Hi ! I'm David Bruant, I'm french, so sorry if my english is not perfect. Here is my problem On the manual chap 3 page 99 (111 of the pdf document), there are explanations about -fbranch-probabilities : "After running a program compiled with ‘-fprofile-arcs’ (see Section 3.9 [Options for Debugging Your Program or gcc], page 63), you can compile it a second time using ‘-fbranch-probabilities’, to improve optimizations based on the number of times each branch was taken. When the program compiled with ‘-fprofile-arcs’ exits it saves arc execution counts to a file called ‘sourcename.gcda’ for each source file. The information in this data file is very dependent on the structure of the generated code, so you must use the same source code and the same optimization options for both compilations." And I've got a problem with the "When the program compiled with ‘-fprofile-arcs’ exits" because I am running a backtrack algorithm which is not going to exit before the end of the universe, but I would be interested to have a (very) good solution (or at least the beginning of one) of my problem before my death, that's why I would like to improve its speed thanks to -profile-arcs and -fbranch-probabilities. I have had an idea which would be to force the end of the algorithm thanks to a variable which would end it after 2 hours (for example). This way, -fprofile-arcs would have a wide enough sample to improve with -fbranch-probabilities, but the "you must use the same source code" frightens me because if I add a variable to measure time, it's obviously not the same source code. So, could anyone tell me more about the restrictions of -fprofile-arcs and if my idea is a good one ? Thanks David Bruant
