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Re: [Help-glpk] Inputting a large sparse matrix in GLPK data file
From: |
xypron |
Subject: |
Re: [Help-glpk] Inputting a large sparse matrix in GLPK data file |
Date: |
Fri, 24 Oct 2008 22:39:50 -0700 (PDT) |
Hello Rajesh,
when dealing with sparse matrices a good idea is to use sets instead of
parameters. This does not only allow to save memory but often eases
formulating constraints.
set I := 1..8;
set J := 1..8;
set A dimen 3 := { (3, 4, 2), (7, 8, 1) };
var v{i in I, j in J}, >= 0;
minimize sum : sum{i in I, j in J} v[i,j];
s.t. constraint {(i,j,x) in A}:
v[i,j] >= x;
solve;
display v;
end;
When dealing with large data sets consider using a SQL data base and the
table statement.
Best regards
Xypron
Rajesh Kavasseri wrote:
>
> Hello GLPK users,
>
> I am a newbie to GLPK - but am enjoying this !
>
> I need to input (or specify) a large sparse integer matrix A which is
> say 1500 X 1500.
> Only a few entries are integers, say 100 of them are integers and the
> rest are zeros.
> How does one go about inputting this in to GLPK ?
>
> How is this done neatly in GLPK ? (ie initializing all entries of A to
> zero) and inputting only the non-zero ones
> I was trying something along the lines of saying (in the MOD file)
>
> set I := 1..1500;
> set J := 1..1500;
> param A{i in I, j in J}, >=0, default 0.0;
>
> How are the non-zero entries specified then ?
> When I tried setting [in the DAT file]
>
> A[1,2] := 5; A[3, 2]:=9, A[1,6]: = 6;
> I get an error.
>
> Please help !!!
>
>
> Many thanks || Rajesh
>
>
>
>
>
>
> _______________________________________________
> Help-glpk mailing list
> address@hidden
> http://lists.gnu.org/mailman/listinfo/help-glpk
>
>
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