Cores and Threads Management
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Maximum number of threads (cores) used by the analysis.
Default is hardware-dependent, min 1, max 8 (Standard) or 128 (Pro).
If you intend to use your computer for other purposes while analyzing chess positions, set "Threads" to a value smaller than the the number of physical cores of your computer - for example, use 3 on a quad-core computer. This will leave one core available for other applications while the chess analysis runs in the background.
Additionally you can run the engine at “Lower than normal” priority to reduce its impact on the computer's responsiveness. Most chess GUI will provide this option, for example:
- Arena has a "Lower than normal process priority" checkbox in the Engine Management Options.
- Shredder GUI will automatically run engines at lower priority.
- Fritz/ChessBase has a "Priority Below Normal" checkbox in the dialog for creating the UCI engine.
If your computer supports hyper-threading it is usually recommended not using more threads than physical cores. The additional hyper-threads will yield about 25% to 30% extra node speed, but the inefficiency of the parallel alpha-beta search with the higher number of threads will partially offset this speed gain. This means that the extra hyper-threads will produce only a small increase in Elo – probably at most 10 Elo.
To illustrate this, in a 12 vs 24 threads test match on a 12-core computer (Intel Xeon processor) the outcome after 1500 games was +7 ±10 Elo in favor of the 24-thread engine. Even with 1500 games played the measured Elo difference was still inside the error margin!
If your CPU can be overclocked it may actually be wiser not to use hyper-threading. By not using the hyper-threading you will reduce the thermal load of the CPU which will allow you to reach a higher overclocking frequency.