bug in OsiCpx getBInvAcol

[svigerske]

Issue created by migration from Trac.

Original creator: @svigerske

Original creation time: 2008-12-30 17:46:53

Assignee: @mjsaltzman

Version: 0.99

Hi,

I do not understand the following code from OsiCpx::getBInvArow:

  int *ind_bas = new int[nrow];
  getBasics(ind_bas);

  for(int i=0; i<nrow; i++) {
    if(sense[i] == 'G') {
    	int ind_slack = ncol+i;  
      if(ind_bas[i] == ind_slack) {  // slack for row is basic; whole row
                                     // must be flipped
	vec[i] = -vec[i];
      }
    }
  }

I do not see why there should be a correspondence between ind_bas[i] and ncol+i, since i just iterates over the basis.

What seem to work for me is

  int *ind_bas = new int[nrow];
  getBasics(ind_bas);

  for(int i=0; i<nrow; i++)
    if (ind_bas[i] > ncol && sense[ind_bas[i]-ncol] == 'G')
      vec[i] = -vec[i];

That is, the sign of vec[i] is flipped if ind_bas[i] is a slack variable and if the corresponding row (ind_bas[i]-ncol) has sense 'G'.

Best,
Stefan

[svigerske]

Comment by @svigerske created at 2008-12-30 17:49:32

getBinvCol seem to have the same problem

[svigerske]

Comment by @svigerske created at 2009-10-04 10:57:34

fixed in trunk and stable/0.100