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By looking at the uci option file of Stockfish 10 I found this line:

o["nodestime"]             << Option(0, 0, 10000);

How exactly does one use nodestime?

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2 Answers 2

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https://github.com/official-stockfish/Stockfish/commit/926f215061311392bc26c7bc4bde5b719dbab4e5

has everything you need. Essentially, it's an option for chess engine testing, not for production use. The option ensures the engine plays perfectly equally during development.

As a user, you shouldn't bother with this option because number of nodes per ms is not something easy to give a value.

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The nodestime option specifies the amount of nodes searched traded for one millisecond of time.

When the nodestime option is set, the engine is limited not by the wall time consumed but by the total amount of nodes searched per game, calculated once per game. The initial time control values are used as source values to be converted to the number of total nodes; however, the source time control settings are not used per turn, but if it were just one turn per game, i.e., the setting of 300 seconds plus 3 seconds increment per move are converted to a total of 303 seconds and then multiplied by 1000 * nodestime; the result is used as the total number of nodes searched per game. Source: a comment by the Stockfish maintainer.

E.g., suppose you specified nodestime = 600, and time control of 300 seconds plus 3 seconds per move (300+3s). In that case, the maximum total number of nodes searched per game by the engine is 303 * 600 * 1000 = 181800000 (one hundred eighty-one million, eight hundred thousand), regardless of how much wall time it will actually take.

However, if you use this option in an engine run from an external time control software, such as cutechess-cli, make sure that the engine running on your computer is able to handle that amount of nodes per second (nodestime*1000). Suppose that your computer and the engine is able to calculate a maximum 900000 nodes per second. In this case, the maximum reasonable value for nodestime is 900, which is 900 nodes per millisecond, or 900000 nodes per second. Otherwise, cutechess-cli will report that your engine lost on time.

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