Originally posted by: babrooks

I have a question about CPLEX memory usage. I read here(https://www-304.ibm.com/support/docview.wss?uid=swg21399933) that CPLEX memory usage in mb on LPs should be approximately proportional to the number of constraints/1000. However, I'm finding that the memory usage grows much faster than the number of constraints.

In my OPL code, I define the model for integer values of parameters nbids and nvals. I am just counting the number of constraints, and it's nbids^2*(nvals+1)*(2nvals+1)/nvals+nbids*(nvals+1)+nvals^2. When I try to run the code, it uses about 2.8gb with nbids=300 and nvals=2, but when I increase nbids to 500, it uses >50gb (the process gets killed by the server). The number of constraints only increases by about 2.8 times. The number of variables grows at about the same rate.

I'm using the primal dual barrier algorithm, and OPL-CPLEX is run using a C++ driver. The driver just loads the OPL model, solves using barrier, and writes the output to an ASCII file. The driver is run on a single node of a Beowulf cluster with 12 cores, 4gb/core. Have tried setting the

Any ideas for why the memory usage is growing so fast? Is there a better approximation for the amount of memory used by CPLEX?

Thanks.
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Originally posted by: babrooks

Realize I forgot to say, I have tried setting the "conserve memory" parameter, with little effect.
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Originally posted by: SystemAdmin

Does it help to reduce the number of threads?
What is the memory consumption if you use only 1 or 2 threads?
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Originally posted by: babrooks

No, it appears to be unaffected by the number of threads.

Actually, I ssh'd to the node, and 'top' indicates that the amount of memory in use is closer to 20gb. So the rate of growth seems to be correct, but still vastly larger than the # of constraints/1000.
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Originally posted by: SystemAdmin

How does the number of non-zeros in your model grow?
What is the count that CPLEX reports for "Number of nonzeros in lower triangle of A*A'" in the log?
These numbers may give a better approximation to the memory required.
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