Parallel make: set -j8 as the default option

Question

I can set number of threads for the build process using -j argument. For example, I have 4 cores +4 virtual. When I write: make -j8 the speed increases

Answer 1

Here's how I've done it:

CORES ?= $(shell sysctl -n hw.ncpu || echo 1)

all:; @$(MAKE) _all -j$(CORES)
_all: install lint test
.PHONY: all _all
…

I've basically "aliased" my default target all to a "private" _all. The command to figure out the number of cores is OSX specific, AFAIK, so you could just improve it to be more cross platform if you will. And because of the ?= assignment, we can just override it with and env variable if/when needed.

EDIT:

You can also append to your MAKEFLAGS from within the makefile itself, like so:

CPUS ?= $(shell sysctl -n hw.ncpu || echo 1)
MAKEFLAGS += --jobs=$(CPUS)
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