Search found 618 matches

by bussieck
1 day ago
Forum: Solvers
Topic: How can I find the global optimal solution for the following MINLP problem.
Replies: 1
Views: 75

Re: How can I find the global optimal solution for the following MINLP problem.

It's a shame that you don't have other MINLP solvers available. For example, BARON solves this in no time: Iteration Open nodes Time (s) Lower bound Upper bound * 1 1 5.06 5093.56 5139.88 1 1 6.38 5093.56 5095.02 5 0 10.77 5093.56 5094.07 Calculating duals *** Normal completion *** Wall clock time: ...
by bussieck
2 days ago
Forum: Tools
Topic: Not to create lst file
Replies: 2
Views: 114

Re: Not to create lst file

On the OS level you can redirect the listing file to the nullfile via command line option o=/dev/null (Unix) or o=nul (Windows), but it is much better to deselect the parts that make the listing file big because with the OS solution GAMS still spends time writing. The table https://www.gams.com/35/d...
by bussieck
3 days ago
Forum: Tools
Topic: Licensing and technical aspects of running GAMS by multiple users
Replies: 1
Views: 71

Re: Licensing and technical aspects of running GAMS by multiple users

GAMS runs concurrently for different users with a single installation just fine (Windows and other OS). Users can customize their GAMS environment (e.g. their default solvers) by using a gamsconfig.yaml (see https://www.gams.com/latest/docs/UG_GamsCall.html#UG_GamsCall_GAMSConfigYAML) location in so...
by bussieck
6 days ago
Forum: Syntax
Topic: Different errors to solve
Replies: 2
Views: 91

Re: Different errors to solve

The gms code and the lst do not match. I worked off the gms code. There were some syntax errors (better quote text with '/', too many closing parenthesis, other minor stuff) but the main issue was uninitialized variable level. You should read about the importance of a starting point for local NLP so...
by bussieck
6 days ago
Forum: Tools
Topic: Access Excel file error
Replies: 1
Views: 841

Re: Access Excel file error

This happens when a) Excel has the file open (this can be a crashed Excel) so if the problem disappears after a reboot check the next time for abbandoned Excel processes in your task manager or b) you have not activated MS Office/Excel (see https://support.microsoft.com/en-us/office/activate-office-...
by bussieck
2 weeks ago
Forum: Announcements
Topic: GAMS Distribution 36.0.0 (Beta Release)
Replies: 0
Views: 87

GAMS Distribution 36.0.0 (Beta Release)

Hi GAMS Users, We would like to announce the availability of the GAMS Beta Release 36.0.0. Please consult the beta release notes for details about new features and updated solvers: https://www.gams.com/beta/docs/RN_36.html If you are interested in experimenting with this beta release, please downloa...
by bussieck
3 weeks ago
Forum: Modeling
Topic: How to solve the nonlinear Weymouth equation in GAMS?
Replies: 1
Views: 118

Re: How to solve the nonlinear Weymouth equation in GAMS?

You can model sgn like this:

Code: Select all

binary variable b(m,n);
equation defb(m,n),deff(m,n);
defb(m,n).. p(m) =g= p(n) - (1-b(m,n))*bigM;
deff(m,n).. f(m,n) =e= (2*b(m,n)-1)*C(m,n)*sqrt(abs(sqr(p(m) - sqr(p(n))));
where bigM is a an upper bound on the variable p.

-Michael
by bussieck
3 weeks ago
Forum: Solvers
Topic: gams to lindo
Replies: 3
Views: 176

Re: gams to lindo

I don't understand your question. -Michael
by bussieck
3 weeks ago
Forum: Solvers
Topic: ANTIGONE initialisation
Replies: 4
Views: 155

Re: ANTIGONE initialisation

No. It does not matter where the initial values come from. In your example you use "SOLVE WATER using NLP" and "SOLVE WATER using MINLP" that only works if you have no discrete variables in your model (and then solving it as MINLP is pointless). If you have discrete variables in model WATER and try ...