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Re: Multi problems in GMPL

From: Domingo Alvarez Duarte
Subject: Re: Multi problems in GMPL
Date: Thu, 27 Aug 2020 00:01:30 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0

Hello !

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



./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;

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 !

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