Speed up -ProdExpr and -Constant

CHANGELOG.md

@@ -11,7 +11,8 @@
 - Made `test_markDoNotAggrVar_and_getStatus` robust to SCIP presolve changes by discovering the aggregated/multi-aggregated variables instead of hardcoding them
 ### Changed
 - Move magic methods (`__radd__`, `__sub__`, `__rsub__`, `__rmul__`, `__richcmp__`, `__neg__`, and `__rtruediv__`) to `ExprLike` base class (#1204)
-- Speed up `Expr.__add__` and `Expr.__iadd__` via the C-level API
+- Speed up `Expr.__add__` and `Expr.__iadd__` via the C-level API (#1205)
+- Speed up `ProdExpr.__neg__` and `Constant.__neg__` via C-level API (#1250)
 - Extended `structured_optimization_trace` recipe to support context-managed JSONL tracing with final `run_end` records, alongside the existing attach-style in-memory tracing.
 ### Removed
 

src/pyscipopt/expr.pxi

@@ -767,6 +767,11 @@ cdef class ProdExpr(GenExpr):
         self.children = []
         self._op = Operator.prod
 
+    def __neg__(self, /) -> ProdExpr:
+        cdef ProdExpr res = self.copy(copy=True)
+        res.constant = -res.constant
+        return res
+
     def __repr__(self):
         return self._op + "(" + str(self.constant) + "," + ",".join(map(lambda child : child.__repr__(), self.children)) + ")"
 
@@ -850,11 +855,16 @@ cdef class UnaryExpr(GenExpr):
 
 # class for constant expressions
 cdef class Constant(GenExpr):
+
     cdef public number
+
     def __init__(self,number):
         self.number = number
         self._op = Operator.const
 
+    def __neg__(self, /) -> Constant:
+        return Constant(-self.number)
+
     def __repr__(self):
         return str(self.number)
 

src/pyscipopt/scip.pyi

@@ -252,6 +252,7 @@ class Conshdlr:
 class Constant(GenExpr):
     number: Incomplete
     def __init__(self, *args: Incomplete, **kwargs: Incomplete) -> None: ...
+    def __neg__(self, /) -> Constant: ...
     def __pow__(  # type: ignore[override]
         self, other: float | Constant, mod: Incomplete = ..., /
     ) -> Constant: ...
@@ -355,6 +356,7 @@ class ExprLike:
         **kwargs: Incomplete,
     ) -> Incomplete: ...
     def __pos__(self, /) -> Self: ...
+    def __neg__(self, /) -> ExprLike: ...
     def __abs__(self, /) -> UnaryExpr: ...
     def exp(self) -> UnaryExpr: ...
     def log(self) -> UnaryExpr: ...
@@ -444,7 +446,7 @@ class GenExpr(ExprLike):
     def __init__(self) -> None: ...
     def degree(self) -> Incomplete: ...
     def getOp(self) -> Incomplete: ...
-    def __neg__(self, /) -> ProdExpr: ...
+    def __neg__(self, /) -> ProdExpr | Constant: ...
     @overload
     def __add__(self, other: float | ExprLike, /) -> SumExpr: ...
     @overload
@@ -2127,6 +2129,7 @@ class Pricer:
 class ProdExpr(GenExpr):
     constant: Incomplete
     def __init__(self, *args: Incomplete, **kwargs: Incomplete) -> None: ...
+    def __neg__(self, /) -> ProdExpr: ...
 
 @disjoint_base
 class Prop:

tests/test_expr.py

@@ -4,7 +4,15 @@
 import pytest
 
 from pyscipopt import Model, cos, exp, log, quickprod, sin, sqrt
-from pyscipopt.scip import CONST, Expr, ExprCons, GenExpr, MatrixGenExpr
+from pyscipopt.scip import (
+    CONST,
+    Constant,
+    Expr,
+    ExprCons,
+    GenExpr,
+    MatrixGenExpr,
+    ProdExpr,
+)
 
 
 @pytest.fixture(scope="module")
@@ -594,3 +602,25 @@ def test_pos():
     e = +c
     assert str(e) == str(c)
     assert e is not c
+
+def test_neg():
+    m = Model()
+    x = m.addVar(name="x")
+
+    expr = (x + 1) ** 3
+    neg_expr = -expr
+    assert isinstance(expr, Expr)
+    assert isinstance(neg_expr, Expr)
+    assert (
+        str(neg_expr)
+        == "Expr({Term(x, x, x): -1.0, Term(x, x): -3.0, Term(x): -3.0, Term(): -1.0})"
+    )
+
+    base = sqrt(x)
+    expr = base * -1
+    neg_expr = -expr
+    assert isinstance(expr, ProdExpr)
+    assert isinstance(neg_expr, ProdExpr)
+    assert str(neg_expr) == "prod(1.0,sqrt(sum(0.0,prod(1.0,x))))"
+
+    assert str(-Constant(3.0)) == "-3.0"