C++ Reference: class ZeroHalfCutHelper

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Heuristic to find a good sums of rows from the LP (with coeff -1, +1) that can lead to a violated zero-half cut (i.e. after integer rounding with a divisor 2).

For this, all that matter is the parity of the coefficients and the rhs in the linear combination of the original problem constraint. So this class maintain a copy of the LP matrix modulo 2 on which simplification and heuristic are performed to find good cut candidates(s).

Most of what is done here is described in the paper "Algorithms to Separate {0, 1/2}-Chvátal-Gomory Cuts", Arie M. C. A. Koster, Adrian Zymolka, Manuel Kutschka.

Method
AddBinaryRow	Return type: void Arguments: const CombinationOfRows& binary_row
AddOneConstraint	Return type: void Arguments: glop::RowIndex, const std::vector<std::pair<glop::ColIndex, IntegerValue>>& terms, IntegerValue lb, IntegerValue ub
EliminateVarUsingRow	Return type: void Arguments: int col, int row Visible for testing. Adds the given row to all other rows having an odd cofficient on the given column. This then eliminate the entry (col, row) that is now a singleton by incresing the slack of the given row.
InterestingCandidates	Arguments: ModelRandomGenerator* random
MatrixCol	Return type: const std::vector<int>& Arguments: int col
MatrixRow	Return type: const CombinationOfRows& Arguments: int row
ProcessVariables	Return type: void Arguments: const std::vector<double>& lp_values, const std::vector<IntegerValue>& lower_bounds, const std::vector<IntegerValue>& upper_bounds Public API: ProcessVariables() must be called first and then constraints can be added one by one. Finally GetZeroHalfInterestingCuts() will return a set of good candidates. TODO(user): This is a first implementation, both the heuristic and the code performance can probably be improved uppon.
Reset	Return type: void Arguments: int size Visible for testing.
SymmetricDifference	Return type: void Arguments: std::function<bool(int)> extra_condition, const std::vector<int>& a, std::vector<int>* b Visible for testing. Like std::set_symmetric_difference, but use a vector instead of sort. This assumes tmp_marked_ to be all false. We don't DCHECK it here for speed, but it DCHECKed on each EliminateVarUsingRow() call. In addition, the result is filtered using the extra_condition function.