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Subject: Re: Yet again: Hashing and FINE 70

Author: Tim Foden

Date: 04:00:30 12/19/00

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On December 18, 2000 at 17:25:38, Scott Gasch wrote:

>Realized after I sent last message that these might help you out a little too:
>
>   Hash probes:    357103                     Hash stores:    159816
>     hit exact:      2084                     store exact:      1166
>     hit upper:     13164                     store upper:     52337
>     hit lower:    164747                     store lower:    106313
>  hit unusable:    101410                    store nulllw:         0
>     deep/fast: 257292 / 68267 (72.05% / 19.12%)
>    Efficiency: 91.17%
>
>Probes is calls to HashLookup.  Hit exact is exact hits with enough draft to
>use.  Hit upper/lower is enough draft and usable with current A/B to cause a
>cutoff.  Unusable is not enough draft (but still ordered first).
>
>Stores are exactly what you think.  Store nulllw is lower bounds stored after a
>null move cutoff.  The deep/fast numbers are for the two halves of the
>transposition table... one implements deeper-only replace and the other always
>replaces.  These tables are the same size currently although I would be
>interested in anyone with experience shrinking the always replace table...  The
>efficiency numbers include unusable hits (basically if I match a sig in the hash
>the numerator of the efficiency ratio increases.  The denominator is the total
>probes).  These numbers are from the output of that same 5 sec search I am
>following up to.
>
>Good luck!
>Scott

Hi Scott,

I have added some output to show hash table stats in my current version.
This may have shown something...

From a 5 sec search:
 trans:  probes=383355  hits=381465 (99.51)  draft=376184 (98.13)
 trans:  exact=501 (0.13)  upper=19463 (5.08)  lower=1424 (0.37)

From a 30 sec search:
 trans:  probes=2155300  hits=2151794 (99.84)  draft=2144458 (99.50)
 trans:  exact=662 (0.03)  upper=69608 (3.23)  lower=4388 (0.20)

As you can see, although GLC is getting lots of hits (>98%), it is getting
nowhere near the number of cutoffs (<6%).  In particular the number of lower
bound cutoffs is very small compared to yours.

This may well be getting me on to the right track... thanks for your help.

Cheers, Tim.



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