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/**
Copyright (c) Scott Gasch
Module Name:
pawnhash.c
Abstract:
Pawn structure score hashing code.
Author:
Scott Gasch ([email protected]) 14 Jun 2004
Revision History:
$Id: pawnhash.c 345 2007-12-02 22:56:42Z scott $
**/
#include "chess.h"
PAWN_HASH_ENTRY *
PawnHashLookup(SEARCHER_THREAD_CONTEXT *ctx)
/**
Routine description:
Called by eval with a pointer to a POSITION, look in our pawn hash
to see if we have an entry that matches the pawn structure in the
POSITION. If so, "check out" that entry and return a pointer to
it.
Note: a single direct-indexed probe, no multi-probing scheme --
ctx->rgPawnHash is embedded per-thread inside SEARCHER_THREAD_
CONTEXT (chess.h), so there's no cross-thread contention to
avoid here in the first place.
Parameters:
POSITION *pos
Return value:
PAWN_HASH_ENTRY *
**/
{
POSITION *pos = &(ctx->sPosition);
ULONG u = (ULONG)pos->u64PawnSig & (PAWN_HASH_TABLE_SIZE - 1);
return(&(ctx->rgPawnHash[u]));
}
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