user_logical_fixing

[cf]user_logical_fixing

int user_logical_fixing(void *user, int varnum, var_desc **vars, 
                        double *x, char *status, int *num_fixed)

Description:

Logical fixing is modifying the stati of variables based on logical implications derived from problem-specific information. In this function the user can modify the status of any variable. Valid stati are: NOT_FIXED, TEMP_FIXED_TO_LB, PERM_FIXED_TO_LB, TEMP_FIXED_TO_UB and PERM_FIXED_TO_UB. Be forewarned that fallaciously fixing a variable in this function can cause the algorithm to terminate improperly. Generally, a variable can only be fixed permanently if the matrix is full at the time of the fixing (i.e. all variables that are not fixed are in the matrix). There are no default options.

Arguments:

void *user	IN	Pointer to the user-defined LP data structure.
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.
char *status	INOUT	Stati of variables currently in the LP relaxation.
int *num_fixed	OUT	Number of fixed variables.

Return values:

USER_ERROR	Error. Ignored by SYMPHONY.
USER_SUCCESS	User changed the stati of the variables she wanted.
USER_DEFAULT	No logical fixing rules are implemented.

Wrapper invoked from:

fix_variables() after doing reduced cost fixing, but only when a specified number of variables have been fixed by reduced cost (see LP parameter settings).