Re: [Help-glpk] Linear programming question

[Andrew Makhorin]

> I have a question not directly linked to GLPK but more to linear programming.
> For my end-year report, I try to do an optimisation of a production process.
> In some cases, the procurement are available in batches of constant size.
> In other words, the quantity to be procured has to be a multiple of
> the given batch size.
> With this equation my model isn't linear anymore:
> s.t. BatchSize{a in N,j in 1..m}: proclevel[a,j] mod ProcBatchSize[a] = 0;
> Could someone help me to find a solution for this constraint or to
> find information
> on this kind of problems?
> I join the rest of my model.

Probably something like this:

var z[a in ..., j in ...], integer, >= 0, <= ... ;

s.t. BatchSize{a in N,j in 1..m}: proclevel[a,j] = z[a,j] * ProcBatchSize[a];

(This assumes, of course, that the batch size is a known constant, not
a variable.)