1 files changed, 79 insertions, 0 deletions
diff --git a/src/draw.c b/src/draw.c
new file mode 100755
index 0000000..75d1cd4
--- /dev/null
+++ b/src/draw.c
@@ -0,0 +1,79 @@
+/**
+
+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));
+}