Author: Dan Newman
Date: 15:52:30 09/25/99
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On September 25, 1999 at 06:59:06, Frank Phillips wrote: >My program compiled with MSVC++ 6 (Enterprise) is almost 30% slower than the >same code with the same options compiled with MSVC++V5, which is a bit >disappointing. The simple test I did was a fixed depth search for six middle >game positions. More worrying than the decrease in speed is the number of nodes >to reach the fixed depth which have increased under VC6. > >Usual type of program – PVS with hash tables. Mixture of bitboards and offset >arrays. > >What am I missing? > >Frank I once had a problem like this when compiling with different compilers (Watcom, MS, GNU)--I got a different answer with each. I finally traced it down to my use of the qsort() routine, which I used to sort moves at the root. Each compiler had a different implementation of course. I quickly replaced it with some C code. You could try compiling with optimizations off and see what happens. I'm not sure what that would tell you though; I guess it wouldn't pin down whether it's your code or the compiler. (In 25 yrs of programming I've only found perhaps 3 bugs that I could attribute to the compiler. There were of course a larger number of bugs that I never figured out.) I guess what I would do is look in detail at the node count for each ply to see where it starts going wrong (the earlier the better). I'd look for a position that displays this difference early on, if possible. Then I'd put in a lot of print statements to see what's different, etc. -Dan.
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