Author: Dann Corbit
Date: 14:43:19 04/16/01
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On April 16, 2001 at 17:28:15, Uri Blass wrote: >I think it is possible to do deterministic programs that use more than one >processor by using more than one processor only to do things faster. > >Examples: > >1)using more than one processor to calculate the evaluation function faster. >2)using more than one processor to generate the pseudo legal moves faster. > >I guess that it is more simple to do it than using more than one processor for >the search when one of the disadvantages is the fact that the program is only >for x processors when the programmer decides about x in the design decision. > >Here is example of using two proccesors to calculate >x1+x2+....x64 (The evaluation function may have a number of this type) > >step 1:proccesor 1 calculates y=x1+x2+....x32 >step 2:proccesor 2 calculates z=x33+x34....+x64 at the same time of step 1 >step 3:processor 2 gives z to processor 1 >step 4:processor 1 caluclates y+z > >This is only for 2 processors but by the same idea it is possible to change a >program to be only for 8 processors if 8 processors are going to be used against >kramnik. > >I have some questions about it > >1)Am I right to assume that writing a program only for x processors by this way >is more simple then using more than one processor in the regular way? >2)What is the speed improvement that it is possible to get by using more than >one processor only to calculate things faster. >3)Did programmers try to use more than one processor in order to calculate a >more complex evaluation function and not in order to search deeper? With more than one processor, you clearly have to deal with resource contention one way or another. Otherwise you will definitely crash or get single-threaded speed [neither of which is desirable] ;-) If you don't access the hash table with both CPUs, I think it will quickly become the rate limiting factor. The way to get the biggest boost is pretty simple. Use more CPU's on whatever is the biggest bottleneck. I suspect they will be: 1. Search algorithm (including Negascout + eval) 2. Hash operations Everything else will be trivial and unimportant.
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