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From: | Meketon, Marc |
Subject: | RE: [Help-glpk] memory usage seems very high |
Date: | Sat, 13 Jun 2009 09:22:33 -0400 |
A couple of strange things: First, when I run your model on my Windows
box, it doesn’t run completely. In particular, it generates a few of
your constraints (c1 to cc) and then nicely stops. The output looks like: Reading model section from big.mod... 7103 lines were read Generating z... Generating c0... Generating c1... Generating c2... Generating c3... Generating c4... Generating c5... Generating c6... Generating c7... Generating c8... Generating c9... Generating ca... Generating cb... Generating cc... So it does not get to the optimization
piece. I wonder if that’s a window’s limitation because you have
very long lines. Second, your model (from your output
below) is quite small. It is fairly dense (30% non-zeros) but even if it was
100% dense I would expect it would take 10MB, not 2GB. At full density, my
guess the memory formula would be something like: 82*5256*12*2 = 10MB:
82=number of rows, 5256=number of columns, 12 = size of double plus size of an
int, 2=doubled the requirements to hold the A matrix to also hold the LU basis
and other things. And, with the simplex algorithm, the LU factorization tends
to be only a bit more dense than the matrix itself, so I would have really
expected memory usage to be around 3 or 4MB. -Marc From: address@hidden
[mailto:address@hidden On Behalf Of Nicholas Farrell Hi all. Model has been successfully generated
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