Search found 11 matches

by lixlz51
1 year ago
Forum: Syntax
Topic: variable ensuring two index are different
Replies: 2
Views: 5145

Re: variable ensuring two index are different

Hi Michael,

You are absolutely a star! I actually need the maximum travel distance for the model as well and your answers are really helpful. Thank you a million and hope you have a wonderful week.

Best regards,
Lina
by lixlz51
1 year ago
Forum: Syntax
Topic: variable ensuring two index are different
Replies: 2
Views: 5145

variable ensuring two index are different

Hi Guys, I am trying to develop a model with one of the decision variable being the following: W(i,j): store i is the closest alternative store for region j; i assume that each customer region has a local store and want to study the customer shopping behavior when their local store is closed - e.g. ...
by lixlz51
1 year ago
Forum: Modeling
Topic: The shortest Route problem
Replies: 1
Views: 819

The shortest Route problem

Hi everyone, As I am new to GAMS and really want to get my head around it for modelling, I tried to compile the examples in the GAMS Studio library myself. I could not really understand the x(i,ip,ipp) in the example given, as I thought the decision variable should be a binary to see whether a certa...
by lixlz51
1 year ago
Forum: Solvers
Topic: Solver didn't provide marginals for model fulfilment
Replies: 6
Views: 2351

Re: Solver didn't provide marginals for model fulfilment

Dear Steve,

Thank you very much indeed for the illustration and explanation! I shall try with the optimality tolerance reduction and see how it goes. Have a good week!

Cheers,
Lina
by lixlz51
1 year ago
Forum: Solvers
Topic: Solver didn't provide marginals for model fulfilment
Replies: 6
Views: 2351

Re: Solver didn't provide marginals for model fulfilment

Hi dirkse,

Thank you so much for the reply. I got a screenshot for the log. I have reduced the the number of stores from 8 to 3 to hopefully understand the mechanism better.
by lixlz51
1 year ago
Forum: Solvers
Topic: Solver didn't provide marginals for model fulfilment
Replies: 6
Views: 2351

Re: Solver didn't provide marginals for model fulfilment

Hi Steve, Thank you for pointing that out for me! I totally forgot to complete my profile. Basically, I have developed a MINLP model for online order fulfilment for my study. I wanted to check the marginal value to see the shadow price for sensitivity analysis. I used ANTIGONE and it gives marginal ...
by lixlz51
1 year ago
Forum: Solvers
Topic: Solver didn't provide marginals for model fulfilment
Replies: 6
Views: 2351

Solver didn't provide marginals for model fulfilment

Hi everyone, I used BARON for my MINLP model (linear constraint but non linear objective function) and the solver report shows normal completion and solver did not provide marginals for model fulfilment. Does it mean the solution is not optimal? If so, how should I solve the problem? Thank you very ...
by lixlz51
2 years ago
Forum: Modeling
Topic: How to compute endogenous cost expressions in GAMs
Replies: 3
Views: 973

Re: How to compute endogenous cost expressions in GAMs

Hi Renger, Thank you very much for your reply. Is there any math function to calculate the calculus expression I posted before? What I did was to compute the calculus and reverse function of the standard normal distribution in Mathematica before I put all those values are known scalar in GAMs. It wo...
by lixlz51
2 years ago
Forum: Modeling
Topic: How to compute endogenous cost expressions in GAMs
Replies: 3
Views: 973

How to compute endogenous cost expressions in GAMs

Capture.PNG Hi everyone, I saw some papers using GAMs to optimize a MINLP model(attached the obj for your consideration in the example of Liu et al (2010)). For the inventory holding cost, the computation is very complex involving calculus, normal distribution and then square root with decision var...
by lixlz51
2 years ago
Forum: Modeling
Topic: Xii >= Xij how to code in GAMS
Replies: 2
Views: 1356

Re: Xii >= Xij how to code in GAMS

Manassaldi wrote:
2 years ago
Hi, it's simple

set i warehouse /1*3/;
alias(i,j);

eq(i,j)$(ord(i) ne ord(j)).. X(i,i) =g= X(i,j);


Bye
Hi Really appreciate your help! Have a good day