Add three functions for variables (#1107)

* add function to get variable status

* add isActive to get whether variable is active

* add markDoNotMultaggrVar to mark a variable

* Update src/pyscipopt/scip.pxi

Co-authored-by: João Dionísio <[email protected]>

* Update src/pyscipopt/scip.pxi

Co-authored-by: João Dionísio <[email protected]>

* Add markDoNotAggrVar and minor readme changes

* formatting in scip.pxi

* add test for variable marking

* test getStatus as well

---------

Co-authored-by: João Dionísio <[email protected]>
Co-authored-by: Joao-Dionisio <[email protected]>

Author: pfetsch

CHANGELOG.md

@@ -7,6 +7,10 @@
 - MatrixVariable comparisons (<=, >=, ==) now support numpy's broadcast feature.
 - Added methods: getMaxDepth(), getPlungeDepth(), getLowerbound(), getCutoffbound(), getNNodeLPIterations(), getNStrongbranchLPIterations().
 - setup.py now automatically detects conda environments when SCIPOPTDIR is not defined.
+- Added function getStatus() to get variable status in variable class
+- Added function isActive() to get whether a variable is active in variable class
+- Added function markDoNotAggrVar() to prevent a variable from being aggregated
+- Added function markDoNotMultaggrVar() to prevent a variable from being multi-aggregated
 ### Fixed
 - Implemented all binary operations between MatrixExpr and GenExpr
 - Fixed the type of @ matrix operation result from MatrixVariable to MatrixExpr.

src/pyscipopt/scip.pxd

@@ -30,6 +30,16 @@ cdef extern from "scip/scip.h":
         SCIP_VARTYPE SCIP_VARTYPE_IMPLINT
         SCIP_VARTYPE SCIP_VARTYPE_CONTINUOUS
 
+    ctypedef int SCIP_VARSTATUS
+    cdef extern from "scip/type_var.h":
+        SCIP_VARSTATUS SCIP_VARSTATUS_ORIGINAL
+        SCIP_VARSTATUS SCIP_VARSTATUS_LOOSE
+        SCIP_VARSTATUS SCIP_VARSTATUS_COLUMN
+        SCIP_VARSTATUS SCIP_VARSTATUS_FIXED
+        SCIP_VARSTATUS SCIP_VARSTATUS_AGGREGATED
+        SCIP_VARSTATUS SCIP_VARSTATUS_MULTAGGR
+        SCIP_VARSTATUS SCIP_VARSTATUS_NEGATED
+
     ctypedef int SCIP_OBJSENSE
     cdef extern from "scip/type_prob.h":
         SCIP_OBJSENSE SCIP_OBJSENSE_MAXIMIZE
@@ -768,6 +778,8 @@ cdef extern from "scip/scip.h":
     SCIP_RETCODE SCIPdelVar(SCIP* scip, SCIP_VAR* var, SCIP_Bool* deleted)
 
     SCIP_RETCODE SCIPchgVarType(SCIP* scip, SCIP_VAR* var, SCIP_VARTYPE vartype, SCIP_Bool* infeasible)
+    SCIP_RETCODE SCIPmarkDoNotAggrVar(SCIP* scip, SCIP_VAR* var)
+    SCIP_RETCODE SCIPmarkDoNotMultaggrVar(SCIP* scip, SCIP_VAR* var)
     SCIP_RETCODE SCIPcaptureVar(SCIP* scip, SCIP_VAR* var)
     SCIP_RETCODE SCIPaddPricedVar(SCIP* scip, SCIP_VAR* var, SCIP_Real score)
     SCIP_RETCODE SCIPreleaseVar(SCIP* scip, SCIP_VAR** var)
@@ -790,8 +802,10 @@ cdef extern from "scip/scip.h":
     int SCIPgetNImplVars(SCIP* scip)
     int SCIPgetNContVars(SCIP* scip)
     SCIP_VARTYPE SCIPvarGetType(SCIP_VAR* var)
+    SCIP_VARSTATUS SCIPvarGetStatus(SCIP_VAR* var)
     SCIP_Bool SCIPvarIsOriginal(SCIP_VAR* var)
     SCIP_Bool SCIPvarIsTransformed(SCIP_VAR* var)
+    SCIP_Bool SCIPvarIsActive(SCIP_VAR* var)
     SCIP_COL* SCIPvarGetCol(SCIP_VAR* var)
     SCIP_Bool SCIPvarIsInLP(SCIP_VAR* var)
     SCIP_Real SCIPvarGetLbOriginal(SCIP_VAR* var)

src/pyscipopt/scip.pxi

@@ -1120,7 +1120,6 @@ cdef class Solution:
         PY_SCIP_CALL(SCIPtranslateSubSol(target._scip, self.scip, self.sol, NULL, source_vars, &(targetSol.sol)))
         return targetSol
 
-
 cdef class BoundChange:
     """Bound change."""
 
