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Re: [Help-glpk] solve, add rows, resolve

From: Brady Hunsaker
Subject: Re: [Help-glpk] solve, add rows, resolve
Date: Wed, 17 May 2006 07:47:00 +0400

Andrew Makhorin wrote:
>> - Do you want me to create a small test case to demonstrate the issue?
> Yes, please do that and post it to me. I will reply to your questions
> a bit later, maybe tomorrow.
> Andrew Makhorin


My apologies.  It is not add_rows, but del_cols that is an issue.  I 
wrote the previous email from memory, which was incorrect.

I am attaching a test case.  If we remove the first column of p0033, 
then re-solving fails.  However, if you remove the second column, it 
succeeds.  You can check this by changing the index to be removed.

Presumably the first column is basic in the original solution and the 
second column is non-basic.

My question is this:
- If a basic column is removed, what behavior do you expect from GLPK? 
Should it adjust the basis and resolve?  Resolve starting from the 
beginning (a new basis)?  Fail?


Brady Hunsaker
Assistant Professor
Industrial Engineering
University of Pittsburgh

Attachment: resolve.c
Description: Text Data

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