Author: Robert Hyatt
Date: 19:11:14 08/19/03
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On August 19, 2003 at 20:06:58, Mathieu Pagé wrote: >Hi, > >The fact: > >I have this question i read at some place that it is faster to unmake a move >than to save the state of the game before moving then restoring it when we want >to unmake the move. > >For the moment my engines did not implement unmake() (it is still buggy). > >My thougth: > >Since bitboard computation are slow (on 32 hardware) i think that it can be >slower to unmake the move than to save the state. I friend of me that is lot >better than me at optimizing code also think that. > >My questions: > >Are you all using unmake() function or there is some of you that found that >saving the state is better ? read the comments from Crafty in main.c. I started out using what is commonly called "copy/make" as that worked well in Cray Blitz. But it didn't work well in the PC. The PC has very limited memory bandwidth, when you compare the speed of memory to the speed/demands of current processors. If you keep the board in cache, and update it there, it is more efficient than to copy it from real memory to real memory... > >In the case that unmake is better. by wich factor ? For me, just faster. Not 300% or any such number, but at least 25% if not more. > >Thanks for your help. > >Mathieu Pagé
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