@@ -1538,6 +1537,32 @@ cdef class Variable(Expr):
         elif vartype == SCIP_VARTYPE_IMPLINT:
             return "IMPLINT"
 
+    def getStatus(self):
+        """
+        Retrieve the variable status (ORIGINAL, LOOSE, COLUMN, FIXED, AGGREGATED, MULTAGGR, NEGATED)
+
+        Returns
+        -------
+        str
+            "ORIGINAL", "LOOSE", "COLUMN", "FIXED", "AGGREGATED", "MULTAGGR", "NEGATED"
+
+        """
+        varstatus = SCIPvarGetStatus(self.scip_var)
+        if varstatus == SCIP_VARSTATUS_ORIGINAL:
+            return "ORIGINAL"
+        elif varstatus == SCIP_VARSTATUS_LOOSE:
+            return "LOOSE"
+        elif varstatus == SCIP_VARSTATUS_COLUMN:
+            return "COLUMN"
+        elif varstatus == SCIP_VARSTATUS_FIXED:
+            return "FIXED"
+        elif varstatus == SCIP_VARSTATUS_AGGREGATED:
+            return "AGGREGATED"
+        elif varstatus == SCIP_VARSTATUS_MULTAGGR:
+            return "MULTAGGR"
+        elif varstatus == SCIP_VARSTATUS_NEGATED:
+            return "NEGATED"
+
     def isOriginal(self):
         """
         Retrieve whether the variable belongs to the original problem
@@ -1549,6 +1574,17 @@ cdef class Variable(Expr):
         """
         return SCIPvarIsOriginal(self.scip_var)
 
+    def isActive(self):
+        """
+        Retrieve whether the variable is active
+
+        Returns
+        -------
+        bool
+
+        """
+        return SCIPvarIsActive(self.scip_var)
+
     def isInLP(self):
         """
         Retrieve whether the variable is a COLUMN variable that is member of the current LP.
@@ -1560,7 +1596,6 @@ cdef class Variable(Expr):
         """
         return SCIPvarIsInLP(self.scip_var)
 
-
     def getIndex(self):
         """
         Retrieve the unique index of the variable.
@@ -2043,7 +2078,6 @@ class MatrixVariable(MatrixExpr):
             mayround[idx] = self[idx].varMayRound()
         return mayround
 
-
 cdef class Constraint:
     """Base class holding a pointer to corresponding SCIP_CONS"""
 
@@ -2584,7 +2618,6 @@ cdef class Model:
             else:
                 PY_SCIP_CALL(SCIPcopy(sourceModel._scip, self._scip, NULL, NULL, n, globalcopy, enablepricing, threadsafe, True, self._valid))
 
-
     def attachEventHandlerCallback(self,
         callback,
         events,
@@ -2634,7 +2667,6 @@ cdef class Model:
 
         self.includeEventhdlr(event_handler, name, description)
 
-
     def __dealloc__(self):
         # call C function directly, because we can no longer call this object's methods, according to
         # http://docs.cython.org/src/reference/extension_types.html#finalization-dealloc
@@ -2817,7 +2849,6 @@ cdef class Model:
         """
         return SCIPminorVersion()
 
-
     def getTechVersion(self):
         """
         Retrieve SCIP technical version.
@@ -3559,7 +3590,6 @@ cdef class Model:
         return iters
 
     # Objective function
-
     def setMinimize(self):
         """Set the objective sense to minimization."""
         PY_SCIP_CALL(SCIPsetObjsense(self._scip, SCIP_OBJSENSE_MINIMIZE))
@@ -3905,7 +3935,6 @@ cdef class Model:
         locale.setlocale(locale.LC_NUMERIC,user_locale)
 
     # Variable Functions
-
     def addVar(self, name='', vtype='C', lb=0.0, ub=None, obj=0.0, pricedVar=False, pricedVarScore=1.0, deletable=False):
         """
         Create a new variable. Default variable is non-negative and continuous.
@@ -4385,7 +4414,6 @@ cdef class Model:
            ub = SCIPinfinity(self._scip)
         PY_SCIP_CALL(SCIPchgVarUbNode(self._scip, node.scip_node, var.scip_var, ub))
 
-
     def chgVarType(self, Variable var, vtype):
         """
         Changes the type of a variable.
@@ -4413,6 +4441,28 @@ cdef class Model:
         if infeasible:
             print('could not change variable type of variable %s' % var)
 
+    def markDoNotAggrVar(self, Variable var):
+        """
+        Marks a variable preventing it from being aggregated.
+
+        Parameters
+        ----------
+        var : Variable
+            variable to mark
+        """
+        PY_SCIP_CALL(SCIPmarkDoNotAggrVar(self._scip, var.scip_var))
+
+    def markDoNotMultaggrVar(self, Variable var):
+        """
+        Marks a variable preventing it from being multi-aggregated.
+
+        Parameters
+        ----------
+        var : Variable
+            variable to mark
+        """
+        PY_SCIP_CALL(SCIPmarkDoNotMultaggrVar(self._scip, var.scip_var))
+
     def getVars(self, transformed=False):
         """
         Retrieve all variables.
@@ -4754,7 +4804,6 @@ cdef class Model:
         """Marks the given node to be propagated again the next time a node of its subtree is processed."""
         PY_SCIP_CALL(SCIPrepropagateNode(self._scip, node.scip_node))
 
