Add getConsVals (#1033)

* Add getConsVals

* fix memleak

* remove useless declarations

* Update src/pyscipopt/scip.pxi

Co-authored-by: DominikKamp <[email protected]>

* Update CHANGELOG.md

Co-authored-by: DominikKamp <[email protected]>

* generalize getRhs, getLhs

* Apply suggestions from code review

Co-authored-by: DominikKamp <[email protected]>

* Change name and better test

* Correct memory allocation in getConsVars

* return None at not success

* Apply suggestions from code review

Co-authored-by: DominikKamp <[email protected]>

* Update src/pyscipopt/scip.pxi

Co-authored-by: DominikKamp <[email protected]>

* Update src/pyscipopt/scip.pxi

Co-authored-by: DominikKamp <[email protected]>

---------

Co-authored-by: DominikKamp <[email protected]>

Author: Joao-Dionisio

CHANGELOG.md

@@ -9,6 +9,8 @@
 - Added addMatrixConsIndicator(), and tests
 - Added SCIPvarMarkRelaxationOnly, SCIPvarIsRelaxationOnly, SCIPvarMarkDeletable, SCIPvarIsDeletable, and tests
 - Wrapped SCIPgetNLPBranchCands
+- Added getConsVals() to get coefficients of any linear type constraint
+- Generalized getLhs() and getRhs() to additionally support any linear type constraint
 ### Fixed
 - Raised an error when an expression is used when a variable is required
 ### Changed

src/pyscipopt/scip.pxd

@@ -858,6 +858,7 @@ cdef extern from "scip/scip.h":
     SCIP_RETCODE SCIPtransformCons(SCIP* scip, SCIP_CONS* cons, SCIP_CONS** transcons)
     SCIP_RETCODE SCIPgetTransformedCons(SCIP* scip, SCIP_CONS* cons, SCIP_CONS** transcons)
     SCIP_RETCODE SCIPgetConsVars(SCIP* scip, SCIP_CONS* cons, SCIP_VAR** vars, int varssize, SCIP_Bool* success)
+    SCIP_RETCODE SCIPgetConsVals(SCIP* scip, SCIP_CONS* cons, SCIP_Real* vals, int valssize, SCIP_Bool* success)
     SCIP_RETCODE SCIPgetConsNVars(SCIP* scip, SCIP_CONS* cons, int* nvars, SCIP_Bool* success)
     SCIP_CONS** SCIPgetConss(SCIP* scip)
     const char* SCIPconsGetName(SCIP_CONS* cons)
@@ -1477,6 +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 SCIPconsGetLhs(SCIP* scip, SCIP_CONS* cons, SCIP_Bool* success)
+    SCIP_Real SCIPconsGetRhs(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 isLinearType(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', 'logicor', 'varbound')
+
     def isNonlinear(self):
         """
         Returns True if constraint is nonlinear.
@@ -6019,7 +6031,11 @@ cdef class Model:
 
         SCIPgetConsNVars(self._scip, constraint.scip_cons, &nvars, &success)
         _vars = <SCIP_VAR**> malloc(nvars * sizeof(SCIP_VAR*))
-        SCIPgetConsVars(self._scip, constraint.scip_cons, _vars, nvars*sizeof(SCIP_VAR*), &success)
+        SCIPgetConsVars(self._scip, constraint.scip_cons, _vars, nvars, &success)
+
+        if not success:
+            free(_vars)
+            return None
 
         vars = []
         for i in range(nvars):
@@ -6034,7 +6050,39 @@ cdef class Model:
                 self._modelvars[ptr] = var
                 vars.append(var)
 
