Default to parallel build

[olafvdspek@…]

Apparently bjam supports parallel builds with -j 4 (for example). Could it default to parallel builds using the number of cores as guideline?

[Steven Watanabe]

I prefer the default of a non-parallel build. It is more obvious and is consistent with other build tools.

[anonymous]

Why is it more obvious?

Unfortunately, yes, most other tools default to serial execution as well. :(

[Vladimir Prus]

Given that it's already possible to set per-user default by putting

option jobs : 4 ;

in any config file, and given that making parallel build the default is controversial, I guess I'll close this issue.

[Tino]

Additionally, parallel builds can only be hardcoded to a specific number. AFAIK bjam can not use a make jobserver in the case that boost is only one part of the whole build process.

I have a build system that builds several software packages for several architectures in one run. I can specify make -j<number> and the make jobserver will use the specified number of jobs.

Except for Boost. I have to hardcode a fixed job number for the boost build (like bjam -j4), that leads to either unused CPU cores, or a lot of overhead, depending on the number of target architectures that are built and the number of CPU cores usable.

[Vladimir Prus]

Tino,

it's not clear to me what you propose? Making b2 interact with make processes running at part of your bigger build does not seem easy.