Search found 18 matches

by feifan
1 year ago
Forum: Solvers
Topic: CPLEX return integer infeasibility for a feasible MIQP problem
Replies: 3
Views: 1375

Re: CPLEX return integer infeasibility for a feasible MIQP problem

Hi, Michael, Thanks for your answers. I do not get the point regarding the logic of penalties. What does logic of penalties mean? Also, even if I set reduce=1 using the following codes, CPELX still returns integer infeasibility. I hope to get your answers soon. Thanks! $onecho > CPLEX.opt reduce 1 $...
by feifan
1 year ago
Forum: Solvers
Topic: CPLEX return integer infeasibility for a feasible MIQP problem
Replies: 3
Views: 1375

CPLEX return integer infeasibility for a feasible MIQP problem

Dear all, I have built a MIQP model. However, when I use solvers CPELX/CPLEXD to solve it, they return integer infeasibility. I am pretty sure that this model is feasible because if I fix some continuous variables as zero, in my model, I fixed Pr.fx(time) = 0, it returns a feasible solution. Without...
by feifan
1 year ago
Forum: Solvers
Topic: Solvers cannot get a feasible solution for a feasible model
Replies: 0
Views: 1510

Solvers cannot get a feasible solution for a feasible model

Dear All, When I tried to solve a feasible MISOCP model, the solvers cannot return a feasible solution even after 10 hours. The model is feasible for sure because it returns a solution when I fix some variables. I attached my model and data below, could someone help me figure out what was happening?...
by feifan
2 years ago
Forum: Syntax
Topic: why is the elapsed seconds smaller than the total seconds
Replies: 1
Views: 994

why is the elapsed seconds smaller than the total seconds

Dear GAMS users, I was trying to get the time required for solving the model. I got a step summary like this, STEP SUMMARY: 0.000 0.000 STARTUP 0.047 0.047 COMPILATION 0.547 0.547 EXECUTION 0.000 0.000 CLOSEDOWN 0.594 0.594 TOTAL SECONDS 0.593 0.593 ELAPSED SECONDS 5.191 5.191 MAX HEAP SIZE (MB) I r...
by feifan
2 years ago
Forum: Modeling
Topic: Speed up model generation time when using loop
Replies: 3
Views: 1575

Re: Speed up model generation time when using loop

Hi, Fred, Thanks for your answers. In my model, parameters are updated according to the solutions obtained in the last iteration. So, we do not know the parameters in advance. I totally understand what you were referring to. I think the model generation time is acceptable to me because the model is ...
by feifan
2 years ago
Forum: Modeling
Topic: Speed up model generation time when using loop
Replies: 3
Views: 1575

Speed up model generation time when using loop

Hi, all, I am using a loop function to calculate a model with adjustable parameters repeatedly. In each iteration, I change a part of the parameters in the model and solve it again. However, since my model is quite huge, it takes 5-6 seconds to implement model generation. In each iteration, GAMS has...
by feifan
2 years ago
Forum: Modeling
Topic: GAMS/CPLEX return infeasibility while DICOPT give a solution
Replies: 3
Views: 2335

Re: GAMS/CPLEX return infeasibility while DICOPT give a solution

Hi, Fred, thanks for your answers. I use the old version GAMS 24.5.6. Is the infeasibility issue caused by the old version? Unfortunately, I don't have license for the latest GAMS. Then, what am I gonna do? Kind regards, feifan Hi, What version did you use? With the latest GAMS 26.1.0/CPLEXD, Cplex ...
by feifan
2 years ago
Forum: Modeling
Topic: Cplex did not give optimal solution for MISOCP problem after removing a redudant constraint
Replies: 7
Views: 2856

Re: Cplex did not give optimal solution for MISOCP problem after removing a redudant constraint

thank you very much! Michael We got some answer on this. So it turns out to be a Cplex bug which can be easily worked around by setting good bounds to the free variables. Here is the original reply: I found the primary source of trouble, which probably occurred on this model but not previous ones be...
by feifan
2 years ago
Forum: Modeling
Topic: GAMS/CPLEX return infeasibility while DICOPT give a solution
Replies: 3
Views: 2335

GAMS/CPLEX return infeasibility while DICOPT give a solution

Hi, all, My model is a MISOCP problem. When I used GAMS/CPLEXD to solve the model, the solver returned infeasibility. However, when I fixed my binary decision variables as zero and solved it again using CPLEXD, it did give a feasible solution. Especially, the DICOPT solver could give a feasible solu...
by feifan
2 years ago
Forum: Modeling
Topic: Problem with integer infeasiblity
Replies: 1
Views: 991

Problem with integer infeasiblity

Hi, all, In my model, I have three kinds of decision variables, they are Y_l(n1,n2), X_z(zn), and belta(n1,n2); When I define these variables as positive continuous variables and fix them as zero (Y_l.fx=0; X_z.fx=0, and belta.fx=0), I got a obvious solution with all variables being zero. However, w...