo "
bb=".$provinceID."
";

I have found this one but it's not also working as well.
the function name was get_cat_ID and it caused an error. so I have changed name.
  function get_cat_ID11( $cat_name='$cityname' ) {
$cat = get_term_by( 'name', $cat_name, 'category' );
if ( $cat )
    return $cat->term_id;
return 0;
  }

  echo get_cat_ID11;

How can I get the cat id from custom taxonomy , custom post type?
Answer: I have just found the solution.
I just miss to put a taxonomy name.
     $cat = get_term_by( 'name', $cat_name, 'city' );

this works fine!
Thanks,


Is RDSEED a true RNG?

Question: Is Intel's RDSEED a true random number generator?
Comment: I removed your question about the software implementation. Implementation questions should be asked on Stackoverflow.
Answer: Yes, RDSEED is a true random number generator.
From Wikipedia:

The entropy source for the RDSEED instruction runs asynchronously on a self-timed circuit and uses thermal noise within the silicon to output a random stream of bits at the rate of 3 GHz [...].

RDSEED is however used as a seed for (software implemented) PRNGs of arbitrary width.
Comment: I would say that we need to be pretty careful with citing Wikipedia. Unless the text is backed up by credible sources, we should probably tread with caution. Come to think of it, some of what we read, especially on sensitive topics such as cryptography, may be misinformation.
Comment: @Patriot: A better source is https://www.electronicdesign.com/resources/article/21796238/understanding-intels-ivy-bridge-random-number-generator - it discusses the metastable flip-flop which settles due to thermal noise.  The article also discusses how the entropy is "conditioned" or "whitened" by feeding it through AES.  That article is by Michael Hamburg, one of the authors of a review of the internals, and the references it cites include "D. J. Johnston, "Mircoarchitecture Specification (MAS) for PP-DRNG," Intel Corporation (unpublished), V1.4, 2009." - David Johnston has posted on SO.
Answer: Intel says it is a true RNG, and so do people who've looked at the design details Intel shared with them.
The possibility of it not being a true RNG are basically limited to NSA interference and a big coverup with Intel's knowledge (perhaps in the conditioning logic), or some kind of covert modification of the design that actually gets laid down in silicon.  Perhaps one that makes the rdrand instruction return data from a pure CSPRNG seeded somehow, not using the true randomness that the RNG hardware has prepared.
Both of these are unlikely but impossible to rule out.  It's been a decade since IvB was released, and nobody involved with the design has leaked any details about NSA interference or backdoors, or other shenanigans, and nobody's found anything reverse-engineering.
Other vendors (including AMD) have implemented rdrand in their CPUs, too, presumably with an independent design.  (AMD infamously had a bug with their rdrand in Ryzen 3000, where it always returned 0xFFFFFFFF, eventually fixed with a microcode update.)
It's impossible to prove that randomness is true, and not from a sufficiently-good CSPRNG. And the transistors are so small that it's not particularly doable to actually reverse-engineer a real chip in the wild to see if it actually works the way Intel and others say they work.
It makes sense to mix it with other entropy sources if you have any available, like Linux does to implement /dev/random, out of an abundance of caution if nothing else.  And because you need a fallback in case the CPU has a non-functioning rdrand; the instruction documentation allows it to return failure indefinitely, like if it fails its self-tests.
But there are entropy-mixing algorithms that don't lose (much) existing entropy if the new source being mixed in is actually not valuable.  So it usually makes sense to use rdrand as one source of entropy.  Especially for embedded systems, there often aren't any other good sources of entropy in early boot, so an HWRNG helps a lot, much better than nothing.

But with that out of the way, it's highly likely that it does work the way it's claimed to.
Intel and people who have reviewed the design have published some stuff about the internals.  Understanding Intel's Ivy Bridge Random Number Generator  is one such article, by Michael Hamburg of Cryptography Research, inc., one of the authors of an independent study of the design that Intel contracted out.
The true-randomness source is a metastable flip-flop (RS-NOR latch) which settles due to thermal noise.
This source of a stream of 0 and 1 bits is then conditioned, aka whitened, by feeding it through AES in counter mode.

Finally, the seed is passed to a pseudorandom generator, which generates the RNG's final output. Under normal load, the generator reseeds every time it produces an output, so its output should be almost completely statistically random. Under very heavy load, it can generate multiple blocks of output between reseeds. In this case, the generator has 256 bits of state, and finding patterns in it is as hard as breaking 128-bit AES.

