27. Processors

It's useful to take advantage of a multi-core machine. The OS does it automatically, but most toolchains don't.

An agnostic way to know the number of cores is via the nproc command from the coreutils Ubuntu package:

$ sudo apt install coreutils
$ nproc

To let the GNU make command leverage the speedup opportunity, provide it via the -j <JOBS> command-line option (the space is optional), like in the following generic example:

$ make -j$(nproc)

Otherwise, declare the special environment variable named MAKEFLAGS, containing that option, to avoid typing it at every call to make:

$ export MAKEFLAGS=-j$(nproc)
$ make