Re: Help with slow model translation
On 2/21/20 6:26 PM, Heinrich Schuchardt wrote: On 2/21/20 5:46 PM, Greg Gruber wrote: Hello, I have a model that I have developed using MathProg, that I am using regularly. Some problem datasets result in very large models. The problem itself is solving very quickly, but I am finding the model translation (reading the .mod file, data files, and setting up the problem) to be very slow. I came across this on the wikipedia entry: " The take-home message is that nested set iterations should be avoided where possible, as these greatly expand the dimensionality and size of the model space to be processed.", and it discusses a case on the OSeMOSYS energy model where the execution time was reduced from 15 hours to 9 minutes by a reformulation. Unfortunately, I'm not sure what they mean here, and I am looking for an example. I have tried searching the OSeMOSYS site for more information, as well as searching for publications by Jonas Horsch, who did the reformulation, but have had no luck yet. Does anybody have examples illustrating how to avoid nested-set iterations in MathProg? Thanks in advance, Greg Hello Greg, please, provide an example model which shall be simplified. Best regards Heinrich Thanks for the example model. Using the GMPL language is not very efficient to formulate the complex constraints you have. For creating the problem formulation for very large problems I would always prefer using a programming language like Java to generate the model formulation and directly call the solver library from the programming language. Your problem has more than 30 million variables. I doubt that you will get a solution for this size of a problem with GLPK. Best regards Heinrich
Re: Help with slow model translation
On 2/21/20 5:46 PM, Greg Gruber wrote: Hello, I have a model that I have developed using MathProg, that I am using regularly. Some problem datasets result in very large models. The problem itself is solving very quickly, but I am finding the model translation (reading the .mod file, data files, and setting up the problem) to be very slow. I came across this on the wikipedia entry: " The take-home message is that nested set iterations should be avoided where possible, as these greatly expand the dimensionality and size of the model space to be processed.", and it discusses a case on the OSeMOSYS energy model where the execution time was reduced from 15 hours to 9 minutes by a reformulation. Unfortunately, I'm not sure what they mean here, and I am looking for an example. I have tried searching the OSeMOSYS site for more information, as well as searching for publications by Jonas Horsch, who did the reformulation, but have had no luck yet. Does anybody have examples illustrating how to avoid nested-set iterations in MathProg? Thanks in advance, Greg Hello Greg, please, provide an example model which shall be simplified. Best regards Heinrich
Help with slow model translation
Hello, I have a model that I have developed using MathProg, that I am using regularly. Some problem datasets result in very large models. The problem itself is solving very quickly, but I am finding the model translation (reading the .mod file, data files, and setting up the problem) to be very slow. I came across this on the wikipedia entry: " The take-home message is that nested set iterations should be avoided where possible, as these greatly expand the dimensionality and size of the model space to be processed.", and it discusses a case on the OSeMOSYS energy model where the execution time was reduced from 15 hours to 9 minutes by a reformulation. Unfortunately, I'm not sure what they mean here, and I am looking for an example. I have tried searching the OSeMOSYS site for more information, as well as searching for publications by Jonas Horsch, who did the reformulation, but have had no luck yet. Does anybody have examples illustrating how to avoid nested-set iterations in MathProg? Thanks in advance, Greg
