Results 1  10
of
21
Supporting Timing Analysis by Automatic Bounding of Loop Iterations
 Journal of RealTime Systems
, 2000
"... . Static timing analyzers, which are used to analyze realtime systems, need to know the minimum and maximum number of iterations associated with each loop in a realtime program so accurate timing predictions can be obtained. This paper describes three complementary methods to support timing analy ..."
Abstract

Cited by 45 (7 self)
 Add to MetaCart
. Static timing analyzers, which are used to analyze realtime systems, need to know the minimum and maximum number of iterations associated with each loop in a realtime program so accurate timing predictions can be obtained. This paper describes three complementary methods to support timing analysis by bounding the number of loop iterations. First, an algorithm is presented that determines the minimum and maximum number of iterations of loops with multiple exits. Even when the number of iterations cannot be exactly determined, it is desirable to know the lower and upper iteration bounds. Second, when the number of iterations is dependent on unknown values of variables, the user is asked to provide bounds for these variables. These bounds are used to determine the minimum and maximum number of iterations. Specifying the values of variables is less error prone than specifying the number of loop iterations directly. Finally, a method is given to tightly predict the execution time of in...
Performance Improvement Through Overhead Analysis: A Case Study in Molecular Dynamics
 in Molecular Dynamics, Proc. 11 th ACM International Conference on Supercomputing, ACM
, 1997
"... A method is presented for incremental development of high performance parallel programs, using an application from molecular dynamics as a case study. The method uses the technique of overhead analysis, which aims to explain experimental observations using models of execution behaviour, as a means o ..."
Abstract

Cited by 11 (3 self)
 Add to MetaCart
(Show Context)
A method is presented for incremental development of high performance parallel programs, using an application from molecular dynamics as a case study. The method uses the technique of overhead analysis, which aims to explain experimental observations using models of execution behaviour, as a means of determining successive steps in program development. The case study illustrates how this technique can be applied to the complexities of realworld parallel computations. 1 Introduction Parallel computers have so far failed to fulfil their promise of providing cheap high performance computing. In part, this is due to the high cost of software development required to find an acceptable implementation of an application which runs efficiently on a given parallel system: this has been termed the `best' implementation problem [4]. Execution time is, in general, unpredictable and, often, decisions made early in the development process have profound effects on the ultimate performance of an ap...
Algorithms for weighted counting over parametric polytopes: A survey and a practical comparison
, 2008
"... The polytope model is widely used in compiler analysis for representing a certain class of programs. Many counting problems that occur in the analysis of such programs can be solved by counting the number of integer points in a parametric polytope. In other counting problems, polynomial weights ar ..."
Abstract

Cited by 9 (3 self)
 Add to MetaCart
(Show Context)
The polytope model is widely used in compiler analysis for representing a certain class of programs. Many counting problems that occur in the analysis of such programs can be solved by counting the number of integer points in a parametric polytope. In other counting problems, polynomial weights are assigned to the integer points of a parametric polytope and the objective is to find the sum of these weights over all integer points. This paper briefly surveys a number of algorithms for solving such problems, extending them where needed and evaluating them on a set of realistic and constructed examples from compiler analysis and beyond. The paper also serves to document some of the algorithms implemented in the freely available barvinok library.
Compiletime minimisation of load imbalance in loop nests
 In Proceedings of the International Conference on Supercomputing
, 1997
"... Parallelising compilers typically need some performance estimation capability in order to evaluate the tradeoffs between different transformations. Such a capability requires sophisticated techniques for analysing the program and providing quantitative estimates to the compiler’s internal cost m ..."
Abstract

Cited by 8 (2 self)
 Add to MetaCart
Parallelising compilers typically need some performance estimation capability in order to evaluate the tradeoffs between different transformations. Such a capability requires sophisticated techniques for analysing the program and providing quantitative estimates to the compiler’s internal cost model. Making use of techniques for symbolic evaluation of the number of iterations in a loop, this paper describes a novel compiletime scheme for partitioning loop nests in such a way that load imbalance is minimised. The scheme is based on a property of the class of canonical loop nests, namely that, upon partitioning into essentially equalsized partitions along the index of the outermost loop, these can be combined in such a way as to achieve a balanced distribution of the computational load in the loop nest asawhole. A technique for handling noncanonical loop nests is
Symbolic Evaluation of Sums for Parallelising Compilers
 In IMACS World Congress on Scientific Computation, Modelling and Applied Mathematics. Wissenshaft & Technik
, 1997
"... The evaluation of sums over polynomials when symbolic, i.e., unknown, variables are involved in the bounds of the sums is considered. Such sums typically occur when analysing, in computer programs, the properties of loops which can be executed in parallel. Existing packages for symbolic mathematical ..."
Abstract

