Fix binary operations between GenExpr and MatrixExpr

src/pyscipopt/expr.pxi

@@ -146,7 +146,7 @@ def buildGenExprObj(expr):
         GenExprs = np.empty(expr.shape, dtype=object)
         for idx in np.ndindex(expr.shape):
             GenExprs[idx] = buildGenExprObj(expr[idx])
-        return GenExprs
+        return GenExprs.view(MatrixExpr)
 
     else:
         assert isinstance(expr, GenExpr)
@@ -223,6 +223,9 @@ cdef class Expr:
         return self
 
     def __mul__(self, other):
+        if isinstance(other, MatrixExpr):
+            return other * self
+
         if _is_number(other):
             f = float(other)
             return Expr({v:f*c for v,c in self.terms.items()})
@@ -420,6 +423,9 @@ cdef class GenExpr:
         return UnaryExpr(Operator.fabs, self)
 
     def __add__(self, other):
+        if isinstance(other, MatrixExpr):
+            return other + self
+
         left = buildGenExprObj(self)
         right = buildGenExprObj(other)
         ans = SumExpr()
@@ -475,6 +481,9 @@ cdef class GenExpr:
     #    return self
 
     def __mul__(self, other):
+        if isinstance(other, MatrixExpr):
+            return other * self
+
         left = buildGenExprObj(self)
         right = buildGenExprObj(other)
         ans = ProdExpr()
@@ -537,7 +546,7 @@ cdef class GenExpr:
     def __truediv__(self,other):
         divisor = buildGenExprObj(other)
         # we can't divide by 0
-        if divisor.getOp() == Operator.const and divisor.number == 0.0:
+        if isinstance(divisor, GenExpr) and divisor.getOp() == Operator.const and divisor.number == 0.0:
             raise ZeroDivisionError("cannot divide by 0")
         return self * divisor**(-1)
 

tests/test_matrix_variable.py

@@ -1,8 +1,10 @@
+import operator
 import pdb
 import pprint
 import pytest
 from pyscipopt import Model, Variable, log, exp, cos, sin, sqrt
 from pyscipopt import Expr, MatrixExpr, MatrixVariable, MatrixExprCons, MatrixConstraint, ExprCons
+from pyscipopt.scip import GenExpr
 from time import time
 
 import numpy as np
@@ -392,3 +394,22 @@ def test_matrix_cons_indicator():
     assert m.getVal(is_equal).sum() == 2
     assert (m.getVal(x) == m.getVal(y)).all().all()
     assert (m.getVal(x) == np.array([[5, 5, 5], [5, 5, 5]])).all().all()
+
+
+_binop_model = Model()
+
+def var():
+    return _binop_model.addVar()
+
+def genexpr():
+    return _binop_model.addVar() ** 0.6
+
+def matvar():
+    return _binop_model.addMatrixVar((1,))
+
+@pytest.mark.parametrize("right", [var(), genexpr(), matvar()], ids=["var", "genexpr", "matvar"])
+@pytest.mark.parametrize("left", [var(), genexpr(), matvar()], ids=["var", "genexpr", "matvar"])
+@pytest.mark.parametrize("op", [operator.add, operator.sub, operator.mul, operator.truediv])
+def test_binop(op, left, right):
+    res = op(left, right)
+    assert isinstance(res, (Expr, GenExpr, MatrixExpr))