# dupcol_action Class Reference

Detect and remove duplicate columns. More...

`#include <CoinPresolveDupcol.hpp>`

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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.
virtual | ~dupcol_action ()
## Static Public Member Functions
static const CoinPresolveAction * | presolve (CoinPresolveMatrix *prob, const CoinPresolveAction *next)
## Private Member Functions
| dupcol_action ()
| dupcol_action (const dupcol_action &rhs)
dupcol_action & | operator= (const dupcol_action &rhs)
| dupcol_action (int nactions, const action *actions, const CoinPresolveAction *next)
## Private Attributes
const int | nactions_
const action *const | actions_

## 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 | ( |  | ) | `[private]`

dupcol_action::dupcol_action | ( | const dupcol_action & | rhs | ) | `[private]`

dupcol_action::dupcol_action | ( | int | nactions,
|  | const action * | actions,
|  | const CoinPresolveAction * | next |
| ) |  |  | `[inline, private]`

Definition at line 53 of file CoinPresolveDupcol.hpp.

virtual dupcol_action::~dupcol_action | ( |  | ) | `[virtual]`

## Member Function Documentation

dupcol_action& dupcol_action::operator= | ( | const dupcol_action & | rhs | ) | `[private]`

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.

## Member Data Documentation

const int dupcol_action::nactions_`[private]`

Definition at line 49 of file CoinPresolveDupcol.hpp.

const action* const dupcol_action::actions_`[private]`

Definition at line 51 of file CoinPresolveDupcol.hpp.

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

- /home/coin/svn-release/Alps-1.4.8/CoinUtils/src/CoinPresolveDupcol.hpp