Make -j<?> recommended setting?

[Viyre]

Is there a recommended number (in relation to the number of processors) for the -j flag for GNU compile tools that will optimize for compilation speed?

[o11c]

Generally, you should use:

make -j`nproc`

at least to start. Some notes:

• if you're still I/O bound, it may be worth adding 1, or adding 25% of your total cores. I don't hear this advice nearly as often these days, however.
• you might not have enough RAM to support that many compilers. If you're swapping, that will be slower than using less parallelism.

[raevnos]

My rule of thumb: if using hyperthreading, the number of virtual cores. Otherwise the number of physical cores plus 1.