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

[Meketon, Marc]

Xypron used "M" as a large constant (e.g., 9999).  Not as a binary variable.

 

param M := 9999;

var B{J,K} >= 0;

 

s.t. a{j in J}: -M*sum{k in  K}B[j,k] <= A[j] <= M*sum{k in K}B[j,k];

 

-----Original Message-----
From: help-glpk-bounces+address@hidden [mailto:help-glpk-bounces+address@hidden On Behalf Of Reginald Beardsley
Sent: Sunday, October 21, 2012 10:46 AM
To: glpk
Subject: [Help-glpk] "multiplication of linear forms not allowed"

 

 

I'm trying to apply the following constraint following a suggestion by xypron:

 

var M{J} ,binary;

var B{J,K} ,>= 0;

 

s.t. a{j}: -M[j]*sum{k in  K}B[j,k] <= A[j] <= M[j]*sum{k in K}B[j,k];

 

The goal being to force A[j] = 0 if the sum over k of B[j,k] = 0;

 

glpsol 4.47 exits w/ the message in the subject line.  I found Steglich's post of last month, but am having trouble w/ translating the notation in the CMPL 1.7.0 manual to GMPL.

 

From context, I'm guessing that overbar indicates the maximum and underbar the minimum, but I can find nothing to confirm that. The first equation in section 8.3.1 appears to have a typo as there is no underbar in the range specification.  Even if I assume the typo, and explicitly specify the additional variables and  constraints, I still get the subject line message.  Just at a different point.

 

Is it possible to do this in GMPL?  If so, how?

At the moment, the only option I can see would be to make an initial solution w/o the constraint and then recast the problem and solve again.

 

Thanks,

Reg

 

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