generalize getRhs, getLhs

Author: Joao-Dionisio

CHANGELOG.md

@@ -10,6 +10,7 @@
 - Added SCIPvarMarkRelaxationOnly, SCIPvarIsRelaxationOnly, SCIPvarMarkDeletable, SCIPvarIsDeletable, and tests
 - Wrapped SCIPgetNLPBranchCands
 - Added getConsVals() and generalized getLhs() as well as getRhs() for linear type constraints
+- Generalized getRhs() to use SCIPconsGetRhs(), same for getLhs().
 ### Fixed
 - Raised an error when an expression is used when a variable is required
 ### Changed

src/pyscipopt/scip.pxd

@@ -1478,6 +1478,8 @@ cdef extern from "scip/cons_linear.h":
     SCIP_RETCODE SCIPchgRhsLinear(SCIP* scip, SCIP_CONS* cons, SCIP_Real rhs)
     SCIP_Real SCIPgetLhsLinear(SCIP* scip, SCIP_CONS* cons)
     SCIP_Real SCIPgetRhsLinear(SCIP* scip, SCIP_CONS* cons)
+    SCIP_Real SCIPconsGetRhs(SCIP* scip, SCIP_CONS* cons, SCIP_Bool* success)
+    SCIP_Real SCIPconsGetLhs(SCIP* scip, SCIP_CONS* cons, SCIP_Bool* success)
     SCIP_RETCODE SCIPchgCoefLinear(SCIP* scip, SCIP_CONS* cons, SCIP_VAR* var, SCIP_Real newval)
     SCIP_RETCODE SCIPdelCoefLinear(SCIP* scip, SCIP_CONS* cons, SCIP_VAR*)
     SCIP_RETCODE SCIPaddCoefLinear(SCIP* scip, SCIP_CONS* cons, SCIP_VAR*, SCIP_Real val)

src/pyscipopt/scip.pxi

@@ -2196,6 +2196,18 @@ cdef class Constraint:
         constype = bytes(SCIPconshdlrGetName(SCIPconsGetHdlr(self.scip_cons))).decode('UTF-8')
         return constype == 'knapsack'
 
+    def isLinearRepresentable(self):
+        """
+        Returns True if constraint can be represented as a linear constraint.
+
+        Returns
+        -------
+        bool
+
+        """
+        constype = bytes(SCIPconshdlrGetName(SCIPconsGetHdlr(self.scip_cons))).decode('UTF-8')
+        return constype in ('linear', 'knapsack', 'setppc')
+
     def isNonlinear(self):
         """
         Returns True if constraint is nonlinear.
@@ -7293,13 +7305,13 @@ cdef class Model:
         float
 
         """
+        cdef SCIP_Bool success
         constype = bytes(SCIPconshdlrGetName(SCIPconsGetHdlr(cons.scip_cons))).decode('UTF-8')
-        if constype == 'linear':
-            return SCIPgetRhsLinear(self._scip, cons.scip_cons)
+
+        if cons.isLinearRepresentable():
+            return SCIPconsGetRhs(self._scip, cons.scip_cons, &success)
         elif constype == 'nonlinear':
             return SCIPgetRhsNonlinear(cons.scip_cons)
-        elif constype == 'knapsack':
-            return SCIPgetCapacityKnapsack(self._scip, cons.scip_cons)
         else:
             raise Warning("method cannot be called for constraints of type " + constype)
 
@@ -7336,9 +7348,11 @@ cdef class Model:
         float
 
         """
+        cdef SCIP_Bool success
         constype = bytes(SCIPconshdlrGetName(SCIPconsGetHdlr(cons.scip_cons))).decode('UTF-8')
-        if constype == 'linear':
-            return SCIPgetLhsLinear(self._scip, cons.scip_cons)
+
+        if cons.isLinearRepresentable():
+            return SCIPconsGetLhs(self._scip, cons.scip_cons, &success)
         elif constype == 'nonlinear':
             return SCIPgetLhsNonlinear(cons.scip_cons)
         else:

tests/test_cons.py

@@ -283,6 +283,7 @@ def test_cons_knapsack():
 
     assert m.getCapacityKnapsack(knapsack_cons) == 5
     assert m.getRhs(knapsack_cons) == 5
+    assert m.getLhs(knapsack_cons) == -m.infinity()
 
     m.addCoefKnapsack(knapsack_cons, z, 3)
     weights = m.getWeightsKnapsack(knapsack_cons)