## Does quiescence search even improve the minimax algorithm?

1

Consider this game state:

d5 captures c6

Quiescence search returns about 8.0 as evaluation because after dxc6 and bxc6 Qxd6 would be played (then Qxd6 by black). A normal player would not play this move but quiescence search includes it in the evaluation and it would result in this end state: which would result in a huge advantage for black.

Is my interpretation of quiescence search wrong?

1

Your logic is flawed because you negated "stand-pat" (i.e. do nothing) and alpha-beta. Let's take a look at the pseudocode (https://www.chessprogramming.org/Quiescence_Search#Pseudo_Code):

int Quiesce( int alpha, int beta ) {
int stand_pat = Evaluate();
if( stand_pat >= beta )
return beta;
if( alpha < stand_pat )
alpha = stand_pat;

until( every_capture_has_been_examined )  {
MakeCapture();
score = -Quiesce( -beta, -alpha );
TakeBackMove();

if( score >= beta )
return beta;
if( score > alpha )
alpha = score;
}
return alpha;
}


Your Qxd6 capture will make return a score far below the alpha. The line:

if( score > alpha )

will prevent your blunder being reported. Instead the engine would report either stand_pat (do nothing), or something like Nf3, Nc3 etc.