+        free(_vars)
         return vars
+    
+    def getConsVals(self, Constraint constraint):
+        """
+        Returns the value array of an arbitrary SCIP constraint that can be represented as a single linear constraint.
+
+        Parameters
+        ----------
+        constraint : Constraint
+            Constraint to get the values from.
+
+        Returns
+        -------
+        list of float
+
+        """
+        cdef SCIP_Real* _vals
+        cdef int nvars
+        cdef SCIP_Bool success
+        cdef int i
+
+        nvars = self.getConsNVars(constraint)
+        _vals = <SCIP_Real*> malloc(nvars * sizeof(SCIP_Real))
+        PY_SCIP_CALL(SCIPgetConsVals(self._scip, constraint.scip_cons, _vals, nvars, &success))
+
+        if not success:
+            free(_vals)
+            return None
+
+        vals = [_vals[i] for i in range(nvars)]
+        free(_vals)
+        return vals
 
     def getNVarsAnd(self, Constraint and_cons):
         """
@@ -6050,8 +6098,6 @@ cdef class Model:
         int
 
         """
-        cdef int nvars
-        cdef SCIP_Bool success
 
         return SCIPgetNVarsAnd(self._scip, and_cons.scip_cons)
 
@@ -6069,9 +6115,9 @@ cdef class Model:
         list of Variable
 
         """
+        
         cdef SCIP_VAR** _vars
         cdef int nvars
-        cdef SCIP_Bool success
         cdef int i
 
         constype = bytes(SCIPconshdlrGetName(SCIPconsGetHdlr(and_cons.scip_cons))).decode('UTF-8')
@@ -6109,8 +6155,8 @@ cdef class Model:
         Variable
 
         """
+        
         cdef SCIP_VAR* _resultant
-        cdef SCIP_Bool success
 
         _resultant = SCIPgetResultantAnd(self._scip, and_cons.scip_cons)
 
@@ -6140,8 +6186,7 @@ cdef class Model:
         bool
 
         """
-        cdef SCIP_Bool success
-
+        
         return SCIPisAndConsSorted(self._scip, and_cons.scip_cons)
 
     def sortAndCons(self, Constraint and_cons):
@@ -6154,7 +6199,6 @@ cdef class Model:
             Constraint to sort.
 
         """
-        cdef SCIP_Bool success
 
         PY_SCIP_CALL(SCIPsortAndCons(self._scip, and_cons.scip_cons))
 
@@ -7270,9 +7314,13 @@ 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.isLinearType():
+            rhs = SCIPconsGetRhs(self._scip, cons.scip_cons, &success)
+            assert(success)
+            return rhs
         elif constype == 'nonlinear':
             return SCIPgetRhsNonlinear(cons.scip_cons)
         else:
@@ -7311,9 +7359,13 @@ 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.isLinearType():
+            lhs = SCIPconsGetLhs(self._scip, cons.scip_cons, &success)
+            assert(success)
+            return lhs
         elif constype == 'nonlinear':
             return SCIPgetLhsNonlinear(cons.scip_cons)
         else:

tests/test_cons.py

@@ -27,6 +27,23 @@ def test_getConsVars():
     c = m.addCons(quicksum(x[i] for i in x) <= 1)
     assert m.getConsVars(c) == [x[i] for i in x]
 
+def test_getConsVals():
+    n_vars = 100
+    m = Model()
+    x = {}
+    for i in range(n_vars):
+        x[i] = m.addVar("%i" % i, vtype="B")
+
+    c1 = m.addCons(quicksum(x[i] for i in x) <= 1)
+    c2 = m.addConsKnapsack([x[i] for i in x], [i for i in range(1, n_vars+1)], 10)
+    vals1 = m.getConsVals(c1)
+    vals2 = m.getConsVals(c2)
+
+    assert len(vals1) == n_vars
+    assert all(isinstance(v, float) for v in vals1)
+    assert len(vals2) == n_vars
+    assert all(isinstance(v, float) for v in vals2)
+    assert m.getConsVals(c2) == [i for i in range(1, n_vars+1)]
 
 def test_constraint_option_setting():
     m = Model()
@@ -266,6 +283,8 @@ def test_cons_knapsack():
     m.chgCapacityKnapsack(knapsack_cons, 5)
 
     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)