adapt assert to Gurobi version

In older Gurobi versions (prior to version 12),
the barrier does not return valid objective bounds.
For newer versions, there might be an epsilon
difference.

Author: pfetsch

src/lpi/lpi_grb.c

@@ -4166,14 +4166,20 @@ SCIP_RETCODE SCIPlpiGetObjval(
 
 #ifndef NDEBUG
    {
+      /* in older version the barrier method does not seem to return valid objective bounds */
+#if GRB_VERSION_MAJOR < 12
       double obnd = -GRB_INFINITY;
       int algo;
-
-      (void)GRBgetintparam(lpi->grbenv, GRB_INT_PAR_METHOD, &algo);
       (void)GRBgetdblattr(lpi->grbmodel, GRB_DBL_ATTR_OBJBOUND, &obnd);
-
-      /* currently the barrier method does not seem to return valid objective bounds */
+      (void)GRBgetintparam(lpi->grbenv, GRB_INT_PAR_METHOD, &algo);
       assert(algo == GRB_METHOD_BARRIER || lpi->solstat != GRB_OPTIMAL || *objval == obnd); /*lint !e777*/
+#else
+      double obnd;
+      double eps;
+      (void)GRBgetdblattr(lpi->grbmodel, GRB_DBL_ATTR_OBJBOUND, &obnd);
+      (void)GRBgetdblparam(lpi->grbenv, GRB_DBL_PAR_FEASIBILITYTOL, &eps);
+      assert(lpi->solstat != GRB_OPTIMAL || fabs(*objval - obnd) <= eps); /*lint !e777*/
+#endif
    }
 #endif