Author: Miguel A. Ballicora
Date: 10:04:49 12/05/01
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On December 05, 2001 at 12:42:07, Ed Schröder wrote: >On December 05, 2001 at 06:46:07, Severi Salminen wrote: > >>>>#define color(target) (((info[target])>>3)&3) >>>> >>>> >>>>my data.c file includes >>>> >>>>int info[64]; >>>>int side; >>>>int direction[64][64]; >>>>int kingsquare[2]; >>>>int pin[64]; >>>> >>> >>>Perhaps the data types could be a reason for some microscopic effects. If the >>>variable "side" is for instance of type "short", the compiler has to zero-extend >>>the variable to word-size before indexing (because of the array access). >> >>But as you can see the variables are all ints. So no type conversions needed. I >>believe there is just some stupid alignment thing happening or something and >>that's why the program slows down a bit. I'd use side instead of color(sq) and >>hopefully the speedup will show up later. >> >>Severi > > >You could try to decrease the > >int direction[64][64]; > >by one, thus: > >int direction[63][64]; > >The result might be the compiler doesn't have to do an expensive multiply >(*65) but is able to do a simple shift-left bits instruction (SHL 6) which >shift left the bytes 6 times, thus a multiply by 64. I do not understand. Why would a compiler want to multiply by 65 in the first place? Isn't 64 in both cases as determined by the second index? Regards, Miguel > >Ed
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