[Coin-discuss] Problem with row names in ClpModel

[John J Forrest]

Anureet,

The coding in ClpModel could lead to problems and I have changed it but 
that was not the problem here.  There is no efficient way for the code to 
know what names already exist when it adds rows and so you will get two 
rows called R0000007 with your test case.  You could of course drop all 
names at the beginning which would make adding cuts slightly faster and 
then the writeMps would generate names each time.

What I have done is to modify writeMps in CoinMpsIO.cpp so that it will 
check for duplicate names (only of the type Rnnnnnnn or Cnnnnnnn) and 
change them with a message.  With your test case you now get R0000005, 
R0000007, R0000009, R0000008 as the last 4 row names.  That is the best I 
can think of for now.  As a user you could also note the number of 
original rows and then rename any additional cuts left at time of 
writeMps.

John Forrest



Anureet Saxena <anureet at yahoo.com> 
Sent by: coin-discuss-bounces at list.coin-or.org
02/21/2006 09:44 PM
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[Coin-discuss] Problem with row names in ClpModel






hi,
 
I think there is an error in the row (re)naming routines of ClpModel. I am 
using the latest version of Clp, which I downloaded today (Feb 21, 2006).
 
There is a small code with 5 variables and 5 constraints which captures 
this error and is available at 
 
http://www.andrew.cmu.edu/user/anureets/workspace.tgz
 
A README file in the above .tgz directory contains a brief message 
describing the code. In particular, after the following operations the 
test3.mps file generated by the code is corrupted (it has two rows with 
the same name):
 
o 3 cuts added
o 1 cut is removed
o 2 cuts added
 
The bug seems to be related to the following piece of code from 
ClpModel::resize()
--------------------------------------
#ifndef CLP_NO_STD
  if (lengthNames_) {
    // reduce row and column names vectors only if necessary
    if (rowNames_.size() < (unsigned int)numberRows_)
      rowNames_.resize(numberRows_);
    if (columnNames_.size() < (unsigned int)numberColumns_)
      columnNames_.resize(numberColumns_);
  }
#endif
-------------------------------------------------------
 
I guess the row and column names vectors should be resized "always" 
irrespective of whether 
 
"rowNames_.size() < (unsigned int)numberRows_) "
 
or not. I would greatly appreciate any help in this regard.
 
Thanking You,
Anureet Saxena
 
 


Anureet Saxena
anureet at cmu.edu
anureet at yahoo.com

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