Author: Robert Hyatt
Date: 20:14:46 09/16/99
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On September 16, 1999 at 17:24:22, J. Wesley Cleveland wrote: >On September 15, 1999 at 09:00:08, Robert Hyatt wrote: > >[snip] >>But it is improving bit by bit. Tim Mann suggested a new hashing scheme that >>is cute for SMP users, as it effectively eliminates the Lock()/UnLock() calls >>without the danger of incorrect hash results. >> > >Does this mean that you can run with multiple threads on a single processor >without significant performance degradation ? Absolutely not. Doing so runs afoul of alpha/beta... IE at the root, you _must_ search the first move before you start searching the others, so you have a reasonable alpha value to search against. A threaded search on a single-cpu machine will always be slower. In Crafty, it is worse because at times, threads are 'spinning' and the O/S has no way of knowing whether a thread is doing useful work or just spinning waiting on another thread to give it work...
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