Author: Robert Hyatt
Date: 09:56:44 08/07/99
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On August 07, 1999 at 08:13:33, Vincent Diepeveen wrote: >installed gcc 2.95 a few days ago. >didn't speedup diep at all, whatever option i tried >or used. > >HOWEVER, >where i recently reported about all problems diep had >with linux, now a different story. > >All those problems DIEP had with linux have dissappeared. >DIEP runs stable under linux, no forfeits at a dual machine >sincethen at the icc server. > >Seems gcc 2.95 is a big step forward for my program! > >Greetings, >Vincent I would be concerned, if that fixed (or hid) your bugs. I am using this same compiler, and find that it is almost identical to my favorite version of pgcc. Very little difference in execution speed. And there have been no serious parallel programming bugs exposed in the older gcc/egcs compilers. We have all sorts of parallel programming going on here using gcc under linux, and in over 2 years, we have _never_ found a bug in the code produced by the compiler. However, if you have uninitialized variables and the like, the non-determinism will certainly cause a program to behave differently with multiple threads active. But if it has bugs in a non-parallel mode, just because they suddenly become visible in parallel search doesn't mean the compiler is broken. It means that the program is very suspect. In your case, the way you are sharing things, the compiler really doesn't even care that you are doing things in parallel because you aren't using the 'light- weight thread' approach to parallel search, which means the compiler has no influence at all over your program... the only danger is in whatever you are sharing among the processes... because you _must_ get the 'volatile' things properly identified or the optimizer will zap you. But once they are right, I don't see any problems at all, even in hundreds of different student programs that are being worked on/tested...
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