user_generate_cuts_in

user_generate_cuts_in_lp

int user_generate_cuts_in_lp(void *user, LPdata *lp_data, int varnum,
                             var_desc **vars, double *x, int *new_row_num,
                             cut_data ***cuts)

Description:

The user might decide to generate cuts directly within the LP module instead of using the cut generator. This can be accomplished either through a call to this function or simply by configuring SYMPHONY such that the cut generator is called directly from the LP solver. One example of when this might be done is when generating Gomory cuts or something else that requires knowledge of the current LP tableau. The user must return the list of generated cuts by allocating an array of cut_data structures and setting *cuts to point to this array. Post-processing consists of checking if any of the new cuts are already in the local pool (or dominated by a cut in the local pool).

Arguments:

void *user	IN	Pointer to the user-defined LP data structure.

LPdata *lp_data	IN	A pointer to SYMPHONY's internal data structure for storing the LP relaxation and related data.
int varnum	IN	The number of variables currently in the LP relaxation. (The length of the *vars and x arrays.)
var_desc **vars	IN	The variables currently in the LP relaxation.
double *x	IN	Values of the above variables.
int *new_row_num	OUT	The number of cuts generated.
cut_data ***cuts	OUT	The cuts and the corresponding rows.

Return values:

USER_ERROR	Error. Interpreted as if no cuts were generated.
USER_SUCCESS	Cuts were generated.
USER_DEFAULT	No cuts were generated. By default, SYMPHONY uses the CGL to generate generic cuts, according to parameter settings.
GENERATE_CGL_CUTS	Generate generic CGL cuts, according to parameter settings.
DO_NOT_GENERATE_CGL_CUTS	No additional cuts are generated.

Post-processing:

SYMPHONY checks if any of the newly generated cuts are already in the local pool.

Wrapper invoked from:

receive_cuts() before the cuts from the CG module are received. Since the user will probably use this function to generate tableau-dependent cuts, it is highly unlikely that any of the new cuts would already be in the pool. Therefore the user will probably return USER_AND_PP to force SYMPHONY to skip post-processing.

Notes:

Just like in user_unpack_cuts(), the user has to allocate space for the rows.
Unless the name field of a cut is explicitly set to CUT__SEND_TO_CP, SYMPHONY will assume that the cut is locally valid only and set that field to CUT__DO_NOT_SEND_TO_CP.