[Help-glpk] Linear programming question

[Marc-Antoine Leroux]

        Hi,
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.

Thanks in advance.
Marc-Antoine

MemMAL_proc.mod
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