Author: Robert Hyatt
Date: 06:46:05 09/25/01
Go up one level in this thread
On September 25, 2001 at 08:41:25, Dieter Buerssner wrote:
>I made a small, not very scientific experiment, to get a feeling
>for the significance of hash collisions.
>
>For this, I tested 22 positions of WAC (the ones, that I would call the
>most difficult ones). I tested those for 2 million nodes. Yace will use
>HTs in quiescence search, so the table gets filled very fast (on average
>almost 80% of the searched nodes get stored). I used only a small HT
>for this test - 1e6 bytes, which is about 80000 entries - to make sure,
>that the table really gets overloaded. I made 4 runs of the test positions:
>with a 32/16/12 and 8-bit hash-values (the hash index is calculated
>independently of these). Here are the results. I hope, it is more or
>less self explaining. The number of hash errors given, is just the
>ones that were detected by checking for the legality of the move. This is
>only done, when the hash info would give a cutoff, or an adjustment of
>the search window. When the move is not legal, no cutoff/adjustement of search
>bound is allowed.
>
>TEST test.ci by Yace 0.99.56 32-bit hash search_nodes 2000000 Tue Sep 25
>14:14:58 2001
>table_add=30392714, table_store=30392714, table_probe=38930034, 29.22% found
>hash_errors 0, egtb_probe=0, egtb_found=0
> 22 tested, 19 found, 3 not found, mates 4, time 118.71
>test nodes 17047943 win nodes 11047915 mate nodes 2601918
>win time 78.65 mate time 17.41 av depth 8.045 (nm 8.222) maxdepth 32 tu 74
Remember what I said earlier. The collision probability is not the only
thing you have to deal with. You have to have _enough_ collisions so that
the root score changes. This is a harder thing to cause. Your very small
table is probably helping you avoid this rather than hurting. Because you
are probably depth-preferred and are not adding much to the table after the
first few seconds, at a guess...
4
>
>TEST test.ci by Yace 0.99.56 16-bit hash search_nodes 2000000 Tue Sep 25
>14:21:48 2001
>table_add=30433572, table_store=30433572, table_probe=38892887, 28.97% found
>hash_errors 22, egtb_probe=0, egtb_found=0
> 22 tested, 19 found, 3 not found, mates 4, time 116.31
>test nodes 16872328 win nodes 10872318 mate nodes 2669471
>win time 76.86 mate time 17.11 av depth 8.045 (nm 8.222) maxdepth 32 tu 748
>
>TEST test.ci by Yace 0.99.56 12-bit hash search_nodes 2000000 Tue Sep 25
>14:29:01 2001
>table_add=30559112, table_store=30559112, table_probe=38955354, 28.70% found
>hash_errors 441, egtb_probe=0, egtb_found=0
> 22 tested, 19 found, 3 not found, mates 4, time 122.58
>test nodes 17320105 win nodes 11320088 mate nodes 2614227
>win time 82.12 mate time 17.71 av depth 8.045 (nm 8.222) maxdepth 34 tu 777
>
>TEST test.ci by Yace 0.99.56 8-bit hash search_nodes 2000000 Tue Sep 25
>14:36:32 2001
>table_add=32512573, table_store=32512573, table_probe=40699069, 26.80% found
>hash_errors 7128, egtb_probe=0, egtb_found=0
> 22 tested, 17 found, 5 not found, mates 3, time 167.31
>test nodes 23403260 win nodes 13403242 mate nodes 2620719
>win time 99.20 mate time 17.77 av depth 7.864 (nm 7.947) maxdepth 32 tu 734
>
>Only in this last run, the search got very confused at times. One example:
>
> 161407 1.228 0.39 5t+ 1.Nfg5 fxg5 2.Nf6 Ba3 3.bxa3 Rb7 4.axb5 axb5
> {-80}
> 167981 1.300 0.93 5++ 1.Nfg5 bxa4 2.Nxh7 Rxd4 3.Nxf8+ Kg8 {330}
> 170673 1.333 1.93 5++ 1.Nfg5 Bc5 2.dxc5 Rd4 {260}
> 172307 1.361 6.93 5++ 1.Nfg5 Rd5 2.Nxh7 Nd7 3.Nxf8+ Kg8 4.Nxd7 Bxd7H
> 5.axb5H {570}
> 179777 1.405 Mat04 5t 1.Nfg5 fxg5 2.Nf6 Bxf6 3.Be4 Kg8 4.Qxh7#H {-690}
> 182542 1.428 Mat04 5. 1.Nfg5 fxg5 2.Nf6 Bxf6 3.Be4 Kg8 4.Qxh7# {-690}
> 183483 1.433 Mat04 6t 1.Nfg5 fxg5 2.Nf6 Bxf6 3.Be4 Kg8 4.Qxh7# {-690}
> 201820 1.493 Mat03 6t+ 1.Nxf6 Bxf6 2.Ng5 Bxg5 3.Qxf8+ {-190}
> 203865 1.505 Mat04 6t- 1.Nxf6 Bxf6 2.Ng5 Bxg5 3.Qxf8+ Qxf8 4.Bxc6
> {-1111}
> 203865 1.505 Mat04 6t 1.Nfg5 fxg5 2.Nf6 Bxf6 3.Be4 Kg8 4.Qxh7# {-690}
> 227459 1.595 Mat04 6. 1.Nfg5 fxg5 2.Nf6 Bxf6 3.Be4 Kg8 4.Qxh7# {-690}
> 239645 1.648 14.24 7-- 1.Nfg5 fxg5 2.Qxe6
> 263834 1.745 13.24 7-- 1.Nfg5 fxg5 2.Qxf8+ Bxf8 3.Nxg5
> 268473 1.770 8.24 7-- 1.Nfg5 fxg5 2.Qxf8+ Bxf8 3.Nxg5
> 1152818 9.489 -2.45 7t 1.Nfg5 fxg5 2.axb5 Rg8 3.bxa6 Nxa6 4.e3 Rg6
> 5.Qh5 Kg8 {HT} {-350}
> 1309369 10.801 -2.44 7t+ 1.Nc5 bxa4
> 1724535 13.784 0.43 7t 1.Nc5 Bxc5 2.dxc5 Rd5 3.axb5 cxb5 4.b4 Nc6
> 5.Rfd1 {-80}
> 1978437 15.616 0.44 7t+ 1.axb5 cxb5 2.Nfg5 Rd5 3.Nxh7 Bb7 4.Nxf8+ Kg8
> {490}
> 2000006 15.750 0.44 7t 1.axb5 cxb5 2.Nfg5 Rd5 3.Nxh7 Bb7 4.Nxf8+ Kg8
> {490}
> 2000006 15.758 0.44 7u. 1.axb5 cxb5 2.Nfg5 Rd5 3.Nxh7 Bb7 4.Nxf8+ Kg8
> {490}
>Regards,
>Dieter
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