There's a buffer that rdrand instructions pull from; in IvB there weren't enough cores to ever exhaust it and make it set CF=0 (according to David Johnston's answer on Stack Overflow; and he should know since he designed the hardware buffer logic and wrote librdrand), but later CPUs can exhaust the buffer.
After microcode updates to fix possible MDS vulnerabilities, rdrand is vastly slower on some Intel CPUs.  RdRand Performance As Bad As ~3% Original Speed With CrossTalk/SRBDS Mitigation.  See also updated timing numbers on https://uops.info/, like one per 3554 cycles on Skylake.  See the Performance / internals of rdrand / rdseed section at the bottom of an SO answer I wrote.  Performance of using it, and practicalities like whether to make your retry loop infinite.
Comment: @PaulUszak: The entire first half of my answer is dedicated to making that point.  Keep reading beyond the TL:DR, which I intentionally phrased as "Intel says".
Comment: Re. 1st sentence: you're relying on hearsay since modern CPUs can't be physically audited. Public design does not guarantee private implementation.
Answer: No one knows, so we can't say because of the two obstacles of non auditability and computational indistinguishably. But it's not looking good at all.
Since the device is completely unverifiable, it could do anything.  All we know for certain is that it is impossible to mathematically verify true randomness.  Computational indistinguishably means that the output could simply be any decent $ \operatorname{E}_{k \; \oplus \; cpuid} (ctr) $  like CSPRNG. Intel state that it's AES-CBC-MAC throughout anyway.
Wikipedia is not the oracle of all truth, and has to be ignored in this context.  The primary verification of the device is ANALYSIS OF INTEL'S IVY BRIDGE DIGITAL RANDOM NUMBER GENERATOR. That was followed up with an academic report, A Provable-Security Analysis of Intel's Secure Key RNG.  Unfortunately for users, both reports are based on a raw entropy rate of ~0.5 bits/bit. And to be a gold standard TRNG, (entropy out) < (entropy in). But it says in those reports:-

"We did not have access to Ivy Bridge parts, so Intel provided us with testing data from
  pre-production chips. These chips allow access to the raw ES output, a capability which
  is disabled in production chips. "

The whole analysis is built on sand. Many factors create reasons for suspicion:-

It is not in the interest of the US government/NSA/security community to produce fast secure random number generators for public use. Cui bono?
The NSA has form on this, with many examples publicly available.
All public analysis of the chip is based on unverified data samples supplied by Intel themselves. Is ~0.5 bits/bit real?
The primary analysis of RDSEED was paid for by Intel which is a huge conflict of interest, tantamount to marking your own homework. From that report's front page  - "This report was prepared by Cryptography Research, Inc. (CRI) under contract to Intel Corporation".
The entropy source operates at a suspiciously high 3GHz.  Academic laboratory TRNG's have only recently attained this rate using optical means (green line below). If true, I would expect huge correlation at this sample rate. Injecting 1% entropy into a CSPRNG stream does not make a TRNG.
The pink marked devices show how easy/common it is to over-hype your TRNG.  These marked devices have exceeded a very conservative engineering limit (Shannon-Hartley) beyond which it is mathematically impossible to extract any more entropy.  Some others appear to be suspiciously right on the limit.  From Recommendations and illustrations for the evaluation of photonic random number generators.
The entropy source is an atypical circuit not replicated in the hacker community, and the only detailed analysis is by Intel themselves and unpublished. (C. E. Dike, "3 Gbps Binary RNG Entropy Source," Intel Corporation (unpublished),
2011.)
The typical completely in-silicon TRNG is synthesised via multiple ring oscillators.  Inverters are easy to burn in their hundreds.  There are numerous examples at all levels of academia and commerce. Intel chose not to for some reason, preferring to go analogue on an otherwise entirely digital die.
There is no raw entropy source available for inspection, and even if there was, the level of integration means that we can't verify that the source is actually used.
*nix developers do not trust it.

But the best for last. Even Intel could not convince it's own agent that it's a good TRNG:-

Under heavy load, it should
  provide security equivalent to 128-bit AES, even against an attacker who can see some of
  its outputs and, after a good reseed, force the ES to output nonrandom, known values.

-Cryptography Research, Inc. (CRI).
If you accept that an effective TRNG has information theoretic security via the entropy input/output ratio, Intel's isn't.  Given all the evidence against, and who benefits if it isn't, I have to conclude it's a CSPRNG (at best), and not a TRNG. Most of the *nix community agrees with me.
Comment: I'd consider that "it's too uncertain to be *used* as a TRNG" a better phrase. It could very well be a TRNG (and personally I expect it to be so, if just because of the fallout produced if it isn't). However I agree that it certainly hasn't been proven to be one beyond reasonable doubt. In the end though it is a TRNG - or an RNG based on a TRNG - or it isn't, and that doesn't depend on opinion.
Comment: Although there are some good points in this answer, the last paragraph is nonsense. A TRNG has no inputs, and the RDSEED chip has no inputs. It's most definitely not a CSPRNG: there is an entropy source, and the question here is the quality of this entropy source. The cited sentence from CRI _does_ say that it's a good TRNG, providing sufficient entropy against a reasonably powerful attacker. As you note this is a biased source, but it doesn't at all say what you claim it says.
Comment: @flarn2006 They are under US jurisdiction which includes a shed load of security legislation, esp. > 9/11. Just as I am (even in the UK) subject to the US Cloud Act via bi-lateral international treaty with the US. Sigh. Plus they are heavily contracted to the US government and money talks.
Comment: @Gilles Great comment!  Why do you believe that my direct quotation isn't? The I/O ratio relates to the Shannon-Hartley  criteria across the extractor.  This is where true magic can exist. And we know nothing of the source and/or biases as it can't be audited. I'd have thought that you'd have known the construct's dodgy from your Unix persona. All the development influencers have abandoned RDThing. It's pretty clear they're right to do so.
Comment: "It is not in the interest of the US government/NSA/security community to produce fast secure random number generators for public use." Intel isn't part of the government, so why would they care?

Is RDSEED a true RNG?