Author: Robert Hyatt
Date: 18:47:15 06/13/04
Go up one level in this thread
On June 13, 2004 at 16:46:14, Tord Romstad wrote:
>On June 13, 2004 at 14:24:57, GeoffW wrote:
>
>>Hi
>>
>>I was thinking how I would add pawn hashing to my program. Having read a little
>>of the Crafty source I have a rough grasp of the idea, however there are a
>>couple of things I am hazy on.
>>
>>Q1)
>>I understand the pawn hash score stored must not contain any piece related
>>scoring as that must be factored in later. In my program even the simple choice
>>of which pawn position look up table is determined by the phase of the game, i.e
>>it will be piece dependent. How would I get over that obstacle ? Score the pawns
>>for end game, opening and middle in the hash, and choose which one to use later
>>?
>
>I don't store any scores at all in the pawn hash table, but just lots of
>computations
>which is used by the evaluation function. I store things like the location of
>all
>passed, isolated, double or backward pawns, pawn chains, number of pawns on
>black/white squares for both sides, a classification of the centre (open,
>closed,
>semi-closed, etc.), and so on.
>
>>Q2)
>>Crafty uses an 8 bit bitmap to store file for passers, this is ok for a bitboard
>>program as it is probably trivial to find the exact location later. However for
>>a non bitboard program it is non trivial to find the exact locations. Do I have
>>any alternative but to store the passer locations in the hash ? That would be 16
>>bytes just for the passed pawns for both sides?
>
>My program also doesn't use bitboards. I simply store all the exact locations.
>This is not a problem, you can afford to use lots of space for your pawn hash
>table entries. My entries are 128 bytes big. Keep in mind that the number of
>pawn structures seen in a single search isn't very big, and that this means that
>you don't need to store a big number of entries. I found that increasing the
>pawn hash table size beyond 256 entries gave only a tiny increase in speed
>(about 3%, IIRC).
>
>Tord
I don't know what kind of tree you are searching, but my numbers are so far off
from yours it is not funny:
Crafty with 12K pawn hash, 24 bytes per entry, searching initial position with
no book for one minute:
time=1:00 cpu=98% mat=0 n=13646141 fh=88% nps=227K
ext-> chk=253094 cap=88326 pp=5587 1rep=12141 mate=22
predicted=0 nodes=13646141 evals=5740196 50move=0
endgame tablebase-> probes=0 hits=0
hashing-> 21%(raw) 20%(depth) 99%(sat) 82%(pawn)
hashing-> 0%(exact) 13%(lower) 0%(upper)
82% pawn hits.
crafty with default 768K pawn hash:
time=1:00 cpu=99% mat=0 n=17138483 fh=87% nps=285K
ext-> chk=333036 cap=108663 pp=6360 1rep=16404 mate=34
predicted=0 nodes=17138483 evals=7193047 50move=0
endgame tablebase-> probes=0 hits=0
hashing-> 20%(raw) 19%(depth) 99%(sat) 91%(pawn)
hashing-> 0%(exact) 13%(lower) 0%(upper)
91% pawn hits.
Crafty with 12M pawn hash:
time=1:00 cpu=99% mat=0 n=19443424 fh=88% nps=324K
ext-> chk=391251 cap=121056 pp=7111 1rep=19336 mate=61
predicted=0 nodes=19443424 evals=8055682 50move=0
endgame tablebase-> probes=0 hits=0
hashing-> 20%(raw) 19%(depth) 99%(sat) 95%(pawn)
hashing-> 0%(exact) 13%(lower) 0%(upper)
95% pawn hits. Notice the NPS. 227K, with small hashp, 285K with default, 324K
with 12M. Here is the time to finish 11 ply on my 750mhz laptop:
11-> 34.93 0.14 1. e4 Nc6 2. Nf3 e6 3. Nc3 Nf6 4. e5
Ng4 5. d4 Bb4 <HT>
11-> 27.41 0.14 1. e4 Nc6 2. Nf3 e6 3. Nc3 Nf6 4. e5
Ng4 5. d4 Bb4 <HT>
11-> 24.39 0.14 1. e4 Nc6 2. Nf3 e6 3. Nc3 Nf6 4. e5
Ng4 5. d4 Bb4 <HT>
If you only get 3% better after making yours bigger, somehow you and I are doing
something so completely different that it boggles the mind. I got 10% faster
going from 3/4M to 12M in the above. 20% going from 12K to 768K.
Those are all current crafty on a Sony VAIO 750mhz laptop.
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