Re: [Help-glpk] Proper syntax for the Uniform function in the data segment

[Andrew Makhorin]

On Wed, 2013-10-09 at 15:32 -0400, Marc Goetschalckx wrote:
> 
> On 09-Oct-13 7:55 AM, Andrew Makhorin wrote:
> >> I am trying to use the Uniform function to set the value of a
> >> two-dimensional array in the data segment of a model.
> >> Parameter array is defined as follows (and works correctly when used
> >> with explicit value initialization) in the model section
> >>
> >> param c{i in I, j in J},>= 0;
> >>
> >> The following statement gives a syntax error
> >>
> >> param c : Uniform (1, 500);
> >>
> >> I could not find an example of using the Uniform function with a
> >> parameter matrix in the GMPL manual.
> >> What is the proper syntax
> >>
> >>      
> > param c{i in I, j in J},>= 0, := Uniform (1, 500);
> >
> >    
> 
> The following statement in the data section
> 
> param c{i in I, j in J} := uniform (1, 500);
> 
> generates the following syntax error
> 
> data_file.dat, line 131 (offset 1391):
>          expected ; ( [ : or symbol
> context:  param c >>> { <<< i in I, j in J} := uniform (1, 500);
> 
> The initialization of the parameter c with values is part of the data 
> section and instance dependent.  The model section remains unchanged for 
> all instances.
> 

I meant model section. In data section you cannot do that. If you need
to initialize c by randoms only if no data for c are provided in the
data section, you could use 'default' attribute rather than ':=', e.g.

param c{i in I, j in J}, default uniform (1, 500);