9419059
TLDFS: A Distributed File System based on the Layered Structure
This paper presents a novel distributed file system TLDFS, which consists of two layers. One is the block device layer, which makes the distributed file system manage the consistency of data easily by choosing an appropriate granularity of lock. We implement the distributed interfaces and the new data organization at the block level, which is different from most distributed file systems. The other is the file system layer that consists of three parts: interconnecting module, locking module and distributed file system module. Our prototype system proves the feasibility of the two-layered structure and the experiments show several advantages of TLDFS.
14387828
Escape analysis for synchronization removal
In this paper we introduce our escape analysis framework for Java, which is a kind of flow-insensitive, inter-procedural, and context-sensitive data flow analysis. And we present an efficient static intra-procedural algorithm for inferring the set of types that can occur at runtime for each object. With intra-procedural type information, virtual method resolution, callee-stub inline, exception analysis, and thread allocation site analysis are implemented. Virtual method resolution and callee-stub inline effectively reduce the call graph and SCC (strongly connected components). In exception analysis, we present a more precise analysis algorithm, especially in the inter-procedural exception in SCC.Our escape analysis can be applied to the whole Java program and Java libraries to identify unnecessary synchronization in Java and remove them. We have developed an implementation on Intel's Open Runtime Platform. For our benchmarks, 7.3% to 99% (with an average of 54%) of synchronization operations are eliminated.
15857630
Eliminating Redundant Communication of Code Generation for Distributed Memory Machines
How to eliminate redundant communications is a key issue in developing parallelizing compilers for distributed memory machines. An important way to improve the performance of the code generated by parallelizing compiler in distributed memory systems is to eliminate as much communications as possible. This paper investigates algorithms for generating communications code from previously published work and modifies them to eliminate redundant communications. Based on the mathematical model of symbolic coefficient linear inequalities the revisited formal specification of communications sets are presented and the corresponding improved algorithms are given. Experimental results indicate that the new algorithms can reduce communication messages and improve the performance of parallelized code significantly.
29918508
Round-Robin with VirtualClock Scheduling Algorithm in Multiservice Packet Networks
In this paper, we present a scheduler that incorporates round robin service within a VirtualClock discipline. Time-stamp based scheduling algorithms attain a low local delay bound and performance guarantee, but are computationally complex. On the other hand, round robin schemes are simple to implement and have computational complexity of O(1) but they are well known for their output burstiness and short-term unfairness. In order to overcome this problem, we combine round robin with VirtualClock in an algorithm we call VCRR. VCRR possesses better fairness than simple round robin, low jitter and a good scheduling delay bound. At the same time, VCRR preserves the O(1) time complexity of round robin. Simulation experiments show VCRR's efficiency in terms of delay performance, jitter and fairness..
15438049
DECF: A Coarse-Grained Data-Parallel Programming Framework for Seismic Processing
In this paper, we present a distributed execution control framework (DECF) for seismic processing. The DECF framework employs a coarse-grained data-parallel execution model within a cluster environment and achieves high throughput. The DECF schedules processing modules written as sequential programs to run simultaneously on multiple computers, or multiple CPU cores. The DECF hides the messy details of scheduling the use of computers and their CPUs, recovering from communication or computer failures, and transporting data between processing modules.We also introduce a parallel implementation of 3D pre-stack kirchhoff time migration algorithm using MPI and share the practical lessons learned from the process of designing, implementing, and maintaining it, which are of great help to the future work of the DECF.
41699961
Automated Detection of Code Vulnerabilities Based on Program Analysis and Model Checking
Ensuring the correctness and reliability of software systems is one of the main problems in software development. Model checking, a static analysis method, is preponderant in improving the precision of vulnerabilities detection. However, when applied to buffer overflow and other bugs, it is hard to automatically construct the model for detecting the vulnerabilities. To address this problem we propose an approach that combines constraint based analysis and model checking together. We trace the memory size of buffer-related variables and instrument the code with corresponding constraint assertions before the potential vulnerable points by constraint based analysis. Then the problem of detecting vulnerabilities is converted into the problem of detecting vulnerabilities to verifying the reach ability of these assertions by model checking. In order to reduce the cost of model checking, program slicing is introduced to reduce the code size. CodeAuditor is a prototype implementation of our approach. With CodeAuditor, several yet unreported vulnerabilities are discovered in several open source software, and the performance is shown to be improved significantly with the help of program slicing.
16913320
Continuity Properties of Equilibria in Some Fisher and Arrow-Debreu Market Models
Following up on the work of Megiddo and Vazirani [10], who determined continuity properties of equilibrium prices and allocations for perhaps the simplest market model, Fisher's linear case, we do the same for: 
 
 
Fisher's model with piecewise-linear, concave utilities 
Fisher's model with spending constraint utilities 
Arrow-Debreu's model with linear utilities 
Eisenberg-Gale markets.
42393300
Synchronization between Two Different Hyperchaotic Dynamical Systems Using Nonlinear Control
This paper presents synchronization between two different hyperchaotic systems by nonlinear control laws. First, we introduced hyperchaotic Rossler system and hyperchaotic Chen system, and then synchronization problem between hyperchaotic Rossler system and hyperchaotic Chen system has been investigated. We consider the hyperchaotic Rossler system as the drive system and hyperchaotic Chen system as the response system. Last, Numerical simulations are shown to verify the results.
5460989
End-To-End Worst-Case Response Time Analysis for Hard Real-Time Distributed Systems
The verification of end-to-end response time for distributed hard real-time systems is quite necessary for safety-critical applications. Although current time analysis techniques can precisely analyze the response time, the performance is not quite satisfying, especially for large size distributed systems. This paper presents a novel end-to-end worst-case response time analysis approach for hard real-time distributed systems. This technique is based on the critical instant analysis and the canonical form transformation. It extends the traditional holistic analysis technique by exploiting the precedence relations between tasks on both different processors and the same processor. Simulation results have shown that this algorithm can achieve accurate results and offers good performance for systems with wide range of CPU utilizations and task set size, and therefore is applicable to schedulability analysis of complex distributed systems.
14541123
An evolutionary algorithm with population immunity and its application on autonomous robot control
The natural immune system is an important resource full of inspirations for the theory researchers and the engineering developers to design some powerful information processing methods aiming at difficult problems. Based on this consideration, a novel optimal-searching algorithm, the immune mechanism based evolutionary algorithm - IMEA, is proposed for the purpose of finding an optimal/quasi-optimal solution in a multi-dimensional space. Different from the ordinary evolutionary algorithms, on one hand, due to the long-term memory, IMEA has a better capability of learning from its experience, and on the other hand, with the clonal selection, it is able to keep from the premature convergence of population. With the simulation on autonomous robot control, it is proved that IMEA is good at the task of adaptive adjustment (offline), and it can improve the robot's capability of reinforcement learning, so as to make itself able to sense its surrounding dynamic environment.
12587822
Clustering Research Based on Density Gradient
Cluster analysis, intending to help users understand the natural grouping or structure in a data set, has received a lot of attention in the last few years. Aimed to solve difficult problems in clustering with irregularly distributed data set, a new clustering algorithm based on density gradient is provided. With analysis of density of each point and its neighbors, the algorithm searches points with the maximum density and takes them as centers of original clusters. Then it combines some little clusters into larger clusters according to the distribution of boundary points between neighbor clusters. Experimental results show that the new algorithm has better performance than DBSCAN.