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Extend by two if the side to move has only one legal move #4894

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Extend by two if the side to move has only one legal move #4894

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ae1ca99
Update search.cpp
TarasVuk Nov 29, 2023
0756f17
Update search.cpp
TarasVuk Dec 1, 2023
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4 changes: 2 additions & 2 deletions src/search.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1328,12 +1328,12 @@ Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, boo
// Step 21. Check for mate and stalemate
// 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.
// return a mate score to trigger double extension.

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

if (!moveCount)
bestValue = excludedMove ? alpha : ss->inCheck ? mated_in(ss->ply) : VALUE_DRAW;
bestValue = excludedMove || ss->inCheck ? mated_in(ss->ply) : VALUE_DRAW;

// If there is a move that produces search value greater than alpha we update the stats of searched moves
else if (bestMove)
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