Search found 10 matches

by jgrimm
3 years ago
Forum: Modeling
Topic: Cplex | Setting initial mip solution
Replies: 2
Views: 2076

Re: Cplex | Setting initial mip solution

Please ignore this post and consider it as closed. A preprocessing (tightening) step in gams was causing the problem.
by jgrimm
3 years ago
Forum: Syntax
Topic: issues with gams commands
Replies: 3
Views: 2274

Re: issues with gams commands

Hi Fred,

thanks for your quick reply. Please find the log file attached. Or do you need something different / more?

Kind regards,
Issue1.log
(952 Bytes) Downloaded 222 times
by jgrimm
3 years ago
Forum: Modeling
Topic: Cplex | Setting initial mip solution
Replies: 2
Views: 2076

Cplex | Setting initial mip solution

Hi all, i am facing a problem with setting an initial MIP solution using CPLEX. My variables are as follows: Variables x_ijk(V,V,M) y_ik(V,M) w_ik(V,M) b_ik(V,M) rt_ik(V,M) GOAL; Binary Variable x_ijk, y_ik; Positive Variable b_ik, w_ik, rt_ik; In my understanding by setting mipstart 1 option only b...
by jgrimm
3 years ago
Forum: Syntax
Topic: issues with gams commands
Replies: 3
Views: 2274

issues with gams commands

Hi all, i am facing an unexpected behaviour regarding $call and $csv2gams commands which I am not able to resolve. Execution of statements like $call rmdir /S /Q 20200821_PC results in a errorstate (1, "System cannot find path"). Nevertheless, the command is executed properly (and doing th...
by jgrimm
3 years ago
Forum: Syntax
Topic: Delete files during execution not in compile phase
Replies: 4
Views: 3149

Re: Delete files during execution not in compile phase

Hi all, thanks for the hints and sorry for my late response. It works perfectly! Thank you :) Currently I am facing some kind of other question using BCH facility. I am using userincbcall to identify cuts. So what happens (sample log entries): userincbcall executed: incumbent rejected (-> because pr...
by jgrimm
4 years ago
Forum: Syntax
Topic: Delete files during execution not in compile phase
Replies: 4
Views: 3149

Delete files during execution not in compile phase

Hi all, I am using the usercutcall und userIncbCall functionality by the BCH facility. The logic is as follows: - userincbcall is called once incumbent solution has been determined during branch and bound (/cut) process. This might happen several times in a sequence (i.e. several incumbents are foun...
by jgrimm
4 years ago
Forum: Syntax
Topic: BCH | Cplex | Branch and Cut
Replies: 6
Views: 4407

Re: BCH | Cplex | Branch and Cut

Hi Fred,

perfectly answered. Thank you for your help ! :D

Kind regards,
Jonathan
by jgrimm
4 years ago
Forum: Syntax
Topic: BCH | Cplex | Branch and Cut
Replies: 6
Views: 4407

Re: BCH | Cplex | Branch and Cut

Hi Fred, I was able to implement it on my own. I have done two implementations and seems like both are working properly. First implementation is using BCH facility (usercutcall and userincb). Second implementation is looping over branch & bound solution process several times (and adding cuts aft...
by jgrimm
4 years ago
Forum: Syntax
Topic: BCH | Cplex | Branch and Cut
Replies: 6
Views: 4407

Re: BCH | Cplex | Branch and Cut

Hi Fred, I have been checking the bchtsp.gms before and took some code samples from it. My rework of the code fragments led to the unresolvable issue. It looks much better now. Thank you! In the meantime I have been working on the code and made some more improvements (and fixes). It is running and g...
by jgrimm
4 years ago
Forum: Syntax
Topic: BCH | Cplex | Branch and Cut
Replies: 6
Views: 4407

BCH | Cplex | Branch and Cut

Hi all, currently I am trying to implement an simple branch and cut algorithm using the GAMS Branch & Cut Facility and CPLEX. In a simple implementation a relaxed problem formulation is strengthened in branching process by providing some additional cuts (Problem VRP). A relaxed MIP problem formu...