CS 591x Profiling Parallel Programs Using 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 performance In 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 suites gprof – 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 execution Must add profile data collection calls to your code profiling calls can effect performance but relative performance should be consistent Optimization can impact profiling

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

pgprof … then execute as normal produces profile data file(s)….. pgprof.out … … then run pgprof [pgprof.out]

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