Nodes per second

Nodes per second, usually abbreviated NPS, measures the search speed of a chess engine. A node is, in practical terms, a position within the structure of possible continuations the engine explores while calculating. If an interface reports 2,000,000 NPS, the engine is processing about two million nodes per second according to its own counting method.

The number depends on the processor, the number of processing threads, meaning parallel streams of calculation the processor can handle, engine settings, and how much work the engine performs at each node. For the same engine version under comparable settings, higher NPS generally lets it explore more in the same amount of time and may help it reach greater depth or examine more alternatives.

NPS is not a universal measure of playing strength. Different engines may count nodes differently and spend different amounts of work evaluating each position. Even between versions of one engine, a slower but more accurate evaluation method, such as NNUE, can reduce NPS while making the engine stronger. NPS therefore cannot be converted directly into Elo, a rating scale used to express competitive strength, or used alone to rank different engines.