Cited by 7 (0 self)
 Add to MetaCart
The evaluation of sums over polynomials when symbolic, i.e., unknown, variables are involved in the bounds of the sums is considered. Such sums typically occur when analysing, in computer programs, the properties of loops which can be executed in parallel. Existing packages for symbolic mathematical computations are not capable of handling these sums properly. The problems which may arise are identified and an algorithm to overcome them is presented.
Parametric timing estimation with Newton–Gregory formulae
, 2006
"... This paper presents a novel method for parametric worstcase execution time (WCET) estimation of loops. The method determines a parametric bound on the iteration space size of loops with both affine and nonaffine loop bounds in an efficient manner using a formulation based on Newton–Gregory interpol ..."
Abstract

Cited by 5 (0 self)
 Add to MetaCart
(Show Context)
This paper presents a novel method for parametric worstcase execution time (WCET) estimation of loops. The method determines a parametric bound on the iteration space size of loops with both affine and nonaffine loop bounds in an efficient manner using a formulation based on Newton–Gregory interpolating polynomials. Parametric WCET formulae are used to support dynamic scheduling decisions at runtime, where the WCET of a scheduled task might not be known statically. To determine worstcase execution time estimates of scientific and multimedia codes, which spent most of the execution time on executing loop iterations, efficient and accurate symbolic loop WCET estimation methods must be capable of analyzing loops with symbolic bounds, nonrectangular loops, zerotrip loops, loops with multiple critical paths, and loops with nonunit strides.
Polynomial approximations in the polytope model: Bringing the power of quasipolynomials to the masses
 In ODES6: 6th Workshop on Optimizations for DSP and Embedded Systems
, 2008
"... This paper addresses one issue in the polyhedral model of loop nests that limits its practical applicability. We present methods for avoiding the use of quasipolynomials when enumerating integer points in polyhedra, by computing polynomial approximations of the quasipolynomials and also polynomial ..."
Abstract

Cited by 4 (4 self)
 Add to MetaCart
(Show Context)
This paper addresses one issue in the polyhedral model of loop nests that limits its practical applicability. We present methods for avoiding the use of quasipolynomials when enumerating integer points in polyhedra, by computing polynomial approximations of the quasipolynomials and also polynomial upper and lower bounds of the quasipolynomial. We propose two methods and different variants thereof. An evaluation on a set of systems of linear equalities generated by several compiler analyses shows that the accuracy of our more advanced method is similar to or better than the accuracy of existing techniques, while the computation is faster on difficult problems. 1.
Automatic Utilization of Constraints for Timing Analysis
 Florida State University
, 1999
"... Users of realtime systems are not only interested in obtaining correct computations from their programs, but timely responses as well. Responses that are given past a deadline is not acceptable. Arealtime system is often comprised of a set of tasks that are statically scheduled. Therefore, it is n ..."
Abstract

Cited by 4 (1 self)
 Add to MetaCart
(Show Context)
Users of realtime systems are not only interested in obtaining correct computations from their programs, but timely responses as well. Responses that are given past a deadline is not acceptable. Arealtime system is often comprised of a set of tasks that are statically scheduled. Therefore, it is necessary to determine a program’s execution
A CompileTime Partitioning Strategy for NonRectangular Loop Nests
 In Proceedings of the 11th International Parallel Processing Symposium (Geneva
, 1997
"... This paper presents a compiletime scheme for partitioning nonrectangular loop nests which consist of inner loops whose bounds depend on the index of the outermost, parallel loop. The minimisation of load imbalance, on the basis of symbolic cost estimates, is considered the main objective; however, ..."
Abstract

Cited by 3 (2 self)
 Add to MetaCart
(Show Context)
This paper presents a compiletime scheme for partitioning nonrectangular loop nests which consist of inner loops whose bounds depend on the index of the outermost, parallel loop. The minimisation of load imbalance, on the basis of symbolic cost estimates, is considered the main objective; however, options which may increase other sources of overhead are avoided. Experimental results on a virtual shared memory computer are also presented. 1.
A Geometric Approach for Partitioning NDimensional NonRectangular Iteration Spaces
"... Abstract. Parallel loops account for the greatest percentage of program parallelism. The degree to which parallelism can be exploited and the amount of overhead involved during parallel execution of a nested loop directly depend on partitioning, i.e., the way the different iterations of a parallel l ..."
Abstract

Cited by 2 (0 self)
 Add to MetaCart
(Show Context)
Abstract. Parallel loops account for the greatest percentage of program parallelism. The degree to which parallelism can be exploited and the amount of overhead involved during parallel execution of a nested loop directly depend on partitioning, i.e., the way the different iterations of a parallel loop are distributed across different processors. Thus, partitioning of parallel loops is of key importance for high performance and efficient use of multiprocessor systems. Although a significant amount of work has been done in partitioning and scheduling of rectangular iteration spaces, the problem of partitioning of nonrectangular iteration spaces e.g. triangular, trapezoidal iteration spaces has not been given enough attention so far. In this paper, we present a geometric approach for partitioning Ndimensional nonrectangular iteration spaces for optimizing performance on parallel processor systems. Speedup measurements for kernels (loop nests) of linear algebra packages are presented. 1