Author: Jeremiah Penery
Date: 22:30:58 01/18/00
Go up one level in this thread
On January 18, 2000 at 23:53:45, Dann Corbit wrote:
>On January 18, 2000 at 23:36:20, Tom Kerrigan wrote:
>
>>On January 18, 2000 at 23:17:01, Dann Corbit wrote:
>>
>>>Conversely, we might allocate a *single* hash entry. Either method ought to
>>>dumb the program down just a touch.
>>>;-)
>>
>>Having a single hash entry will not make the program much worse.
>I am surprised to hear that. I have seen curves drawn which show a massive rise
>in ELO for the first few megabytes, which then tapers off to what appears to be
>a logarithmic increase.
Here is a post Bob made a while back in RGCC, comparing the time taken and the
number of nodes searched for a certain position to a fixed depth, varying the
hash sizes each time. I'm not sure of what version of Crafty it was - whatever
was current on Feb. 24 of 1999.
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Komputer Korner <korner1@netcom.ca> wrote:
: Yes but it doesn't explain the drastic performance hit if the table is
: not quite "large" enough to fill the last complete iteration.
You will have to define 'drastic'. Here is some output for crafty, searching to
a fixed depth in a middlegame position. I varied the hash from very small to
very large and recorded the time it took to reach the same depth (only one
processor used to avoid the problem of SMP non-determinism). search speed is
about 200K nodes per sec on this PII/400/xeon machine (one processor).
hash table sizes
time bytes entries nodes searched
-------------------------------------------
13:13 96K 6K 157,085,451
12:03 192K 12K 142,633,162
10:31 384K 24K 123,762,238
9:28 768K 49K 110,838,220
8:38 1.5M 98K 100,802,339
7:48 3M 196K 90,979,000
7:22 6M 392K 85,975,960
6:53 12M 800K 80,347,212
6:32 24M 1.5M 76,465,119
6:22 48M 3.0M 74,738,532
6:13 96M 6.0M 73,253,374
6:05 192M 12.0M 71,581,397
6:03 384M 24.0M 71,156,722
Here is the position I searched, to a depth of 11 plies:
[D]3rr1k1/1p2b1pp/p1b1p3/8/PnBBq3/2Q2N2/1PP3PP/R4R1K b - - 0 1
---------------
Jeremiah
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