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RE: [Help-glpk] Strange Question

From: Welson Sun
Subject: RE: [Help-glpk] Strange Question
Date: Wed, 3 Mar 2004 17:30:00 -0700

Thanks Michael,

Although I am not quite understand what you said, at least I know that do
not use MIP routine to retrieve answer if you are using simplex algorithm.

Regarding the second question, it turns out that it is the problem with the
JNI.dll. I switched to another Glpk JNI dll from a german website, and it
runs perfectly! The real problem with the previous dll is that the memory is
really toasted after you run the simplex algorithm so that you can not
allocate new objects any more................

So, still, I think it is necessary that there needs a make file for
generating JNI dll under Windows, so that we don't need to try out various
DLLs from various people.


-----Original Message-----
From: Michael Hennebry [mailto:address@hidden 
Sent: Wednesday, March 03, 2004 8:45 AM
To: Welson Sun
Cc: address@hidden
Subject: Re: [Help-glpk] Strange Question

On Tue, 2 Mar 2004, Welson Sun wrote:

> Hi all, I have met a strange question with Glpk, can you help me out?
> I am using Glpk in Cygwin under WindowsXP. Since currently there is no 
> Windows makefile for Glpk JNI, I used the precompiled version from 
> address@hidden .
> My LP problem is quite simple:
> Minimize C1X1 + C2X2 + ..... + CnXn
> So that
>     Xi - Xj <= Wij ( 1 <= i,j <= n )
> Where all X are integer and all Wij are non-negtive integer.
> The first strange problem is that I can use simplex() method to solve 
> this, while I cannot use integer() method to solve this, the later will
> GlpkMsg: lpx_integer: optimal solution of LP relaxation required
> I have set the problem to be MIP type, so how can this be possible?

If you RTFM, you will discover that lpx_integer may only follow lpx_simplex.
If, as seems likely, the constraint matrix is totally unimodular, you only
need lpx_simplex anyway.
If you only use lpx_simplex, don't try to fetch an MIP solution.

The other, I can't help you with.

Mike   address@hidden
"Two roads divurged in a woods, and I took the road less travelled by...
and they CANCELLED MY FRIKKIN' SHOW. I totally shoulda took that road
with all those people on it. Damn."                           --  Joss

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