Simplify unstoppable pawns evaluation

R-Peleg · mcostalba · commit bebd6e16f6e8 · 2013-09-10T23:02:05.000+02:00
No functional change
diff --git a/src/evaluate.cpp b/src/evaluate.cpp
@@ -1002,19 +1002,19 @@ Value do_evaluate(const Position& pos, Value& margin) {
             {
                 b2 = supporters & in_front_bb(winnerSide, rank_of(blockSq + pawn_push(winnerSide)));
 
-                while (b2) // This while-loop could be replaced with LSB/MSB (depending on color)
+                if (b2)
                 {
-                    d = square_distance(blockSq, pop_lsb(&b2)) - 2;
+                    d = square_distance(blockSq, backmost_sq(winnerSide, b2)) - 2;
                     movesToGo = std::min(movesToGo, d);
                 }
             }
 
             // Check pawns that can be sacrificed against the blocking pawn
-            b2 = pawn_attack_span(winnerSide, blockSq) & candidates & ~(1ULL << s);
+            b2 = pawn_attack_span(winnerSide, blockSq) & candidates & ~SquareBB[s];
 
-            while (b2) // This while-loop could be replaced with LSB/MSB (depending on color)
+            if (b2)
             {
-                d = square_distance(blockSq, pop_lsb(&b2)) - 2;
+                d = square_distance(blockSq, backmost_sq(winnerSide, b2)) - 2;
                 movesToGo = std::min(movesToGo, d);
             }
 
@@ -1033,12 +1033,8 @@ Value do_evaluate(const Position& pos, Value& margin) {
             kingptg = (minKingDist + blockersCount) * 2;
         }
 
-        // Check if pawn sacrifice plan _may_ save the day
-        if (pliesToQueen[winnerSide] + 3 > pliesToGo + sacptg)
-            return SCORE_ZERO;
-
-        // Check if king capture plan _may_ save the day (contains some false positives)
-        if (pliesToQueen[winnerSide] + 3 > pliesToGo + kingptg)
+        // Check if pawn sacrifice or king capture plan _may_ save the day
+        if (pliesToQueen[winnerSide] + 3 > pliesToGo + std::min(kingptg, sacptg))
             return SCORE_ZERO;
     }
 

Original file line number	Diff line number	Diff line change
`@@ -1002,19 +1002,19 @@ Value do_evaluate(const Position& pos, Value& margin) {`
`1002`	`1002`	`{`
`1003`	`1003`	`b2 = supporters & in_front_bb(winnerSide, rank_of(blockSq + pawn_push(winnerSide)));`
`1004`	`1004`
`1005`		`- while (b2) // This while-loop could be replaced with LSB/MSB (depending on color)`
	`1005`	`+ if (b2)`
`1006`	`1006`	`{`
`1007`		`- d = square_distance(blockSq, pop_lsb(&b2)) - 2;`
	`1007`	`+ d = square_distance(blockSq, backmost_sq(winnerSide, b2)) - 2;`
`1008`	`1008`	`movesToGo = std::min(movesToGo, d);`
`1009`	`1009`	`}`
`1010`	`1010`	`}`
`1011`	`1011`
`1012`	`1012`	`// Check pawns that can be sacrificed against the blocking pawn`
`1013`		`- b2 = pawn_attack_span(winnerSide, blockSq) & candidates & ~(1ULL << s);`
	`1013`	`+ b2 = pawn_attack_span(winnerSide, blockSq) & candidates & ~SquareBB[s];`
`1014`	`1014`
`1015`		`- while (b2) // This while-loop could be replaced with LSB/MSB (depending on color)`
	`1015`	`+ if (b2)`
`1016`	`1016`	`{`
`1017`		`- d = square_distance(blockSq, pop_lsb(&b2)) - 2;`
	`1017`	`+ d = square_distance(blockSq, backmost_sq(winnerSide, b2)) - 2;`
`1018`	`1018`	`movesToGo = std::min(movesToGo, d);`
`1019`	`1019`	`}`
`1020`	`1020`
`@@ -1033,12 +1033,8 @@ Value do_evaluate(const Position& pos, Value& margin) {`
`1033`	`1033`	`kingptg = (minKingDist + blockersCount) * 2;`
`1034`	`1034`	`}`
`1035`	`1035`
`1036`		`- // Check if pawn sacrifice plan _may_ save the day`
`1037`		`- if (pliesToQueen[winnerSide] + 3 > pliesToGo + sacptg)`
`1038`		`- return SCORE_ZERO;`
`1039`		`-`
`1040`		`- // Check if king capture plan _may_ save the day (contains some false positives)`
`1041`		`- if (pliesToQueen[winnerSide] + 3 > pliesToGo + kingptg)`
	`1036`	`+ // Check if pawn sacrifice or king capture plan _may_ save the day`
	`1037`	`+ if (pliesToQueen[winnerSide] + 3 > pliesToGo + std::min(kingptg, sacptg))`
`1042`	`1038`	`return SCORE_ZERO;`
`1043`	`1039`	`}`
`1044`	`1040`