Search found 144 matches

by Fred
2 weeks ago
Forum: Syntax
Topic: CEG Model
Replies: 7
Views: 205

Re: CEG Model

Hi, I suggest to run with command line parameter errmsg=1 (https://www.gams.com/latest/docs/UG_GamsCall.html#GAMSAOerrmsg) to reposition compilation error messages in the lst file and then go through you errors step by step by searching for four asterisks (****) in the lst file (they mark an error)....
by Fred
2 weeks ago
Forum: Modeling
Topic: Need help to programm j≠i
Replies: 2
Views: 76

Re: Need help to programm j≠i

Hi, Your code snippet is obviously incomplete and if executed, it does not result in the error you describe. - it does not declare p - the sum() must be assigned to some other symbol - the sum does not control i - not sure what the t in the dollar condition is supposed to do - j<>i is no valid GAMS ...
by Fred
2 weeks ago
Forum: Bugs
Topic: Debugging in GAMS studio
Replies: 2
Views: 232

Re: Debugging in GAMS studio

Hi, No, currently there are no debugging tools integrated in GAMS Studio. The long term development plan incorporates extended debugging facilities but this will take some time. So don't expect anything on short notice (i.e. this year). If you have a particular problem where you are stuck, feel free...
by Fred
2 weeks ago
Forum: Modeling
Topic: Assigning the minimum value of variables
Replies: 2
Views: 104

Re: Assigning the minimum value of variables

Hi, Whether your formulation works depends on how nd(j) contributes to the objective function. You probably declared nd(j) as positive variable (i.e. its lower bound is 0) and minimize it in your objective function. Hence, it is pushed down to zero by the solution algorithm and this does not violate...
by Fred
2 weeks ago
Forum: Modeling
Topic: Considering initial conditions/values in temporal constraints
Replies: 2
Views: 53

Re: Considering initial conditions/values in temporal constraints

Hi, There are many ways to accomplish what you want to do. I'll give you two brief examples, assuming that you have initial temperature value at t=0 stored in a scalar temp_t0. 1. add temp_t0 iff t=1: dtemp(t) .. temp(t)=e=({temp_t0$(sameas(t,'1')+temp(t-1)-A(t)}*exp{-delt*invTau(t)})+A(t) ; 2. let ...
by Fred
2 weeks ago
Forum: Modeling
Topic: How large a MISDP problem can be solved in GAMS?
Replies: 1
Views: 70

Re: How large a MISDP problem can be solved in GAMS?

Hi,

Currently non-of the connected can solve MISDPs. Mosek can solver SDPs (see https://www.gams.com/latest/docs/S_MOSE ... TE_PROGRAM) but not MISDPs.

Regards,
Fred
by Fred
3 weeks ago
Forum: Syntax
Topic: Different definition of Sets and Elements in SOS1 Variables
Replies: 2
Views: 81

Re: Different definition of Sets and Elements in SOS1 Variables

Hi, you would need some dummy set that reperesents a pair (l,w), e.g. *introduce new set lw with card(lw)=card(l)*card(w) and map set elements of lw with pairs of (l,w) $eval cardLW card(l)*card(w) set lw / lw_1*lw_%cardLW% / lw_map(l,w,lw) / (#l.#w):#lw /; *display lw and lw_map (in list format) op...
by Fred
3 weeks ago
Forum: Syntax
Topic: Variable in Conditional Statement
Replies: 1
Views: 132

Re: Variable in Conditional Statement

Hi, This has not so much to do with GAMS but is rather a general question on how to model logical conditions. If you manage to write down the logical condition in a way that fits with e.g. MIP, the implementation in GAMS will be easy. Perhaps you should look into some modeling book (e.g. HP Williams...
by Fred
3 weeks ago
Forum: Solvers
Topic: Initial Function Value too Large
Replies: 1
Views: 122

Re: Initial Function Value too Large

Hi,

The info can probably be found in the lst file (search for ****).

I hope this helps!

Fred
by Fred
3 weeks ago
Forum: Syntax
Topic: matrix error the objective variable has vanished from the model
Replies: 2
Views: 146

Re: matrix error the objective variable has vanished from the model

Hi, Your objective variable theta occurs only once with coefficient pcvar=0. Hence, theta disappears with the current value of pcvar, so GAMS does not know what to optimize. If GAMS would generate this model, the solver could make theta very very negative (model would be unbounded). I hope this help...