From e67def979d95a6375134a58c3978496bd325205a Mon Sep 17 00:00:00 2001
From: Andrey Sofronov <andrey.sofronov@gmail.com>
Date: Thu, 4 Nov 2010 06:06:53 +0200
Subject: [PATCH] evaluation: fixed again (I hope!) a bug in candidate passers

---
 evaluate.c   | 50 ++++++++++++++++++++++++--------------------------
 extensions.c |  3 +--
 2 files changed, 25 insertions(+), 28 deletions(-)

diff --git a/evaluate.c b/evaluate.c
index f21dc8c..9f115f1 100644
--- a/evaluate.c
+++ b/evaluate.c
@@ -341,6 +341,8 @@ evaluate_pawns(int side)
 	int xside;
 
 	int passed;
+    int next_square;
+    int candidate;
 	int side_defenders, xside_attackers;
 	struct pawn_hash_entry_t *phe;
 
@@ -372,7 +374,7 @@ evaluate_pawns(int side)
 					score_op += passer_score_op[rank_flip[side][_RANK(square)]];
 					score_eg += passer_score_eg[rank_flip[side][_RANK(square)]];
 
-					int next_square = side? square - 8 : square + 8;
+					next_square = side? square - 8 : square + 8;
 					if ((BIT(next_square) & complete) || 
 							(pawn_moves[side][next_square] & PAWNS(xside)))
 						score_eg -= passer_score_eg[rank_flip[side][_RANK(square)]] / 3;
@@ -383,31 +385,28 @@ evaluate_pawns(int side)
 
 				} else if (!(forward_ray[side][square] & PAWNS(xside))) {
 					/* no opponent's pawns on the same file */
+                    candidate = TRUE;
+                    uint64_t candidate_way = forward_ray[side][square] |
+                        BIT(square);
+                    
+                    while (candidate_way) {
+                        next_square = bit_scan_clear(&candidate_way);
+                        
+                        if (rank_flip[side][_RANK(next_square)] == 7)
+                            break;
+
+                        if (popcount(pawn_moves[xside][next_square] & PAWNS(xside)) >
+                            popcount(pawn_moves[side][next_square] & PAWNS(side))) {
+                            candidate = FALSE;
+                            break;
+                        }
+                    }
+
+                    if (candidate) {
+                        score_op += can_passed_score_op[rank_flip[side][_RANK(square)]];
+                        score_eg += can_passed_score_eg[rank_flip[side][_RANK(square)]];
+                    }
 
-					/* how many pawns defend our candidate */
-					side_defenders = popcount(pawn_moves[side][square] &
-							PAWNS(xside));
-					/* how many pawns attack our candidate */
-					xside_attackers = popcount(pawn_moves[side][square] & \
-							PAWNS(xside));
-
-					if (xside_attackers <= side_defenders) {
-						/* pawn is well protected */
-
-						/* how many pawns can support our candidate */
-						side_defenders = popcount((passer_mask[xside][square - \
-									(side == WHITE? 8 : -8)] & \
-									isolated_mask[_FILE(square)]) & PAWNS(side));
-						/* how many pawns can stop our candidate */
-						xside_attackers = popcount(passer_mask[side][square] & \
-								PAWNS(xside));
-
-						if (xside_attackers <= side_defenders) {
-							/* true passed pawn candidate */
-							score_op += can_passed_score_op[rank_flip[side][_RANK(square)]];
-							score_eg += can_passed_score_eg[rank_flip[side][_RANK(square)]];
-						}
-					}
 				}
 			}
 			if (isolated_mask[_FILE(square)] & PAWNS(side)) {
@@ -592,7 +591,6 @@ evaluate_knights(int side)
 				if (pawn_moves[xside][square] & PAWNS(side)) {
 					/* knight is supported by our pawn */
 					position_score[OPENING][side] += knight_outpost[side][square];
-					position_score[ENDGAME][side] += knight_outpost[side][square];
 				}
 
 		/* calculate mobility */
diff --git a/extensions.c b/extensions.c
index 7b98cf4..2f8db11 100644
--- a/extensions.c
+++ b/extensions.c
@@ -45,8 +45,7 @@ get_extensions(int move, int in_check, int move_is_check, int depth, int ply)
 
 	/* don't reduce passed pawn moves */
 	if (square64[GET_TO(move)] == PAWN)
-		if (!(PAWNS(brd.wtm) & passer_mask[1 ^ brd.wtm][GET_TO(move) + \
-					(brd.wtm ? -8 : 8)]))
+		if (!(PAWNS(brd.wtm) & passer_mask[1 ^ brd.wtm][GET_TO(move)]))
 			return 0;
 
 #ifdef STATISTIC_COUNTERS
-- 
2.11.4.GIT