[Scons-users] build time

[Greg Ward]

On 03 July 2012, TOM TANNER (BLOOMBERG/ LONDON) said:

> I'm converting our build from a.n. other system, and one issue we

> have is that a 'do nothing' build takes 20 minutes to work out it has

> to do nothing.


Wow. Just out of curiosity, how many source files do you have? How
many build outputs?

(I'm working on rewriting our build with scons, and I'm handling maybe
16,000 of our source files. It's up to 16 sec for a null build, and
I'm getting pretty antsy about it. That's about 15 seconds longer than
I would like.)


> This is a *little* better on scons, but I notice that even if I give

> it a lot of threads, it spends all its time hanging around for the

> infamous global interpreter lock, even though we have a few spare

> CPUs.


Are you sure it's threading and not the toposort? My understanding is
that one of the skeleton's in SCons' closet is that its toposort
implementation is O(N^2), whereas a textbook toposort is O(N + E)
(number of nodes plus number of edges in the dependency graph).

       Greg
-- 
Greg Ward                                http://www.gerg.ca/
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