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Let's say I call Stockfish via

> position fen rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1
>'go movetime 500';

Now, after Stockfish has finished the analysis, what happens if I call stockfish again with the same position?

> position fen rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1
> go movetime 500

Will Stockfish build on the already performed analysis and simply go deeper? Or will it start the analysis anew?

2 Answers 2

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Yes, Stockfish will go deeper if the hash is large enough to make a difference. The default value is 16 MB which is not a lot. After increasing the hash you likely see that the second time the search depth reached after 500 ms is higher than the first time you let Stockfish calculate.

setoption name Hash value 256
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  • Thank you for your answer. By now, I also observed that when I called the Stockfish engine multiple times on the same position, the analysis depth increased - meaning Stockfish remembered earlier analysis results and built on those to improve the analysis. Jan 4 at 11:39
2

One UCI session you mean? To make reproducible experiments or test above, you can compare/contrast multiple calls, by using the UCI purge hash.

"setoption name Clear Hash"

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