Some of you may be unaware that recent versions of automake can run in parallel. That is, automake will run in parallel with a degree of (at most) $AUTOMAKE_JOBS. This can speed up the execution time of autogen.pl quite a bit on some platforms. On my cluster at cisco, here's a few quick timings of the entire autogen.pl process (of which, automake is the bottleneck):
$AUTOMAKE_JOBS Total wall time
value of autogen.pl
This is an older Xeon machine with 2 sockets, each with 2 cores.
There's a nice performance jump from 1 to 2, and a smaller jump from 2 to 4. 4 and 8 are close enough to not matter. YMMV.
I just committed a heuristic to autogen.pl to setenv AUTOMAKE_JOBS if it is not already set (https://svn.open-mpi.org/trac/ompi/changeset/23788):
- If lstopo is found in your $PATH, runs it and count how many PU's (processing units) you have. It'll set AUTOMAKE_JOBS to that number, or a maximum of 4 (which is admittedly a further heuristic).
- If lstopo is not found, it just sets AUTOMAKE_JOBS to 2.
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