Taking advantage of GCCbs profilearcs optimization

connclark

I was wondering if anybody has played around with using GCC's profile arcs optimization. I figured I would mention it since making OpenFOAM just a little faster would have big payoffs for serious computations.

how you use it.

1) compile your app as normal but add the flag -fprofile-generate

2) run your app on a _good_ sample case. when the app exits it will put a <source>.gcda file in the directory where the source is located for your app.

3) recompile your app. This time remove the -fprofile-generate flag and add the -fprofile-use flag. Gcc will now use the profile data in the gcda file to optimize your code.

4) Use your app as you normally would and enjoy the fact it runs faster now


I haven't tried it on OpenFoam yet, but on other apps I have found a speed increase of 2 to 13%.