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/**
Copyright (c) Scott Gasch
Module Name:
draw.c
Abstract:
Function for detecting a draw by repetition from the search tree.
Author:
Scott Gasch ([email protected]) 19 May 2004
Revision History:
$Id: draw.c 345 2007-12-02 22:56:42Z scott $
**/
#include "chess.h"
FLAG
IsDraw(SEARCHER_THREAD_CONTEXT *ctx)
{
ULONG uPly;
UINT64 u64CurrentSig;
//
// Recognize 50-moves w/o progress draw rule
//
if (ctx->sPosition.uFifty >= 100)
{
return(TRUE);
}
//
// Check for repeated positions if needed.
//
if (ctx->sPosition.uFifty < 4)
{
return(FALSE);
}
u64CurrentSig = (ctx->sPosition.u64NonPawnSig ^
ctx->sPosition.u64PawnSig);
uPly = ctx->uPly - 2;
while(uPly < MAX_PLY_PER_SEARCH)
{
#ifdef DEBUG
if ((GET_COLOR(ctx->sPlyInfo[uPly].mv.pMoved) !=
ctx->sPosition.uToMove) &&
(ctx->sPlyInfo[uPly].mv.uMove != 0))
{
ASSERT(FALSE);
}
ASSERT(ctx->sPlyInfo[uPly].u64Sig == (ctx->sPlyInfo[uPly].u64PawnSig ^
ctx->sPlyInfo[uPly].u64NonPawnSig));
#endif
if (ctx->sPlyInfo[uPly].u64Sig == u64CurrentSig)
{
return(TRUE);
}
if (IS_PAWN(ctx->sPlyInfo[uPly].mv.pMoved) ||
(ctx->sPlyInfo[uPly].mv.pCaptured))
{
return(FALSE);
}
uPly -= 2;
}
//
// Keep looking in the official game record.
//
return(DoesSigAppearInOfficialGameList(u64CurrentSig));
}
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