Search found 30 matches

by abb.omidi
1 month ago
Forum: Modeling
Topic: Defining the planning horizon in the RCPSP
Replies: 0
Views: 518

Defining the planning horizon in the RCPSP

Dear support team, I am trying to write an optimization model related to the resource-constrained project schedule based on Pritsker et al. formulation. The model is as follows: test.jpg When I have defined the objective function as shown in the model, the final solution is incorrect but, when I wri...
by abb.omidi
2 months ago
Forum: Modeling
Topic: Issue with the reformulating MINLP
Replies: 0
Views: 417

Issue with the reformulating MINLP

Dear support team, I have tried to solve an optimization problem (an MINLP) to minimize the number of items that need to be stored. The objective function is as follows: objective function: Minimize z = sum(i, R(i)/x(i)) Where, R(i), i in {1, ..., n}, given constant and x(i) are integer variables. I...
by abb.omidi
10 months ago
Forum: Modeling
Topic: Solving MIP using MCP
Replies: 0
Views: 723

Solving MIP using MCP

Dear community team, I'm trying to solve a BIP using MCP solver. When I run the problem I have the following issue: Discrete variables can only appear in MIP, RMIP, MINLP, RMINLP, MIQCP or RMIQCP MPEC RMPEC problems. I was wondering if, A) Is it possible to use MCP solver for BIP/MIP? B) I'm trying ...
by abb.omidi
1 year ago
Forum: Modeling
Topic: Implementing decomposition method
Replies: 2
Views: 642

Re: Implementing decomposition method

Dear Dr Bussieck,

Many thanks for your suggestion.
As I'm not any experience in the graph colouring and I am interested in scheduling model, I'm wondering if, are there any related materials for the scheduling problems?

Regards
Omidi
by abb.omidi
1 year ago
Forum: Modeling
Topic: Implementing decomposition method
Replies: 2
Views: 642

Implementing decomposition method

Dear support team, I have often used GAMS and now have tried to implement a Dantzig-Wolfe Decomposition for an LP problem. It works fine for a small instance. Now, I'm trying to extend the DW-based algorithm to solve the MIP model. I'm aware that some of the algorithms like heuristic-based CG, can b...
by abb.omidi
1 year ago
Forum: Modeling
Topic: GAMS Kestrel Issue
Replies: 3
Views: 1413

Re: GAMS Kestrel Issue

Dear Dr Bussieck, Many thanks for your detailed explanations. The issue was fixed and the model was solved by the kestrel. I have another issue and I was wondering if, you could advise me about that. I have tried to solve a scheduling problem and regard to, the model is a large scale, I would like t...
by abb.omidi
1 year ago
Forum: Modeling
Topic: GAMS Kestrel Issue
Replies: 3
Views: 1413

GAMS Kestrel Issue

Dear support team, I tried to use GAMS and Kestrel a while and it worked fine. Recently, I downloaded the new GAMS version (30.1.0 re01a340 WEX-WEI x86 64bit/MS Windows) and I activated it by using a trial licence. Now, I'm trying to solve an optimization model using GAMS/Kestrel. When I run the GAM...
by abb.omidi
1 year ago
Forum: Modeling
Topic: Special constraint formulation
Replies: 0
Views: 1095

Special constraint formulation

Hello community team, I have tried to write a scheduling problem which has been described by Sousa and Wolsey in machine scheduling. I'm going to use two different approaches to write my code. First, using the special syntax into the constraint and second, create dynamic sets. The following code des...
by abb.omidi
1 year ago
Forum: Modeling
Topic: How to execute a warm start using GAMS/Cplex
Replies: 0
Views: 1022

How to execute a warm start using GAMS/Cplex

Dear community team, I have tried to solve a scheduling model. I would like to use a warm start to solve my problem because The model takes much time to solve optimally even for a small set of given data. The model statistic and what I'm looking for are as follows. The original model, a small instan...
by abb.omidi
1 year ago
Forum: Modeling
Topic: GAMS/convert solver
Replies: 2
Views: 1290

Re: GAMS/convert solver

Dear Fred,

Thanks so much for your reply. Would you say, is there any way to get a (.MPS) like format from GAMS, please?

Regards
Abbas