Author: Miguel A. Ballicora
Date: 07:44:52 04/18/01
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On April 17, 2001 at 11:37:38, Miguel A. Ballicora wrote: >On April 16, 2001 at 15:28:32, Jon Dart wrote: > >> >>If you use the bit scan instructions (e.g. bts), these are way faster on a PIII >>than on an AMD chip. I think the integer multiply on a K6-2 is a lot slower too. > >I don't use assembler, it is just in plain ANSI-C. The good thing is >that allows me to change compilers with no change in the code whatsoever and >that is what I did. >Maybe the MVSC uses some of those instructions when chew up my sources and >gcc don't? > >The weird thing is that K6-2 is not slow _if_ I use gcc. With the rest of >the machines MVSC is better... > >Regards, >Miguel Last night I left the program profiling in MVSC and I found out this morning before going to work that 50% of the cpu time is consumed by a function that the only thing it does is to call clock(), which is an ANSI C standard function!!!! I commented out clock(), only one line in the whole program and the speed increased 300%!!! now, the speed is the same as the executable obtained with gcc. WEIRD... it means that clock() somehow is broken if MVSC is used only in K6-2???? Has anybody ever seen anything like it? is that a bug? I might have to use time() or maybe something non-standard. This teaches me a lesson: you could be compiling something perfectly on one machine but you release a version that could be broken somehow in a particular machine. I will have to test more things when I get home. Regards, Miguel > > >> >>--Jon
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