gams-math | 易学教程

Using GAMS/CPLEX from Python PYOMO

阅读更多关于 Using GAMS/CPLEX from Python PYOMO

问题 I noticed that Pyomo 5.3 offers a GAMS solver plugin. https://github.com/Pyomo/pyomo/blob/master/pyomo/solvers/plugins/solvers/GAMS.py This is very exciting, as we have a GAMS/CPLEX license where we can use CPLEX as solver, but only via GAMS. With the new Pyomo-Gams interface, it should from my understanding be possible to formulate a problem in Pyomo, and have it translated to GAMS and solved by CPLEX. However, when I test this with the shell integration, it is very slow (40s for 30 solves

Use variable in GAMS dollar

阅读更多关于 Use variable in GAMS dollar

I have a GAMS code where I want an if statement. I've read about dollar condition and I thought it could help me. Reading GAMS user guide , it says: The Dollar Condition This section introduces the dollar operator , which is one of the most powerful features of GAMS. The dollar operator operates with a logical condition. The term $(condition) can be read as 'such that condition is valid' where condition is a logical condition. Attention: The dollar logical conditions cannot contain variables. Variable attributes (like .l and .m) are permitted however. The dollar operator is used to model

Use variable in GAMS dollar

阅读更多关于 Use variable in GAMS dollar

问题 I have a GAMS code where I want an if statement. I've read about dollar condition and I thought it could help me. Reading GAMS user guide, it says: The Dollar Condition This section introduces the dollar operator , which is one of the most powerful features of GAMS. The dollar operator operates with a logical condition. The term $(condition) can be read as 'such that condition is valid' where condition is a logical condition. Attention: The dollar logical conditions cannot contain variables.

How can define Union, intersection, symmetric difference?

阅读更多关于 How can define Union, intersection, symmetric difference?

问题 I have set i ,j and sub set k from i and j . I want to have union , intersection and symmetric difference . The size of my set is large. But to clarify the question , let's I=1*3, j=6*12 . Set i /1*3/ j/6*12/ K(i ,j) 1.(6,9,11) 2.(7,11) 3.(8,9,10,12) ; I want to have Union, intersection, and symmetric difference on k(i ,j). For example for k(1,j) and k(2,j). Intersection is '11' and symmetric difference is '6,7,9' and Union is '6,7,9,11' I have to calculate intersection, Union , and symmetric

How can define Union, intersection, symmetric difference?

阅读更多关于 How can define Union, intersection, symmetric difference?

I have set i ,j and sub set k from i and j . I want to have union , intersection and symmetric difference . The size of my set is large. But to clarify the question , let's I=1*3, j=6*12 . Set i /1*3/ j/6*12/ K(i ,j) 1.(6,9,11) 2.(7,11) 3.(8,9,10,12) ; I want to have Union, intersection, and symmetric difference on k(i ,j). For example for k(1,j) and k(2,j). Intersection is '11' and symmetric difference is '6,7,9' and Union is '6,7,9,11' I have to calculate intersection, Union , and symmetric difference for all possible combination in k( i ,j) , how can I do this in GAMS ? How can i code it? I

Comparison of GAMS versus AMPL Algebraic Modelling Languages

阅读更多关于 Comparison of GAMS versus AMPL Algebraic Modelling Languages

问题 I'd be interested in getting the opinion from users of GAMS and AMPL on what the strength and weaknesses of each these languages are. 回答1: In terms of functionality they are pretty much the same allowing to express most types of optimization problems. Personally, I prefer AMPL because it has intuitive and expressive syntax and it is very well documented in the book. Another important advantage of AMPL is that despite the fact that it is commercial you can avoid the vendor lock-in because

Comparison of GAMS versus AMPL Algebraic Modelling Languages

阅读更多关于 Comparison of GAMS versus AMPL Algebraic Modelling Languages

I'd be interested in getting the opinion from users of GAMS and AMPL on what the strength and weaknesses of each these languages are. In terms of functionality they are pretty much the same allowing to express most types of optimization problems. Personally, I prefer AMPL because it has intuitive and expressive syntax and it is very well documented in the book . Another important advantage of AMPL is that despite the fact that it is commercial you can avoid the vendor lock-in because there is an open source alternative - GNU MathProg . GAMS on the other hand used to have a more advanced IDE

initialize decision variables in GAMS in form of a set + equation gives errors

阅读更多关于 initialize decision variables in GAMS in form of a set + equation gives errors

问题 I am trying to model a problem using GAMS. I have 2 questions: 1) How to initialize the decesion value P? it supose to be in the following form P(I)/ i1 25 i2 33 / 2) I am trying to calculate SINR as in SINR(I) =e= hh(I)*P(I) / sqr(sigma)+sum(I,H(J,I)*P(I)); However, I got always an erro either the set is already controller or domain isssues. How can I solve this problem? Part of the CODE set I number of users /i1,i2/ J users to interfer with /j1,j2/ iteration number of iterations /1/ ;

Best practice for cross-platform file system manipulations in GAMS

阅读更多关于 Best practice for cross-platform file system manipulations in GAMS

I would like to manipulate the file system from some GAMS code. I am coming to this project mid-stream, and as a GAMS newbie, but am used to writing cross-platform file manipulations in other languages. It would be good for this code to be cross-platform Linux and Windows. Right now there is a commented-out line *$call 'mkdir "%runfolder%"' that I would like to un-comment (enable), however, I am having a hard time finding documentation on whether this would work cross-platform (I suspect not), and if not, how I could do this in a cross-platform way. How can I manipulate the file system in a

Best practice for cross-platform file system manipulations in GAMS

阅读更多关于 Best practice for cross-platform file system manipulations in GAMS

问题 I would like to manipulate the file system from some GAMS code. I am coming to this project mid-stream, and as a GAMS newbie, but am used to writing cross-platform file manipulations in other languages. It would be good for this code to be cross-platform Linux and Windows. Right now there is a commented-out line *$call 'mkdir "%runfolder%"' that I would like to un-comment (enable), however, I am having a hard time finding documentation on whether this would work cross-platform (I suspect not)