Re: Multi problems in GMPL

[Domingo Alvarez Duarte]

Hello !

Meanwhile I implemented only the parsing/display of problem statement 
like ampl but without domains.

https://github.com/mingodad/GLPK/blob/local-set-param/examples/cut2.mod

Output:

====

./glpsol --genonly  -m cut2.mod
>./glpsol --genonly  -m cut2.mod
GLPSOL: GLPK LP/MIP Solver, v4.65
Parameter(s) specified in the command line:
 --genonly -m cut2.mod
Reading model section from cut2.mod...
Reading data section from cut2.mod...
107 lines were read
Checking (line 14)...
Generating Number...
Generating Fill...
Generating Reduced_Cost...
Generating Width_Limit...
Display statement at line 39
problem Cutting_Opt: Cut, Number, Fill;
problem Pattern_Gen: Use, Reduced_Cost, Width_Limit;
problem Mix: Cut, Reduced_Cost;
Model has been successfully generated
>Exit code: 0

====

Cheers !

On 26/8/20 19:57, Domingo Alvarez Duarte wrote:
> Hello !
>
> Thinking in how to have multiple problem in GMPL I'm asking for other 
> user opinions about how that could be expressed, one example can be 
> like the one bellow where we have common elements and namespaced 
> problems.
>
> If you have any other idea that you want to share let me know !
>
> ====
>
> param roll_width;
> set WIDTHS;
>
> problem Cutting_Opt {
>     # ----------------------------------------
>     param nPAT integer >= 0, default 0;
>     set PATTERNS := 1..nPAT;
>     param orders {WIDTHS} > 0;
>     param nbr {WIDTHS,PATTERNS} integer >= 0;
>
>     check {j in PATTERNS}: sum {i in WIDTHS} i * nbr[i,j] <= roll_width;
>
>     var Cut {PATTERNS} integer >= 0;
>
>     minimize Number: sum {j in PATTERNS} Cut[j];
>
>     subject to Fill {i in WIDTHS}:
>        sum {j in PATTERNS} nbr[i,j] * Cut[j] >= orders[i];
> }
>
> problem Pattern_Gen {
>     # ----------------------------------------
>     param price {WIDTHS} default 0;
>
>     var Use {WIDTHS} integer >= 0;
>
>     minimize Reduced_Cost:
>        1 - sum {i in WIDTHS} price[i] * Use[i];
>
>     subject to Width_Limit:
>        sum {i in WIDTHS} i * Use[i] <= roll_width;
> }
> solve Cutting_Opt;
> solve Pattern_Gen;
>
> ====
>
> Cheers !