Add SCIPvarMarkRelaxationOnly (#1023)

* Add SCIPvarMarkRelaxationOnly

* Fix and add isRelaxationOnly

* remove debug flag

* varDeletable functions

Author: Joao-Dionisio

CHANGELOG.md

@@ -7,6 +7,7 @@
 - Added isPositive(), isNegative(), isFeasLE(), isFeasLT(), isFeasGE(), isFeasGT(), isHugeValue(), and tests
 - Added SCIP_LOCKTYPE, addVarLocksType(), getNLocksDown(), getNLocksUp(), getNLocksDownType(), getNLocksUpType(), and tests
 - Added addMatrixConsIndicator(), and tests
+- Added SCIPvarMarkRelaxationOnly, SCIPvarIsRelaxationOnly, SCIPvarMarkDeletable, SCIPvarIsDeletable, and tests
 ### Fixed
 - Raised an error when an expression is used when a variable is required
 ### Changed

src/pyscipopt/scip.pxd

@@ -817,6 +817,10 @@ cdef extern from "scip/scip.h":
     void SCIPvarSetData(SCIP_VAR* var, SCIP_VARDATA* vardata)
     SCIP_VARDATA* SCIPvarGetData(SCIP_VAR* var)
     SCIP_Real SCIPvarGetAvgSol(SCIP_VAR* var)
+    void SCIPvarMarkRelaxationOnly(SCIP_VAR* var)
+    SCIP_Bool SCIPvarIsRelaxationOnly(SCIP_VAR* var)
+    void SCIPvarMarkDeletable(SCIP_VAR* var)
+    SCIP_Bool SCIPvarIsDeletable(SCIP_VAR* var)
     SCIP_Real SCIPgetVarPseudocost(SCIP* scip, SCIP_VAR* var, SCIP_BRANCHDIR dir)
     SCIP_Real SCIPvarGetCutoffSum(SCIP_VAR* var, SCIP_BRANCHDIR dir)
     SCIP_Longint SCIPvarGetNBranchings(SCIP_VAR* var, SCIP_BRANCHDIR dir)

src/pyscipopt/scip.pxi

@@ -1677,6 +1677,49 @@ cdef class Variable(Expr):
         """
         return SCIPvarGetAvgSol(self.scip_var)
 
+    def markRelaxationOnly(self):
+        """
+        marks that this variable has only been introduced to define a relaxation
+
+        The variable must not have a coefficient in the objective and must be deletable.
+        If it is not marked deletable, it will be marked as deletable, which is only possible before
+        the variable is added to a problem.
+
+        Returns
+        -------
+        None
+
+        """
+        SCIPvarMarkRelaxationOnly(self.scip_var)
+    
+    def isRelaxationOnly(self):
+        """
+        returns whether a variable has been introduced to define a relaxation
+
+        These variables are only valid for the current SCIP solve round, they are not contained in any (checked)
+        constraints, but may be used in cutting planes, for example. Relaxation-only variables are not copied 
+        by SCIPcopyVars and cuts that contain these variables are not added as linear constraints when 
+        restarting or transferring information from a copied SCIP to a SCIP. Also conflicts with relaxation-only
+        variables are not generated at the moment. Relaxation-only variables do not appear in the objective.
+
+        Returns
+        -------
+        bool
+
+        """
+        return SCIPvarIsRelaxationOnly(self.scip_var)
+    
+    def isDeletable(self):
+        """
+        Returns whether variable is allowed to be deleted completely from the problem.
+
+        Returns
+        -------
+        bool
+
+        """
+        return SCIPvarIsDeletable(self.scip_var)
+
     def getNLocksDown(self):
         """
         Returns the number of locks for rounding down.
@@ -3745,7 +3788,7 @@ cdef class Model:
 
     # Variable Functions
 
-    def addVar(self, name='', vtype='C', lb=0.0, ub=None, obj=0.0, pricedVar=False, pricedVarScore=1.0):
+    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.
 
@@ -3801,6 +3844,9 @@ cdef class Model:
         else:
             raise Warning("unrecognized variable type")
 
+        if deletable:
+            SCIPvarMarkDeletable(scip_var)
+
         if pricedVar:
             PY_SCIP_CALL(SCIPaddPricedVar(self._scip, scip_var, pricedVarScore))
         else:

tests/test_vars.py

@@ -64,4 +64,19 @@ def test_vtype():
     assert x.vtype() == "INTEGER"
 
     m.chgVarType(y, 'M')
-    assert y.vtype() == "IMPLINT"
+    assert y.vtype() == "IMPLINT"
+
+def test_markRelaxationOnly():
+    m = Model()
+
+    x = m.addVar(vtype='C', lb=-5.5, ub=8, deletable=True)
+    y = m.addVar(vtype='I', lb=-5.2, ub=8)
+
+    assert not x.isRelaxationOnly()
+    assert not y.isRelaxationOnly()
+
+    x.markRelaxationOnly()
+    assert x.isRelaxationOnly()
+    assert x.isDeletable()
+    assert not y.isRelaxationOnly()
+    assert not y.isDeletable()