Author: Mike Hood
Date: 10:14:35 03/09/04
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On March 08, 2004 at 23:49:58, William Penn wrote: >Pretty simple. Reduce hash size. That's the only thing I've found to have a >significant effect when tablebase access starts to churn the hard drive >constantly. Engine speed (kN/s) falls dramatically at that point, perhaps to 10% >or less of normal speed, and never recovers. However using smaller hash size >appears to fix this problem. <-- snip --> I understand what you're saying. Don't fill up all the available memory for hash tables. Leave enough memory for Windows to use as file cache, so that the tablebase files are in memory. Right? If the code is wriiten efficiently, this method of yours shouldn't bring an improvement, and it might even make things worse. Maybe someone can comment on this who knows more about the tablebase access code. Once a tablebase access has been carried out, the result of the tablebase lookup should be stored in the hash tables. The next time the same position is needed, the chess program doesn't need another tablebase lookup, because the result is already in the hash tables. The space needed for a stored position in the hash tables is less than the blocks of data needed for a chunk of the tablebase file in the system cache, so the hash table storage should be more efficient than the system cache. In a simple position with only a few possible transitions to a tablebase position the disk accesses should cease completely within a few seconds. This is the theory, but it isn't backed up by my observations. What's wrong?
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