Re: larger hashsize -> slower "book add"

[Simon Waters]

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Martin Mačok wrote:
>
> when I enlarge HASHSLOTS and PAWNSLOTS in common.h then generating
> book is much slower. Larger tables -> slower generating.
> (But of course: larger tables -> faster engine, tested with "go")
>
> My system is Athlon 800/256MB, Mandrake 8.2 Linux, gcc-2.96

Which version of GNU Chess?

Did you check if the process is swapping? i.e. if physical memory is
exhausted.

How much slower?

Increasing hashtables will typically slow the program down, as more
memory operations are performed (and accessing RAM is much slower than
accessing CPU cache). Usually the hash will result in considerable
saving in moves to evaluate more than offsetting the slow down. The
effect of this is usually only a few percent.

HASHSLOTS and PAWNSLOTS are largely unconnected to the book code.

I have not seen any evidence that PAWNSLOTS is in much need of
increasing, there are only so many pawn structures you can get to from a
typical position. But I haven't examined it rigorously.

Hashsize will get easier to change with GNU Chess 5.06.
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