Search found 201 matches

by Fred
7 months ago
Forum: Modeling
Topic: Increasing ‘reslim’ but weaker result in a mip solver
Replies: 5
Views: 487

Re: Increasing ‘reslim’ but weaker result in a mip solver

One potential explanation could be that you suffer from non-deterministic behavior when cplex hits the time limit. When you use time limits, the solving process becomes non-deterministic close to the end of the time limit. Eventually, Cplex does "something smart" close to the end with reslim=360 whi...
by Fred
7 months ago
Forum: Modeling
Topic: Increasing ‘reslim’ but weaker result in a mip solver
Replies: 5
Views: 487

Re: Increasing ‘reslim’ but weaker result in a mip solver

Hi,

What about the log files and files required for reproduction?

Fred
by Fred
7 months ago
Forum: Modeling
Topic: Increasing ‘reslim’ but weaker result in a mip solver
Replies: 5
Views: 487

Re: Increasing ‘reslim’ but weaker result in a mip solver

Hi, Assuming that you solve the exact same problem on the exact same hardware with the exact same software and that there are no other computationally expensive jobs running simultaneously, increasing reslim should not lead to a worse solution. You don't say whether you minimze or maximize but from ...
by Fred
8 months ago
Forum: Modeling
Topic: GAMS/convert solver
Replies: 2
Views: 738

Re: GAMS/convert solver

Hi, MPS is a file format for linear problems: https://en.wikipedia.org/wiki/MPS_(format) If you look into the resulting mps file, you should see hints like * Cannot handle NLP [...] * Cannot handle nonlinear equations, nonlinear part ignored. * Cannot handle nonlinear equations, nonlinear part ignor...
by Fred
8 months ago
Forum: Syntax
Topic: Dynamic set allocation with binary variable
Replies: 9
Views: 1415

Re: Dynamic set allocation with binary variable

Hi, you are absolutely right. I edited my post accordingly.

Fred
by Fred
8 months ago
Forum: Syntax
Topic: Dynamic set allocation with binary variable
Replies: 9
Views: 1415

Re: Dynamic set allocation with binary variable

Hi, So you want a constraint that calculates the sum of all distances w(p1,p2) between pixels p1 and p2 on which a house h is built? I think a straightforward (quadratic) formulation could look as follows: equation houseDistNL; positive variable distNL; alias(h,h1,h2), (p,p1,p2); houseDistNL.. distN...
by Fred
8 months ago
Forum: Syntax
Topic: Dynamic set allocation with binary variable
Replies: 9
Views: 1415

Re: Dynamic set allocation with binary variable

Hi, The dynamic set won't help if you need that during the solution process. I guess there are model formulations that do what you want but it is a bit tedious to guess how this could fit into an unknown model. If you share your model and explain where you are struggling to find the right formulatio...
by Fred
8 months ago
Forum: Syntax
Topic: Dynamic set allocation with binary variable
Replies: 9
Views: 1415

Re: Dynamic set allocation with binary variable

Hi, Your syntax is almost corrrect. It only misses the level attribute of the variable (https://www.gams.com/latest/docs/UG_Variables.html#UG_Variables_VariableAttributes) and it seem that h is a set elemnt which means it should be quoted. Also, I suggest not to test for equality (due to tolerances ...
by Fred
8 months ago
Forum: Modeling
Topic: Problem with creating a constraint for a minimum amount of consecutive days
Replies: 1
Views: 290

Re: Problem with creating a constraint for a minimum amount of consecutive days

Hi, I think the following example should do the trick. binary variable y(i,l) 'worker i works on day l'; variable start(i,l) 'value of 1 indicates that worker i starts to work on day l'; equation defStart(i,l) minconsec(i,l); defStart(i,l).. start(i,l) =e= y(i,l) - y(i,l-1); minconsec(i,l)$(ord(l)>1...
by Fred
9 months ago
Forum: Syntax
Topic: Error 66 even when all symbols are defined and assigned... help!
Replies: 2
Views: 481

Re: Error 66 even when all symbols are defined and assigned... help!

Hi, If you look into the listing file, the first error you get is **** $66,256,299 UNEXPECTED END OF FILE (1) **** 3 ERROR(S) 0 WARNING(S) After adding a semicolon after the solve statement yo get 79414 solve MEPI using mip minimizing of; **** $66,256 **** LINE 251 INPUT C:\Users\user\Documents\supp...