On Tue, Feb 07, 2012 at 10:54:47PM +0100, Daniel Seither wrote:
> Hi,
>
> in package optim, function linprog(), there is an error that prevents
> proper execution of the function if only the minimal set of parameters
> (f, A, b) is given.
>
> Example code to reproduce:
>
> f = [-3, -2, -2]';
> A = [ 1, 0, 1;
> 1, 1, 0;
> 1, 2, 0];
> b = [8, 7, 12]';
> linprog(f, A, b)
>
> This leads to the following error message:
>
> > error: size (lb) != [(rows (f)) 1]
> > error: called from:
> > error: /usr/share/octave/packages/3.2/optim-1.0.16/linprog.m at line 99,
> > column 7
> > error: test.m at line 6, column 1
>
> I use Octave 3.2.4 that comes with the latest stable version of Ubuntu
> (11.10) and the octave-optim packet version 1.0.16-1 from the official
> Ubuntu repositories.
>
> The relevant code in linprog.m is the following:
> > ## Sanitize lb
> > if (isempty (lb))
> > LB = - Inf (nr_f, 1);
> > endif
> > if (size (lb) != [nr_f 1])
> > error ("size (lb) != [(rows (f)) 1]");
> > endif
> >
> > ## Sanitize ub
> > if (isempty (ub))
> > UB = Inf (nr_f, 1);
> > endif
> > if (size (ub) != [nr_f 1])
> > error ("size (ub) != [(rows (f)) 1]");
> > endif
>
> If lb is empty, it is not changed but a new variable LB is set. The
> following condition can thus never be fulfilled when lb was initially
> empty. For ub/UB, the same holds. If LB and UB are replaced by their
> lowercase equivalents, the code works as expected.
>
> Greetings and thanks for your work on Octave,
> Daniel
I applied your fix to SVN, thanks. BTW linprog seems to be only a
wrapper to glpk, to mimick Matlabw linprog, without quite achieving
compatibility.
Olaf
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