Re: [Help-glpk] Name assignments to a large number of variables
On Sun, 22 Mar 2015, john tass wrote: I do not care whether the problem is going to be solved in a reasonable amount of time or not. I can wait for a long time. The only thing I do care is to get an answer to my question. So, if you can help me I would appreciate it. The unreasonable time referenced is not a year or even a century. More likely it's a large multiple of the age of the universe. That said, you have other problems before you get that far. An algorithm to name your variables uses pretty much the same kind of logic required to get them into a solver in the first place. If you cannot do that, you will have a hard time entering your problem. -- Michael henne...@web.cs.ndsu.nodak.edu SCSI is NOT magic. There are *fundamental technical reasons* why it is necessary to sacrifice a young goat to your SCSI chain now and then. -- John Woods ___ Help-glpk mailing list Help-glpk@gnu.org https://lists.gnu.org/mailman/listinfo/help-glpk
Re: [Help-glpk] Name assignments to a large number of variables
I would suggest to first prototype the model using the GLPK modeling language.You can experiment with formulations and observe performance of the solver. When translating this into a flat C representation, Inventing a naming scheme is often not extremely difficult, e.g. use something like x_1_2_3_4 which can be assembled or parsed when needed . Erwin Kalvelagen Amsterdam Optimization Modeling Group er...@amsterdamoptimization.com http://amsterdamoptimization.com On Sun, Mar 22, 2015 at 5:35 AM, john tass johnyt...@gmail.com wrote: Good morning to everyone, I have a question which may be too simple to answer. Nevertheless I am not quite sure how to proceed. I intend to use GLPK within an ANSI C application and I want to use the API of GLPK. The model I want to solve is too large as far as its size is concerned, i.e. it contains a large number of decision variables. For instance, I have to use the binary variables Xtcpd, where t, c, p, d are indices, t = 1,...,100, c = 1,...,30, p = 1,...7, d = 1,..,5. So far, the number of Xtcpd variables is obviously 100*30*7*5 = 105000. In addition, I need to use an extra large amount of auxiliary variables, and a large number of constraints. The question is how to create the names of all these variables and the names of all these constraints. Obviously, I can not create all these names in a hard coded fashion. Perhaps I can make use of matrices (?). An if so, how exactly shall I write the code? Any answer will be very appreciated. -- Ioannis X. Tassopoulos ___ Help-glpk mailing list Help-glpk@gnu.org https://lists.gnu.org/mailman/listinfo/help-glpk ___ Help-glpk mailing list Help-glpk@gnu.org https://lists.gnu.org/mailman/listinfo/help-glpk
Re: [Help-glpk] Name assignments to a large number of variables
I do not care whether the problem is going to be solved in a reasonable amount of time or not. I can wait for a long time. The only thing I do care is to get an answer to my question. So, if you can help me I would appreciate it. 2015-03-22 18:22 GMT+02:00 usa usa usact2...@gmail.com: Hi, It seems that your model is mixed interger programming. If it has 100K decision variables, I doubt that this can be solved in a reasonable time. Have you ever solved the same size linear programming models by GLPK ? How about the performance ? Best Regards, On Sun, Mar 22, 2015 at 5:35 AM, john tass johnyt...@gmail.com wrote: Good morning to everyone, I have a question which may be too simple to answer. Nevertheless I am not quite sure how to proceed. I intend to use GLPK within an ANSI C application and I want to use the API of GLPK. The model I want to solve is too large as far as its size is concerned, i.e. it contains a large number of decision variables. For instance, I have to use the binary variables Xtcpd, where t, c, p, d are indices, t = 1,...,100, c = 1,...,30, p = 1,...7, d = 1,..,5. So far, the number of Xtcpd variables is obviously 100*30*7*5 = 105000. In addition, I need to use an extra large amount of auxiliary variables, and a large number of constraints. The question is how to create the names of all these variables and the names of all these constraints. Obviously, I can not create all these names in a hard coded fashion. Perhaps I can make use of matrices (?). An if so, how exactly shall I write the code? Any answer will be very appreciated. -- Ioannis X. Tassopoulos ___ Help-glpk mailing list Help-glpk@gnu.org https://lists.gnu.org/mailman/listinfo/help-glpk -- Ioannis X. Tassopoulos ___ Help-glpk mailing list Help-glpk@gnu.org https://lists.gnu.org/mailman/listinfo/help-glpk
Re: [Help-glpk] Name assignments to a large number of variables
Hi, It seems that your model is mixed interger programming. If it has 100K decision variables, I doubt that this can be solved in a reasonable time. Have you ever solved the same size linear programming models by GLPK ? How about the performance ? Best Regards, On Sun, Mar 22, 2015 at 5:35 AM, john tass johnyt...@gmail.com wrote: Good morning to everyone, I have a question which may be too simple to answer. Nevertheless I am not quite sure how to proceed. I intend to use GLPK within an ANSI C application and I want to use the API of GLPK. The model I want to solve is too large as far as its size is concerned, i.e. it contains a large number of decision variables. For instance, I have to use the binary variables Xtcpd, where t, c, p, d are indices, t = 1,...,100, c = 1,...,30, p = 1,...7, d = 1,..,5. So far, the number of Xtcpd variables is obviously 100*30*7*5 = 105000. In addition, I need to use an extra large amount of auxiliary variables, and a large number of constraints. The question is how to create the names of all these variables and the names of all these constraints. Obviously, I can not create all these names in a hard coded fashion. Perhaps I can make use of matrices (?). An if so, how exactly shall I write the code? Any answer will be very appreciated. -- Ioannis X. Tassopoulos ___ Help-glpk mailing list Help-glpk@gnu.org https://lists.gnu.org/mailman/listinfo/help-glpk ___ Help-glpk mailing list Help-glpk@gnu.org https://lists.gnu.org/mailman/listinfo/help-glpk
