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dupcol_action Class Reference

Detect and remove duplicate columns. More...

#include <CoinPresolveDupcol.hpp>

Inheritance diagram for dupcol_action:
Collaboration diagram for dupcol_action:

List of all members.

Classes

struct  action

Public Member Functions

const char * name () const
 A name for debug printing.
void postsolve (CoinPostsolveMatrix *prob) const
 Apply the postsolve transformation for this particular presolve action.
 ~dupcol_action ()

Static Public Member Functions

static const CoinPresolveActionpresolve (CoinPresolveMatrix *prob, const CoinPresolveAction *next)

Detailed Description

Detect and remove duplicate columns.

The general technique is to sum the coefficients a_(*,j) of each column. Columns with identical sums are duplicates. The obvious problem is that, e.g., [1 0 1 0] and [0 1 0 1] both add to 2. To minimize the chances of false positives, the coefficients of each row are multipled by a random number r_i, so that we sum r_i*a_ij.

Candidate columns are checked to confirm they are identical. Where the columns have the same objective coefficient, the two are combined. If the columns have different objective coefficients, complications ensue. In order to remove the duplicate, it must be possible to fix the variable at a bound.

Definition at line 32 of file CoinPresolveDupcol.hpp.


Constructor & Destructor Documentation

dupcol_action::~dupcol_action ( )

Member Function Documentation

const char* dupcol_action::name ( ) const [virtual]

A name for debug printing.

It is expected that the name is not stored in the transform itself.

Implements CoinPresolveAction.

static const CoinPresolveAction* dupcol_action::presolve ( CoinPresolveMatrix prob,
const CoinPresolveAction next 
) [static]
void dupcol_action::postsolve ( CoinPostsolveMatrix prob) const [virtual]

Apply the postsolve transformation for this particular presolve action.

Implements CoinPresolveAction.


The documentation for this class was generated from the following file:
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