Re: [Help-glpk] "The conflict graph is either empty or too big"

[Michael Hennebry]

On Tue, 22 May 2012, spiritfire wrote:

> By doing some researches I found out that my code is doing fine but the
> problem is hard to solve.
>
> I would like to fasten the solver by reducing the precision from 9 to 7
> digits. Is it possible ? Or by reducing the number of iterations but I do
> not know how to do either one of these.

Reducing iterations will certainly not work:
You have yet to get a solution with the iterations you have.

Going from double to single precsion would
not be helpful on any Intel or AMD device.
All floating point arithmetic is done in at least double precision.
I'm not sure there are any devices on which you would get a speed up.

At better tactic might be to use problem-specific information
to generate either constraints or solutions.

Also, suppose one has a zero-one problem and for the current "solution" x:

0<=x<=1

 SUM x[j] + SUM (1-x[j])  < 1
 j in S     j in T

and there is no feasible solution with
x[j]=0 for j in S and x[j]=1 for j in T.

In that case SUM x[j] + SUM (1-x[j]) >= 1 is a valid cut
             j in S     j in T

--
Michael   address@hidden
"On Monday, I'm gonna have to tell my kindergarten class,
whom I teach not to run with scissors,
that my fiance ran me through with a broadsword."  --  Lily