How Can I define the number of threads for a colcon building process in ROS2?
In previous ros building tools we used "-j {number_of_threads}", but that does not work anymore.
Originally posted by Pablo Iñigo Blasco on ROS Answers with karma: 2982 on 2020-12-22
Post score: 5
There are two independent dimensions of parallelization:
The maximum number of packages processed in parallel when using the parallel executor. This dimension can be limited with the option --parallel-workers NUMBER. It can also be limited to 1 by selecting the sequential executor with --executor sequential.
The maximum number of threads used for a specific package using make. This can be controlled using the environment variable MAKEFLAGS. By setting e.g. export MAKEFLAGS="-j 4" only four threads are used to build a single package. By default colcon-cmake uses the number of available CPU cores (including hyper threading) to limit the number of threads (-j) as well as the system load (-l).
As a result the overall number of threads is the product of packages processed in parallel and maximum number of threads per package.
Originally posted by Dirk Thomas with karma: 16276 on 2020-12-31
This answer was ACCEPTED on the original site
Post score: 7
Comment by brianlmerritt on 2021-11-10:
For anyone finding this, I found that colcon build on a Raspberry Pi 4 can crash, but adding --executor sequential sorted this out without a massive time penalty.
--parallel-workers NUMBER is the syntax you're looking for. "-j N" is a make specific argument.
There's documentation of the parallel executor command line options here: https://colcon.readthedocs.io/en/released/reference/executor-arguments.html
Originally posted by tfoote with karma: 58457 on 2020-12-22
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Post score: 3
yes, export MAKEFLAGS="-j 1" can fix this error:
c++: fatal error: Killed signal terminated program cc1plus
