Gprof

On Lawrencium, gprof is available as part of the standard GNU binutils and does not require loading a module. Below is a concise guide on how to use it to profile your C,C++, or Fortran applications; please consult with gprof documentation for further details.

1. Compile with Profiling Enabled

   To use gprof, compile and link your code with -pg flag. This tells the compiler to insert code to collect profiling information.

   CC++Fortran

   gcc -pg -o program program.c
   

   g++ -pg -o program program.cpp
   

   gfortran -pg -o program program.f90
   

2. Run the Program

   Execute the program normally. You should run this within a slurm job or an interactive session (not on a login node).

   When the program finishes execution, it will generate a file named gmon.out in the current working directory. For MPI applications, set the environment variable:

   export GMON_OUT_PREFIX=gmon.out
   

   such that each MPI rank will produce a unique file gmon.out.pid where pid is the process ID of the MPI process.

3. Generate the Profile Report

   After the run completes and gmon.out is created, use gprof to analyze the data.

   gprof program gmon.out > analysis.txt
   

   The output file called analysis.txt in the example above contains a flat profile and a call graph.