Originally posted by: dant

Hi guys,

Need urgent help if anyone is willing to lend assistance here.

I'm developing my model using OPL IDE from my laptop, which only has modest specifications. The plan is to export the model into a .lp file and run it at the office which has CPLEX running on a cluster but not OPL IDE. I've checked the option in Language>Run>Export format>LP format to obtain the .lp file. However, I've been getting insufficient memory errors because the model is quite large now. Based on a scaled down model, the processes that seem to take memory are: CPLEX Solve LP relaxation, CPLEX MIP Optimization and a few others. I've increased the virtual memory to maximum, played with 4G Tuning and checked the memory reduction emphasis in IDE but still getting the same error.

Is there a way of just generating the LP file without actually trying to solve the model? It seems solving the model is taking most of the memory. Is there any other way around this? I just need the lp file really.

Thanks guys. Really hoping for some help.

Cheers.
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Originally posted by: dant

By the way I'm also trying to disable large chunks of the constraints successively. The idea is to build the .lp file in blocks and put them together. No luck so far - still running out of memory even if I try to do one constraint at a time.

Help please....
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Originally posted by: dant

Sorry..forgot to mention one more thing : I've increased the 'memory available for working storage' to 2000...
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Originally posted by: Olivier Binckly

Hello,

You could set both following parameters to export your model without solving:

• turn off the presolve
• set a time limit of 0

This way OPL the solve will immediately stop and your initial model will be exported.

Hope it helps
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Originally posted by: dant

Thanks Olib. Much appreciated. Yes it worked...
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Originally posted by: Maissa

hi everyone,
How can i export the matrix of model A, b & c in Excel file or file .txt?
Please HELP ME SOON
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Originally posted by: HuiD

oilB

How to turn off the presolve exactly?

Thanks
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Originally posted by: SystemAdmin

To turn off presolve:

• add a settings file to your run configuration (.ops file)
• open the settings file and under "Mathematical Programming > Preprocessing", set "limit on the number of presolve passes made" to 0

The documentation says "When this parameter is set to zero, CPLEX does not apply presolve, but other reductions may occur, depending on settings of other parameters and specifics of your model."

Hope this helps
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