Merge SumExpr into Expr

Merged SumExpr functionality into Expr, simplifying sum expression logic and normalization. Updated PolynomialExpr to inherit directly from Expr. Adjusted Model class to handle Expr instead of SumExpr for sum expressions. This refactor streamlines expression management and reduces class complexity.
scipopt · Zeroto521 · Oct 28, 2025 · Oct 28, 2025 · Oct 28, 2025 · Nov 7, 2025
commit 64097ee34d85cc6e45a2191bd6ff9e86c63798c1
diff --git a/src/pyscipopt/expr.pxi b/src/pyscipopt/expr.pxi
@@ -91,14 +91,22 @@ class Expr:
    def __abs__(self) -> AbsExpr:
        return UnaryExpr.from_expr(self, AbsExpr)

+    @staticmethod
+    def _is_sum(expr: Expr) -> bool:
+        return type(expr) is Expr or isinstance(expr, PolynomialExpr)
+
    def __add__(self, other):
        other = Expr.from_const_or_var(other)
        if isinstance(other, Expr):
            if not self.children:
                return other
-            if isinstance(other, SumExpr):
-                return SumExpr(other.to_dict({self: 1.0}))
-            return SumExpr({self: 1.0, other: 1.0})
+            if Expr._is_sum(self):
+                if Expr._is_sum(other):
+                    return Expr(self.to_dict(other.children))
+                return Expr(self.to_dict({other: 1.0}))
+            elif Expr._is_sum(other):
+                return Expr(other.to_dict({self: 1.0}))
+            return Expr({self: 1.0, other: 1.0})
        elif isinstance(other, MatrixExpr):
            return other.__add__(self)
        raise TypeError(
@@ -226,8 +234,11 @@ class Expr:

        return res

+    def _remove_zero(self) -> dict:
+        return {k: v for k, v in self.children.items() if v != 0}
+
    def _normalize(self) -> Expr:
-        return self
+        return Expr(self._remove_zero())

    def degree(self) -> float:
        return max((i.degree() for i in self)) if self.children else float("inf")
@@ -249,33 +260,7 @@ class Expr:
        return nodes + [(type(self), indices)]


-class SumExpr(Expr):
-    """Expression like `expression1 + expression2 + constant`."""
-
-    def __add__(self, other):
-        other = Expr.from_const_or_var(other)
-        if isinstance(other, Expr):
-            if isinstance(other, SumExpr):
-                return SumExpr(self.to_dict(other.children))
-            return SumExpr(self.to_dict({other: 1.0}))
-        return super().__add__(other)
-
-    def __mul__(self, other):
-        other = Expr.from_const_or_var(other)
-        if isinstance(other, ConstExpr):
-            if other[CONST] == 0:
-                return ConstExpr(0.0)
-            return SumExpr({i: self[i] * other[CONST] for i in self if self[i] != 0})
-        return super().__mul__(other)
-
-    def _remove_zero(self) -> dict:
-        return {k: v for k, v in self.children.items() if v != 0}
-
-    def _normalize(self) -> SumExpr:
-        return SumExpr(self._remove_zero())
-
-
-class PolynomialExpr(SumExpr):
+class PolynomialExpr(Expr):
    """Expression like `2*x**3 + 4*x*y + constant`."""

    def __init__(self, children: Optional[dict[Term, float]] = None):
@@ -340,7 +325,7 @@ class PolynomialExpr(SumExpr):
            nodes += child._to_nodes(start + len(nodes), c)

        if len(nodes) > 1:
-            return nodes + [(SumExpr, list(range(start, start + len(nodes))))]
+            return nodes + [(Expr, list(range(start, start + len(nodes))))]
        return nodes



diff --git a/src/pyscipopt/scip.pxi b/src/pyscipopt/scip.pxi
@@ -5690,8 +5690,7 @@ cdef class Model:
                PY_SCIP_CALL(SCIPcreateExprVar(self._scip, &scip_exprs[i], wrapper.ptr[0], NULL, NULL))
            elif e_type is ConstExpr:
                PY_SCIP_CALL(SCIPcreateExprValue(self._scip, &scip_exprs[i], <SCIP_Real>value, NULL, NULL))
-
-            elif e_type is SumExpr:
+            elif e_type is Expr:
                nchildren = len(value)
                children_expr = <SCIP_EXPR**> malloc(nchildren * sizeof(SCIP_EXPR*))
                coefs = <SCIP_Real*> malloc(nchildren * sizeof(SCIP_Real))