Search found 219 matches

by bussieck
2 hours ago
Forum: Syntax
Topic: finding Hamiltonian Path in TSP
Replies: 1
Views: 8

Re: finding Hamiltonian Path in TSP

Have you looked at the code of the TSP examples in GAMS Model Library? Some of them implement subtour elimination cuts and therefore need to answer exactly your question. See https://www.gams.com/latest/gamslib_ml/ ... ml#gamslib and search for tsp.

-Michael
by bussieck
2 days ago
Forum: Modeling
Topic: Running MIP Models bigger than 250GBs
Replies: 1
Views: 53

Re: Running MIP Models bigger than 250GBs

Hi, Expressing the model in GB is not so helpful. Estimate manually how many variables and constraints your model will have. Also the number of discrete (e.g. binary) variables are good to know. Also try to estimate how many non-zeros you will eventually have. This will also allow you to estimate th...
by bussieck
3 days ago
Forum: Announcements
Topic: GAMS Distribution 26.0.0 (Beta Release)
Replies: 0
Views: 67

GAMS Distribution 26.0.0 (Beta Release)

Hi GAMS Users, We would like to announce the availability of the GAMS Beta Release 26.0.0. Please consult the beta release notes for details about new features and updated solvers: https://www.gams.com/beta/docs/RN_26.html If you are interested in experimenting with this beta release, please downloa...
by bussieck
4 days ago
Forum: Syntax
Topic: Please help me with this model
Replies: 2
Views: 40

Re: Please help me with this model

Seems that some system does not like the spaces in your file name. Newer version of Studio should not have issues with this. I suggest you rename your file to something without spaces.

-Michael
by bussieck
5 days ago
Forum: Modeling
Topic: Execution Error : Division by zero
Replies: 3
Views: 117

Re: Execution Error : Division by zero

GAMS is pretty precise giving you pointers to your problem. In the listing file you find: **** Exec Error at line 188: division by zero (0) line 188 reads 188 augm_obj.. sum(o1,dir(o1)*b(o1)) + 1e-3*sum(om1,sl(om1)/(maxobj(om1) - minobj(om1))) =e= a_objval; Fortunately, there is only one division by...
by bussieck
1 week ago
Forum: Modeling
Topic: Assigning values for mappings
Replies: 1
Views: 72

Re: Assigning values for mappings

The compiler complains with: 5 Parameter C(j) /632.645 1000/; **** $122 $148 **** 122 One dimensional set expected **** 148 Dimension different - The symbol is referenced with more/less **** indices as declared Even though j is two-dimensional, GAMS declaration statements need one-dimensional domain...
by bussieck
1 week ago
Forum: Modeling
Topic: How to use non-binary variable in a conditional statement MILP
Replies: 1
Views: 92

Re: How to use non-binary variable in a conditional statement MILP

Similar questions have been asked before. Search for "logic constraints" or "williams" (that's a name of an author for a book that teaches that). So here only a short answer: A<B => C=1 is equivalent to C=0 => A > B. This we can do with a linear constraint (and binary variable C): A > B - (B-A.lo)*C...
by bussieck
1 week ago
Forum: Syntax
Topic: Syntax error for EMP equilibrium problem
Replies: 2
Views: 137

Re: Syntax error for EMP equilibrium problem

Look at the EMP info file you produce (e.g. do a gamskeep and look into the 225a directory at file empinfo.dat). Line 3 reads: q('a1','j2','n2') q('a1','j3','n2') Ka('a1','n3') theta('a1','n3') R('a1','n3') I('a1','n3') q('a1','j1','n3') q('a1','j2','n3') q('a1','j3','n3') Ka('a1','n4') theta('a1','...
by bussieck
2 weeks ago
Forum: Solvers
Topic: *** Failure calling solver: CONOPT4 (rc=1). What does it mean?
Replies: 5
Views: 206

Re: *** Failure calling solver: CONOPT4 (rc=1). What does it means?

It means that Conopt4 crashed. Conopt4 was introduced with GAMS 24.8 and is still under heavy development as you can see from the release notes (https://www.gams.com/latest/docs/RN_MAIN.html). Every major release came with an update of Conopt4. So you should see if you can reproduce the failure with...
by bussieck
1 month ago
Forum: Announcements
Topic: ORISE Fellowship at EPA
Replies: 0
Views: 870

ORISE Fellowship at EPA

Crossposting from GAMS-L by Andrew Schreiber: Hi folks, We have a research fellowship in the EPA’s National Center for Environmental Economics that may be a good fit for recent Masters or PhD graduates. It is a one year + fellowship where the individual would have an opportunity to work closely with...