Fix rep-draw detection in drop games

In games like Crazyhouse every move is reversible, as captured pieces
can eventually change sides again, and be dropped back on the board.
So we have to search back a full 100 ply for repetitions, passing captures
and Pawn moves.

diff --git a/backend.c b/backend.c
index d78319a..6e24b1a 100644 (file)
--- a/backend.c
+++ b/backend.c
@@ -7666,7 +7666,7 @@ Adjudicate (ChessProgramState *cps)
        //       In any case it determnes if the game is a claimable draw (filling in EP_STATUS).
        //       Actually ending the game is now based on the additional internal condition canAdjudicate.
        //       Only when the game is ended, and the opponent is a computer, this opponent gets the move relayed.
-       int k, count = 0; static int bare = 1;
+       int k, drop, count = 0; static int bare = 1;
        ChessProgramState *engineOpponent = (gameMode == TwoMachinesPlay ? cps->other : (cps ? NULL : &first));
        Boolean canAdjudicate = !appData.icsActive;
 
@@ -7821,10 +7821,12 @@ Adjudicate (ChessProgramState *cps)
 
                 /* Check for rep-draws */
                 count = 0;
+                drop = gameInfo.holdingsSize && (gameInfo.variant != VariantSuper && gameInfo.variant != VariantSChess
+                                              && gameInfo.variant != VariantGreat && gameInfo.variant != VariantGrand);
                 for(k = forwardMostMove-2;
-                    k>=backwardMostMove && k>=forwardMostMove-100 &&
+                    k>=backwardMostMove && k>=forwardMostMove-100 && (drop ||
                         (signed char)boards[k][EP_STATUS] < EP_UNKNOWN &&
-                        (signed char)boards[k+2][EP_STATUS] <= EP_NONE && (signed char)boards[k+1][EP_STATUS] <= EP_NONE;
+                        (signed char)boards[k+2][EP_STATUS] <= EP_NONE && (signed char)boards[k+1][EP_STATUS] <= EP_NONE);
                     k-=2)
                 {   int rights=0;
                     if(CompareBoards(boards[k], boards[forwardMostMove])) {