Re: Operand following / has invalid type

On Thu, 10 Sep 2020, Andrew Makhorin wrote:

> On Wed, 2020-09-09 at 18:17 -0300, [email protected] wrote:

>> I'm trying to make a program that populates a binary matrix keeping
>> as 
>> many blank lines as possible, e.g.

Add another variable for each row in the binary matrix:
z[row]>=m[row, col]
minimize its sum.
The z's need not be binary.

It can be done with a single z,
but I expect user-defined cuts would be necessary.
Note that GLPK assumes cuts are not mathematically necessary.
GLPK might return a solution you deem infeasible.
In that case, you would neeed to add a cut and rerun.
Keeping the previously discovered cuts would not be automatic.

>> Since I know the sum of the lines won't be too big I decided to use
>> an 
>> approach based on division, but I'm getting a "operand following /
>> has 
>> invalid type" error.
>>
>> /* binary matrix */
>> var m{x in X, y in Y} binary;
>> /* minimizes total (sum of line)^-1, a full line is better than two 
>> half-full lines*/
>> minimize maxEmpty: sum{x in X} 1/(1 + sum{y in Y} m[x,y]);

This can be done, sort of.
Again you would need an auxillary variable for each matrix row.
I expect the additional constraints
could be inserted with the original set.

Again it coulod be done with a single z
and the same complications are before.

> In constraints and objectives you can divide only by a constant
> expression. In your case you divide by a linear form that leads to a
> non-linear objective function, which is not allowed. Probably you need
> to reformulate your model.

-- 
Michael   [email protected]
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