Re: [Help-glpk] Re: Why I get different results when I run lpx_std_basis before simplex?

[Michael Hennebry]

On Tue, 13 May 2008, Xie Zhengwei wrote:

> This script tried to get max and min of every variable.
>
> no $lp->std_basis output
> 1    0.727273    0.000000
> 2    1.000000    0.000000
> 3    1.000000    0.000000
> 4    1.000000    0.000000
> 5    0.000000    0.000000
> 6    0.000000    -1.000000
> 7    1.916667    0.000000
> 8    3.000000    0.000000
> 9    8.000000    0.000000
> 10    3.000000    0.000000
> 11    8.000000    8.000000
> 12    -21.000000    -21.000000
> 13    4.500000    0.000000
>
> with $lp->std_basis output
>
> 1    0.000000    0.000000
> 2    1.000000    0.000000
> 3    1.000000    0.000000
> 4    1.000000    0.000000
> 5    0.000000    0.000000
> 6    0.000000    0.000000
> 7    0.000000    0.000000
> 8    0.000000    0.000000
> 9    0.000000    0.000000
> 10    0.000000    0.000000
> 11    8.000000    0.000000
> 12    0.000000    0.000000
> 13    0.000000    0.000000

It's possible that you gave it a hard problem.
How big are your reduced costs?
What constraints are tight?

-- 
Michael   address@hidden
"Those parts of the system that you can hit with a hammer (not advised)
are called Hardware;  those program instructions that you can only
curse at are called Software."