-
     # LP Methods
     def getLPSolstat(self):
         """
@@ -4767,7 +4816,6 @@ cdef class Model:
         """
         return SCIPgetLPSolstat(self._scip)
 
-
     def constructLP(self):
         """
         Makes sure that the LP of the current node is loaded and
@@ -7044,7 +7092,6 @@ cdef class Model:
 
         return pyCons
 
-
     def addMatrixConsIndicator(self, cons: Union[ExprCons, MatrixExprCons], binvar: Union[Variable, MatrixVariable] = None,
                                activeone: Union[bool, np.ndarray] = True, name: Union[str, np.ndarray] = "",
                                initial: Union[bool, np.ndarray] = True, separate: Union[bool, np.ndarray] = True,
@@ -7627,7 +7674,6 @@ cdef class Model:
 
         return activity
 
-
     def getSlack(self, Constraint cons, Solution sol = None, side = None):
         """
         Retrieve slack of given constraint.
@@ -8648,7 +8694,6 @@ cdef class Model:
         """
         PY_SCIP_CALL( SCIPincludeBendersDefaultCuts(self._scip, benders._benders) )
 
-
     def includeEventhdlr(self, Eventhdlr eventhdlr, name, desc):
         """
         Include an event handler.
@@ -9285,7 +9330,6 @@ cdef class Model:
         # TODO: It might be necessary in increment the reference to benders i.e Py_INCREF(benders)
         Py_INCREF(benderscut)
 
-
     def getLPBranchCands(self):
         """
         Gets branching candidates for LP solution branching (fractional variables) along with solution values,
@@ -9329,9 +9373,9 @@ cdef class Model:
         """
         Gets number of branching candidates for LP solution branching (number of fractional variables)
 
- 	Returns
-  	-------
-   	int
+        Returns
+        -------
+        int
     	    number of LP branching candidates
 
         """
@@ -9388,7 +9432,6 @@ cdef class Model:
         PY_SCIP_CALL(SCIPbranchVar(self._scip, wrapper.ptr[0], &downchild, &eqchild, &upchild))
         return Node.create(downchild), Node.create(eqchild), Node.create(upchild)
 
-
     def branchVarVal(self, Variable variable, value):
         """
         Branches on variable using a value which separates the domain of the variable.
@@ -10992,7 +11035,6 @@ cdef class Model:
             v = str_conversion(value)
             PY_SCIP_CALL(SCIPsetStringParam(self._scip, n, v))
 
-
     def getParam(self, name):
         """
         Get the value of a parameter of type
@@ -11482,7 +11524,6 @@ cdef class Model:
         """
         return SCIPgetTreesizeEstimation(self._scip)
 
-
     def getBipartiteGraphRepresentation(self, prev_col_features=None, prev_edge_features=None, prev_row_features=None,
                                         static_only=False, suppress_warnings=False):
         """

tests/test_vars.py

@@ -111,3 +111,36 @@ def test_getNBranchingsCurrentRun():
         n_branchings += var.getNBranchingsCurrentRun(SCIP_BRANCHDIR.DOWNWARDS)
 
     assert n_branchings == m.getNNodes() - 1
+
+def test_markDoNotAggrVar_and_getStatus():
+    model = Model()
+    x = model.addVar("x", obj=2, lb=0, ub=10)
+    y = model.addVar("y", obj=3, lb=0, ub=20)
+    z = model.addVar("z", obj=1, lb=0, ub=10)
+    w = model.addVar("w", obj=4, lb=0, ub=15)
+
+    model.addCons(y - 2*x == 0)
+    model.addCons(x + z + w == 10)
+    model.addCons(x*y*z >= 21) # to prevent presolve from removing all variables
+    model.presolve()
+
+    assert z.getStatus() == "ORIGINAL"
+    assert model.getTransformedVar(z).getStatus() == "AGGREGATED"
+    assert model.getTransformedVar(w).getStatus() == "MULTAGGR"
+
+    assert model.getNVars(True) == 1
+
+    model.freeTransform()
+    model.markDoNotMultaggrVar(w)
+    model.presolve()
+
+    assert model.getTransformedVar(w).getStatus() != "MULTAGGR"
+    assert model.getNVars(True) == 3
+
+    model.freeTransform()
+    model.markDoNotAggrVar(y)
+    model.presolve()
+    assert model.getTransformedVar(z).getStatus() != "AGGREGATED"
+    assert model.getNVars(True) == 4
+
+    assert x.getStatus() == "ORIGINAL"