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## Re: [Help-glpk] multiplication of linear forms not allowed

**From**: |
Andrew Makhorin |

**Subject**: |
Re: [Help-glpk] multiplication of linear forms not allowed |

**Date**: |
Thu, 26 Apr 2007 17:06:01 +0400 |

>* I have a constraint which looks as follows:*
>* concordance{j in X, k in X}: sum{i in N} (w[i] * y[i,j,k]) = c[j,k];*
>* where w,y and c are defined as follows:*
>* param c{j in X, k in X};*
>* var w{i in N} >=0, <=1;*
>* var y{i in N, j in X, k in X} binary;*
>* y is a variable which depends on three dimensions, for each element*
>* of N and each pair of X^2*
>* glpsol stops on this constraint and says:*
>* multiplication of linear forms not allowed*
>* Does anybody know how to overcome this problem?*
var wy{i in N, j in X, k in X}, >= 0;
/* wy[i,j,k] = (if y[i,j,k] = 0 then 0 else w[i]) */
s.t. aaa{i in N, j in X, k in X}: wy[i,j,k] <= y[i,j,k];
s.t. bbb{i in N, j in X, k in X}: wy[i,j,k] <= w[i];
s.t. ccc{i in N, j in X, k in X}: wy[i,j,k] >= w[i] + y[i,j,k] - 1;
concordance{j in X, k in X}: sum{i in N} wy[i,j,k] = c[j,k];