<div dir="ltr">Hi all,<div><br></div><div>Just to clarify, we are considering making the debian and ubuntu ipopt packages (apt-get install coinor-libipopt) use serial MUMPS instead of parallel. We don't know of anyone exploiting the MPI parallelism. So speak up if you use parallel MUMPS or if you know anyone who does!</div></div><div class="gmail_extra"><br><div class="gmail_quote">On Tue, Sep 30, 2014 at 10:20 AM, Tony Kelman <span dir="ltr"><<a href="mailto:kelman@berkeley.edu" target="_blank">kelman@berkeley.edu</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div dir="ltr">
<div dir="ltr">
<div style="FONT-SIZE:12pt;FONT-FAMILY:'Calibri';COLOR:#000000">
<div>This is an issue that has come up a few times before on the list,
usually</div>
<div>with respect to distribution/Homebrew packages wanting to link Ipopt
to</div>
<div>the MPI version of Mumps. I would like to get feedback from anyone on
the</div>
<div>list who can provide a counterexample to my understanding of current</div>
<div>functionality. The question is:</div>
<div> </div>
<div>Has anyone successfully used the MPI parallel version of MUMPS in</div>
<div>combination with Ipopt? Specifically I’m asking about the mainline</div>
<div>supported release versions of Ipopt, not the work that happened
several</div>
<div>years ago in the experimental distributed-memory parallel branch</div>
<div><a href="https://projects.coin-or.org/Ipopt/browser/branches/parallel" target="_blank">https://projects.coin-or.org/Ipopt/browser/branches/parallel</a>
. I know</div>
<div>it’s possible to use the MPI version of MUMPS with a single process
just</div>
<div>fine, or use MPI to parallelize user function evaluations, or run
separate</div>
<div>completely independent instances of Ipopt solving different
optimization</div>
<div>problems simultaneously. What I’m asking about is running the MUMPS
linear</div>
<div>solver across multiple processes with MPI and achieving measured
parallel</div>
<div>speedup on a single optimization problem.</div>
<div> </div>
<div>I have done this for the multithreaded solvers
WSMP/MA86/MA97/Pardiso,</div>
<div>or to a limited extent via multithreaded BLAS, but never personally
with</div>
<div>MPI MUMPS. I’d like to find out whether it has been done before, in
case</div>
<div>it is possible but just complicated to do. If you’ve tried to do this
but</div>
<div>failed, I'd be interested to hear how far you got.</div>
<div> </div>
<div>Parts of Ipopt outside of MUMPS are not MPI-aware, so running
multiple</div>
<div>copies of an ipopt executable with mpirun will probably duplicate all</div>
<div>computations outside of the linear solver. I’m not actually sure what
would</div>
<div>happen if each copy of ipopt thinks it’s solving an entire
optimization</div>
<div>problem but MUMPS is trying to decompose the linear system over MPI.</div>
<div>I’d be surprised if it worked, but also happy to be proven wrong
here.</div>
<div> </div>
<div>Thanks in advance,</div>
<div>Tony</div>
<div> </div></div></div></div>
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<br></blockquote></div><br></div>