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[Bug gcov-profile/47618] Collecting multiple profiles and using all for PGO
- From: "roland at rschulz dot eu" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: Wed, 25 Jul 2012 00:50:30 +0000
- Subject: [Bug gcov-profile/47618] Collecting multiple profiles and using all for PGO
- Auto-submitted: auto-generated
- References: <bug-47618-4@http.gcc.gnu.org/bugzilla/>
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47618
--- Comment #11 from Roland Schulz <roland at rschulz dot eu> 2012-07-25 00:50:30 UTC ---
Steven wrote that they are not merged but that race conditions occur. That is
also what I observed. To clarify: Message Passing Interface (MPI) is a
parallelization method which executes the same binary multiple times in
parallel (with support for messages for communication). Allowing to merge the
output into one file at runtime would require file-locking (often over network
file-systems) and would not scale because MPI applications are often used with
more than >10000 (or even >1M) parallel processes simultaneous.