Allow inCheck pruning

This is a bit tricky because we don't want
to prune the only legal evasions, even if
with negative SEE. So add an assert to avoid
this subtle bug to slip in later.

STC:
LLR: 2.96 (-2.94,2.94) [0.00,4.00]
Total: 14140 W: 2625 L: 2421 D: 9094

LTC:
LLR: 2.95 (-2.94,2.94) [0.00,4.00]
Total: 11558 W: 1555 L: 1379 D: 8624

bench: 5256717

diff --git a/src/search.cpp b/src/search.cpp
index 1d8139c41d8c764e974616ed5b54c8ee6cb3df34..64cdb325ebce53c3a785747767cf76109b5daa31 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -919,7 +919,6 @@ moves_loop: // When in check search starts from here
 
       // Step 13. Pruning at shallow depth
       if (  !rootNode
 
       // Step 13. Pruning at shallow depth
       if (  !rootNode

-          && !inCheck

           &&  bestValue > VALUE_MATED_IN_MAX_PLY)
       {
           if (   !captureOrPromotion
           &&  bestValue > VALUE_MATED_IN_MAX_PLY)
       {
           if (   !captureOrPromotion


@@ -1121,6 +1120,9 @@ moves_loop: // When in check search starts from here
     // All legal moves have been searched and if there are no legal moves, it
     // must be a mate or a stalemate. If we are in a singular extension search then
     // return a fail low score.
     // All legal moves have been searched and if there are no legal moves, it
     // must be a mate or a stalemate. If we are in a singular extension search then
     // return a fail low score.

+
+    assert(moveCount || !inCheck || excludedMove || !MoveList<LEGAL>(pos).size());
+

     if (!moveCount)
         bestValue = excludedMove ? alpha
                    :     inCheck ? mated_in(ss->ply) : DrawValue[pos.side_to_move()];
     if (!moveCount)
         bestValue = excludedMove ? alpha
                    :     inCheck ? mated_in(ss->ply) : DrawValue[pos.side_to_move()];