Originally posted by: Steffen_84

Hi,

I have cplex_studio125.win-x86-64 installed and I am working with the excel add-in. This works well on one CPU, but takes a lot of time. I therefore tried to start a parallel optimization on a multiprocessor system by setting threads=64 in advanced parameters. Unfortunately this doesn't work.
Does anybody know a solution?

Best regards

Steffen

What exactly does "doesn't" work mean?

Originally posted by: Steffen_84

Thank you for your reply!

CPLEX still runs on one single CPU. I would like to know which parameters I have to change (working with the excel add-in) in order to get to a parallel optimization that is possibly faster. The problem has about 20 000 variables and 1 000 constraints.

How exactly did you specify the threads parameter? Could you show a screen shot of the advanced parameter list? Can you please also try to give 1067 (the parameter's number) as parameter name in the dialog?

Did the solve actually start or may it be that CPLEX just takes a long time to build up the model? To check this you can check the "export model" box on the advanced parameter tab and specify a model file (preferably with extension .sav). That file is written immediately before CPLEX starts to actually optimize your problem.

You can also use that model file and load it into the interactive optimizer (cplex.exe) and analyze solver performance in the interactive optimizer (or even use the tuning tool).

Originally posted by: Steffen_84

Hi,

see the attached screenshot. I also tried usind the parameters number.

It took about 10 mins to write the model file and only a few seconds more until the solution came up. So, according to you explanations, it took 10 mins to build up the model. Is there a way I can build up the model faster?

Thanks!

Your settings look good and according to what you report the issue is indeed in building the model.

What can be done about that depends on how your model is formulated. Can you please take a look at the modeling tips in the user manual and see if this helps? If possible, you should avoid using any Excel function that is not explicitly supported by CPLEX.

Originally posted by: Steffen_84

I only use SUM and SUMPRODUCT. And I think I followed all the modeling tips. I attached the model. Thanks again!