Function testIis

check/TestCAPI.c:2191–2408

}

void testIis() {
  void* highs = Highs_create();
  Highs_setBoolOptionValue(highs, "output_flag", dev_run);
  HighsInt ret;
  double inf = Highs_getInfinity(highs);
  // For the constraints
  //
  // x + y - z = 2
  //
  // x + y + z <= 5
  //
  // x + 2y + z <= 1
  //
  // with variables in [0, 1], constraints 0 and 2 form an IIS with
  // 
  // x free; 0 <= y; 0 <= z
  //
  // x + y - z >= 2; x + 2y + z <= 1
  //
  // x may be free, but can't immediately be removed, otherwise
  // removing y >= 0 yields an infeasible LP
  //
  ret = Highs_addCol(highs, 0.0, 0.0, 1.0, 0, NULL, NULL);
  assert(ret == 0);
  ret = Highs_addCol(highs, 0.0, 0.0, 1.0, 0, NULL, NULL);
  assert(ret == 0);
  ret = Highs_addCol(highs, 0.0, 0.0, 1.0, 0, NULL, NULL);
  assert(ret == 0);
  HighsInt index[3] = {0, 1, 2};
  double value_1[3] = {1, 1, -1};
  double value_2[3] = {1, 1, 1};
  double value_3[3] = {1, 2, 1};
  ret = Highs_addRow(highs,  2.0, 2.0, 3, index, value_1);
  assert(ret == 0);
  ret = Highs_addRow(highs, -inf, 5.0, 3, index, value_2);
  assert(ret == 0);
  ret = Highs_addRow(highs, -inf, 1.0, 3, index, value_3);
  assert(ret == 0);

  HighsInt num_col;
  HighsInt num_row;
  HighsInt num_nz;
  HighsInt sense;
  double offset;
  ret = Highs_getLp(highs, kHighsMatrixFormatRowwise,
		    &num_col, &num_row, &num_nz,
		    &sense, &offset,
		    NULL, NULL, NULL, 
		    NULL, NULL,
		    NULL, NULL, NULL,
		    NULL);

  for (int k = 0 ; k < 2; k++) {
    HighsInt iis_num_col;
    HighsInt iis_num_row;
    ret = Highs_getIis(highs,
		       &iis_num_col, &iis_num_row,
		       NULL, NULL,