is_presolve

Returns if presolve level specified in testmask is active.

unsigned char is_presolve(lprec *lp, int testmask);

Return Value

is_presolve returns TRUE or FALSE.

Parameters

Pointer to previously created lp model. See return value of make_lp, read_lp, read_LP, read_lpt, read_LPT, read_mps, read_freemps, read_MPS, read_freeMPS, read_XLI

testmask

PRESOLVE_NONE (0)	No presolve at all
PRESOLVE_ROWS (1)	Presolve rows
PRESOLVE_COLS (2)	Presolve columns
PRESOLVE_LINDEP (4)	Eliminate linearly dependent rows
PRESOLVE_SOS (32)	Convert constraints to SOSes (only SOS1 handled)
PRESOLVE_REDUCEMIP (64)	If the phase 1 solution process finds that a constraint is redundant then this constraint is deleted
PRESOLVE_DUALS (128)	Calculate duals
PRESOLVE_SENSDUALS (256)	Calculate sensitivity if there are integer variables

Remarks

The is_presolve function returns a flag if the presolve level specified in testmask is active. Presolve looks at the model and tries to simplify it so that solving times are shorter. For example a constraint on only one variable is converted to a bound on this variable (and the constraint is deleted). Note that the model dimensions can change because of this, so be careful with this. Both rows and columns can be deleted by the presolve.
The default is not (FALSE) doing a presolve.

Example

#include <stdio.h>
#include <stdlib.h>
#include "lp_lib.h"

int main(void)
{
  lprec *lp;
  int presolve;

  /* Create a new LP model */
  lp = make_lp(0, 0);
  if(lp == NULL) {
    fprintf(stderr, "Unable to create new LP model\n");
    return(1);
  }

  presolve = is_presolve(lp, PRESOLVE_ROWS | PRESOLVE_COLS); /* Will return FALSE */

  delete_lp(lp);
  return(0);
}

lp_solve API reference