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user_unpack_cuts

 

int user_unpack_cuts(void *user, int from, int one_row_only, int varnum, 
                     var_desc **vars, int cutnum, cut_data **cuts,
                     int *new_row_num, waiting_row ***new_rows)

Description:

The user has to interpret the given cuts as constraints for the current LP relaxation, i.e., he must decode the compact representation of the cuts (see the cut_data structure) into rows for the matrix. A pointer to the array of generated rows must be returned in ***new_rows (the user has to allocate this array) and their number in *new_row_num.

There is no post processing. There are no built-in default options.

Arguments:

Return values:

Wrapper invoked from:

Wherever a cut needs to be unpacked (multiple places).

Notes:

• When decoding the cuts, the expanded constraints have to be adjusted to the current LP, i.e., coefficients corresponding to variables currently not in the LP have to be left out.
• If the one_row_only flag is set to UNPACK_CUTS_MULTIPLE, then the user can generate as many constraints (even zero!) from a cut as she wants (this way she can lift the cuts, thus adjusting them for the current LP). However, if the flag is set to UNPACK_CUTS_SINGLE, then for each cut the user must generate a unique row, the same one that had been generated from the cut before. (The flag is set to this value only when regenerating a search tree node.)
• The from argument can take on six different values: CUT_FROM_CG, CUT_FROM_CP, CUT_FROM_TM, CUT_LEFTOVER (these are cuts from a previous LP relaxation that are still in the local pool), CUT_NOT_IN_MATRIX_SLACK and CUT_VIOLATED_SLACK indicating where the cut came from. This might be useful in deciding whether to lift the cut or not.
• The matind fields of the rows must be filled with indices with respect to the position of the variables in **vars.
• Warning: For each row, the user must make sure that the cut the row was generated from (and can be uniquely regenerated from if needed later) is safely stored in the waiting_row structure. SYMPHONY will free the entries in cuts after this function returns. If a row is generated from a cut in cuts (and not from a lifted cut), the user has the option of physically copying the cut into the corresponding part of the waiting_row structure, or copying the pointer to the cut into the waiting_row structure and erasing the pointer in cuts. If a row is generated from a lifted cut, the user should store a copy of the lifted cut in the corresponding part of waiting_row.