CS 591x

Profiling Parallel ProgramsUsing the Portland Group Profiler

Performance and Profiling

Since parallel programming is all about performance…… we may want to study our programs in terms of their performance…and look for ways to enhance performanceIn a production application a small change may make a big difference

Performance and Profiling

We could … Try running our programs on different

machines (Xeon vs. Pentium) Tweak our code and rerun rescale our application to use more

processors

MPI_Wtime()

Profiling

We may want to look at our code… and see how it is performing internally… how the various pieces are performing during execution

Profiling

A Profiler … A tool to examine the performance of

a program while it is executing Can examine the performance at

function/routine level… … or at line level

Profiler

Profilers … can report the number of calls to a

function or line can report the percentage of call to a

function or line often have some graphics capability –

bar graphs

Profiler

Profilers are often part of development tool suitesgprof – GNU’s profiler part of the gcc suite free – part of most Linux distributions gcc –pg myprog.c –o myprog

pgprof – Portland Group Profiler part of the Portland Group Cluster

Development kit

pgprof

Analyzes/reports performance data based on program executionMust add profile data collection calls to your codeprofiling calls can effect performance but relative performance should be consistentOptimization can impact profiling

pgprof

Must compile/link code with -Mprof= option -Mprof=func -Mprof=lines -Mprof=mpi -Mprof=lines,mpi

pgprof

… then execute as normalproduces profile data file(s)….. pgprof.out …… then runpgprof [pgprof.out]

For more information…

http://www.pgroup.com/doc/pgitools.pdf