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Re: parallelized configure

From: Bob Friesenhahn
Subject: Re: parallelized configure
Date: Wed, 15 Jan 2014 09:06:18 -0600 (CST)
User-agent: Alpine 2.01 (GSO 1266 2009-07-14)

On Wed, 15 Jan 2014, Alexander Holler wrote:

Sure, people do all kind of stuff in build systems. But a lot of tests
which do fly by when configure is called do look like taken from a
standard repository. And many of those tests are pretty simple and
without any dependencies.

It seems that all tests have dependencies. What tests do you think don't have any dependencies? If I specify CC on the configure command line, that may influence the outcome and demonstrates that there are dependencies.

Hmm, I'm using the parallel feature from gnu make very successful since
ext4 with support for nanosecond timestamps appeared (so since many
years). Without a fs with high resolution timestamps I had a lot of
problems, but with high resolution timestamps it works most of the time
like a charm.

This is perhaps off-topic for the Autoconf list. Packages with a lot of recursion and less than 64 target object files per directory, or with some targets which take substantially more time than other targets to compile, do not perform as well as they should for parallel builds on modern CPUs (with 4-64 cores available). If the object files compile very quickly, then there is also less gain from parallel builds since the build framework may take more time than the actual compiles. Lastly, if there are many linking steps, the build time is dramatically increased since linking is sequential in nature, and if there is needless re-linking (a common problem with recursive builds) then the problem is multiplied.

Bob Friesenhahn
GraphicsMagick Maintainer,

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