Re: [Help-glpk] Operand following / has invalid type

[Andrew Makhorin]

On Wed, 2020-09-09 at 18:17 -0300, yamifag@cock.li wrote:
> Hey,
> 
> I'm trying to make a program that populates a binary matrix keeping
> as 
> many blank lines as possible, e.g.
> 
> > 00|
> > 11|
> > 10|
> 
> instead of
> 
> > 10|
> > 10|
> > 10|
> 
> 
> 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]);
> 
> I made a few tests and some constraints, I'm pretty sure it's not a 
> problem with the sets, the matrix, or a typo.
> If I had to guess I'd say the error is being caused by the nested
> sums, 
> but I couldn't find much on that.
> 
> Can this be fixed in any way?
> Thanks.
> 
> 

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.