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Re: [Bug-glpk] maybe a bug

From: Andrew Makhorin
Subject: Re: [Bug-glpk] maybe a bug
Date: Fri, 9 Jul 2004 18:30:25 +0400

>the glpk I used is glpk-4.2. the problem I meet is as following.
>I use glpk to solve a MIP problem.  when I doubt some constraints may be
> broked, I get the  row value by
>lpx_get_row_info(lpx,I,NULL,&value,NULL).  the result is seemed ok. some
> row value as follow.
>1         9.238577  
>2         100008.696580  
>3         100007.745848  
>4         100006.386690 
>5          10.903077   // I only want to check the first five constrints
> then I calculate the row value myself, and I get the following value:
>1          9.238585
>2           10000 9.196580
>3           10000 7.745845
>4           10000 6.386662
>5           10.400755
> so I find there are some difference in the row value by two mathod.
> I have checked my method, and it is simple and valid, 
>can you explain it and help me. 

If you call lpx_get_row_info/lpx_get_col_info, you obtain solution for
lp relaxation, i.e. where all integrality constraints are ignored. To
obtain solution for mip you need to call lpx_get_mip_row/lpx_get_mip_col.

Andrew Makhorin

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