Author: Gerd Isenberg
Date: 06:49:49 09/26/03
Go up one level in this thread
On September 26, 2003 at 07:01:49, Ricardo Gibert wrote: >On September 25, 2003 at 13:02:22, Tord Romstad wrote: > >>On September 25, 2003 at 11:28:55, Robert Hyatt wrote: >> >>>On September 25, 2003 at 09:48:33, Tord Romstad wrote: >>> >>>>On September 24, 2003 at 16:28:57, Robert Hyatt wrote: >>>> >>>>>I try to use _most_ of main memory for serious games, and if you have a >>>>>1 gig machine, I generally use something like hash=784M, hashp=40M, >>>>>cache=128M, and go from there... >>>> >>>>Interesting. Is a 40M pawn hash table really useful for Crafty? How big >>>>are your pawn hash entries? My pawn hash table contains just 256 entries, >>>>where each entry is 128 bytes. The last time I tried, increasing the size >>>>of the table gave just a very small speedup (less than 2%, if I recall >>>>correctly). >>>> >>>>Tord >>> >>> >>>I've never carefully tested this, but 256 entries seems _way_ small. Just >>>look at how many different possible pawn positions there are. >> >>I decided to experiment with this again. I let my engine analyze the >>position after 1. d4 d5 2.c4 e6 3. Nc3 Nf6 4. Bg5 Be7 to a depth of >>10 plies with different pawn hash table sizes. Here are the results >>(the first column is the number of entries, the second column is the >>number of seconds needed to complete 10 plies): >> >> 1 70.59s >> 2 60.08s >> 4 58.28s >> 8 57.25s >> 16 55.74s >> 32 55.24s >> 64 54.38s >> 128 54.18s >> 256 53.76s >> 512 53.53s >> 1024 53.32s >> 2048 53.05s >> 8192 52.68s >> 16384 52.25s >> 32768 52.09s >> 65536 51.87s >>131072 51.82s >>262144 51.85s >>524288 51.88s >> >>As you can see, the speed gain by increasing the number of entries from >>256 is not very big, and increasing the size beyond 65536 entries seems >>completely useless. >> >>Of course, it is possible that a different position would have given >>different results. >> >>Tord > >This is a surprise! Not for me, even with a one entry Pawn hash you got a lot of hits, as Tony already mentioned. Try fine70 with one entry ;-) The advantage of one entry is that you don't bother about index calculation. But seriously, i found 32K-64K entries an appropriate pawn hash table size. >If your results are replicated by other programs, it would >be *very* interesting. Have you any insights on why a bigger phash is not really >useful? I guess some diminishing returns, due to irreversibility of pawn moves. May be more Cache or even TLB misses? Gerd
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