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Re[2]: [Help-glpk] Solving a large LP problem

From: Andrew Makhorin
Subject: Re[2]: [Help-glpk] Solving a large LP problem
Date: Thu, 15 Jul 2004 20:05:50 +0400

>This is the output I got when I solved with a considerably smaller problem.
>$ glpsol --mps new.mps
>load_mps: reading LP data from `new.mps'...
>load_mps: name `BLANK'
>load_mps: 243742 rows
>load_mps: 364514 columns
>load_mps: 1148311 non-zeros
>load_mps: 1 right-hand side vector(s)
>load_mps: 0 range vector(s)
>load_mps: 0 bound vector(s)
>load_mps: 932145 cards were read
>lpx_simplex: original LP has 243742 rows, 364514 columns, 1148311 non-zeros
>lpx_simplex: presolved LP has 90344 rows, 203072 columns, 487180 non-zeros
>lpx_adv_basis: size of triangular part = 89732
>umalloc: size = 3614184; malloc failed
>Is this b/c I have less system memory available, or b/c of something to 
>do with the code? How can I check if system memory is the problem.

The last message means that some glpk routine attempted to allocate a
memory block of 3,614,184 bytes long, however, the control program
could not satisfy the request (i.e. malloc returned NULL). As a rule
this happens if the machine has not enough ram memory. You can try to
specify the option `--nopresol', because presolver data structures
eat up much ram memory (although for your instance using the presolver
has a significant effect). The error also may happen due to some system
settings which limit the amount of ram memory allocated to application

Btw, glpsol 4.4 is installed on the NEOS Server:
You can try to submit your mps file to the server at least to see
whether glpsol is able to solve your instance.

Andrew Makhorin

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