[Coin-lpsolver] Using Clp under Neos

[Robin Lougee-Heimer]

These are great questions, and their answers should be used to improve the 
current websites. 
I'm not a NEOS user but I can answer two of them.

>Where is the authoritative specification for MPS format ?
There is none.  The MPS format standard is not "standard". Different LP 
solvers handle somethings differently. 
Here's another reference. 
http://www.mosek.com/download/doc/html/2/toolbox/manual/node10.html   I 
use the IBM OSL manual. 

>I am not sure if Clp is attempting to maximize or minimize the objective.
The default is minimize. 

The NEOS-CLP gurus should be able to help with the other q's,

Robin

----------------------------------------------------------------------------------
Robin Lougee-Heimer
IBM TJ Watson Research Center
1101 Kitchawan Road, Yorktown Heights, NY 10598
ph: 914-945-3032   fax: 914-945-3434 
robinlh at us.ibm.com
http://www.coin-or.org





Math407 Summer05 <m407s05 at u.washington.edu> 
Sent by: coin-lpsolver-bounces at list.coin-or.org
06/08/2005 02:01 PM

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Subject
[Coin-lpsolver] Using Clp under Neos







Introduction:
=============

The support people at Neos have suggest that I contact the Clp help 
directly for my questions below. I am having some trouble understanding 
the input and output to the Neos Clp solver for a linear programming case.
On the web page
                 http://www-neos.mcs.anl.gov/neos/solvers/LP:CLP-MPS/
it states "To solve a linear programming problem using MPS as input, you 
need only submit the MPS file". I was able to find something close to a 
specification of this format in the file
                 
http://www.sbsi-sol-optimize.com/manuals/Minos%20Manual.pdf

Question I:
==========
Where is the authoritative specification for MPS format ?

Still the Clp examples seem to have other commands in the submitted job. 
For
example,
                 BEGIN.PAR
                 primalS
                 sol -
                 END.PAR

                 BEGIN.COMMENT
                 Solve using primal simplex, and print solution value
                 END.COMMENT

It may be that these commands are listed on the web page
                 http://www-neos.mcs.anl.gov/neos/solvers/LP:CLP-MPS/
but there is no documentation there (or link to documentation) describing 
what
the commands do.

Question II:
============
Where are the specifications for these other commands (output the MPS 
input
section) and exactly what they do ?

For example, I am not sure how to get Clp to choose which of the rows 
corresponds to the objective . For another example, I am not sure if Clp 
is attempting to maximize or minimize the objective. (These do not seem to 

be part of the MPS input format but perhaps I am wrong in this.)

Question III:
============
Where are the specifications for the output that Neos e-mails back to and
what it means ?

For example, what does the following mean:
                 Optimal objective 0 - 0 iterations time 0.002, Presolve 
0.00
                 Clp:      0 R1                   20 0
                 1 R2                    0                      0
                 2 R3                   20                      0
                 0 X1                    0                      1
                 1 X2                   20                      0
                 Clp:
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