A company currently pays a fixed sum for the use of a particular licensed software package.   In determining if it has a good deal it decides to calculate its maximum use of the software from its license management log file.

Assume the software's licensing daemon faithfully records a checkout event when a copy of the software starts and a checkin event when the software finishes to its log file.

An example of checkout and checkin events are:

 License OUT @ 2008/10/03_23:51:05 for job 4974
 ...
 License IN  @ 2008/10/04_00:18:22 for job 4974



Task

Save the 10,000 line log file from    here   into a local file, then write a program to scan the file extracting both the maximum licenses that were out at any time, and the time(s) at which this occurs.

Mirror of log file available as a zip here (offsite mirror).




 
# Read in data, discard useless bits
dfr <- read.table("mlijobs.txt")
dfr <- dfr[,c(2,4)]
# Find most concurrent licences, and when
n.checked.out <- cumsum(ifelse(dfr$V2=="OUT", 1, -1))
times <- strptime(dfr$V4, "%Y/%m/%d_%H:%M:%S")
most.checked.out <- max(n.checked.out)
when.most.checked.out <- times[which(n.checked.out==most.checked.out)]
# As a bonus, plot license use
plot(times, n.checked.out, type="s")
 