[Coin-lpsolver] problems with BInvCol and BInvRow
John J Forrest
jjforre at us.ibm.com
Fri Sep 16 15:06:22 EDT 2005
Sorry - I was thinking of the tableau methods.
getBInvRow was correct - but did not allow for scaled matrices. getBInvCol
needed some sign changes.
The sign changes were easy - doing scaling was not so easy - hope it is
correct.
I would suspect that not many people have tried these methods and use
tableau methods instead.
John Forrest
John J Forrest/Watson/IBM at IBMUS
Sent by: coin-lpsolver-bounces at list.coin-or.org
09/16/2005 12:47 PM
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coin-lpsolver at list.coin-or.org
Subject
Re: [Coin-lpsolver] problems with BInvCol and BInvRow
Clp stores slacks as -1.0 (i.e. not really slack but row activity). There
is a comment about this in OsiClpsolverInterface but something is
obviously wrong. CglGomory.cpp uses CoinFactorization directly so does
not have this problem.
I will try and look at it this weekend.
John Forrest
Anureet Saxena <anureet at yahoo.com>
Sent by: coin-lpsolver-bounces at list.coin-or.org
09/15/2005 05:34 PM
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[Coin-lpsolver] problems with BInvCol and BInvRow
hi,
There seems to be some trouble with the
OsiSimplexInterface::getBInvCol() and
OsiSimplexInterface::getBInvRow() functions.
In particular, constructing the basis inverse via these two functions
gives
different results (after transposing). Furthermore, the problem is
specifically
in those rows whose corresponding basic variable is a slack variable.
A small example (3 rows and 5 variables) and relevent code can be
downloaded
from the following link:
http://www.andrew.cmu.edu/user/anureets/tmp/
File Name: BInvCol_case.tgz
It will be very nice if someone could point out and/or rectify the error.
On a different note, OsiSimplexInterface has a function:
enableSimplexInterface(bool doingPrimal).
The role of the parameter "doingPrimal" is not adequately described in the
doxygen documentation. Could someone please give some idea as to what this
parameter accomplishes.
regards,
Anureet Saxena
ACO Doctoral Student,
Tepper School of Business,
Carnegie Mellon University.
Anureet Saxena
anureet at cmu.edu
anureet at yahoo.com
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