Re: [Help-glpk] Slow performance on "Select minimum" task

[Michael Hennebry]

On Wed, 6 Jun 2018, Jan van Rijn wrote:

> The way I interpreted your solution was that 'at least one y-value per
> column will be >= 1'.
> I don't see exactly which constraint makes sure that there will be exactly
> one y-value per column 1
> (which, again, we don't need if all values in M are >= 0).
You are correct.
The y's have no upper bound, not even one.

> If M contains negative values, it could be that:
> * an ideal solution would have multiple y-values per column bigger than
> zero, and
> * These values will not necessarily be one, but can take even higher values
> (due to this GLPK gave an error message, and this is how I found out)
In the case of negative M's,

Adding SUM y[r,c] = 1
        r

is sufficient.
The y's still do not need to be declared binary.

Being an added constraint, it might speed things up with positive M's.

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