CoinUtils
2.10.13
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Detect and remove duplicate columns. More...
#include <CoinPresolveDupcol.hpp>
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const char * | name () const |
A name for debug printing. More... | |
void | postsolve (CoinPostsolveMatrix *prob) const |
Apply the postsolve transformation for this particular presolve action. More... | |
virtual | ~dupcol_action () |
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CoinPresolveAction (const CoinPresolveAction *next) | |
Construct a postsolve object and add it to the transformation list. More... | |
void | setNext (const CoinPresolveAction *nextAction) |
modify next (when building rather than passing) More... | |
virtual | ~CoinPresolveAction () |
Virtual destructor. More... | |
Static Public Member Functions | |
static const CoinPresolveAction * | presolve (CoinPresolveMatrix *prob, const CoinPresolveAction *next) |
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static void | throwCoinError (const char *error, const char *ps_routine) |
Stub routine to throw exceptions. More... | |
Additional Inherited Members | |
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const CoinPresolveAction * | next |
The next presolve transformation. More... | |
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.
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A name for debug printing.
It is expected that the name is not stored in the transform itself.
Implements CoinPresolveAction.
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Apply the postsolve transformation for this particular presolve action.
Implements CoinPresolveAction.