Speed up PowExpr._evaluate via the C-level API

CHANGELOG.md

@@ -16,6 +16,8 @@
 - Refactor general expression conversion into per-class `to_scip_expr` recursion
 - Made expression fields read-only to prevent accidental runtime modification
 - Methods taking a list of variables (e.g. `addConsKnapsack()`) no longer convert it to a NumPy array to check its dimension
+- Speed up `PowExpr._evaluate` via the C-level API
+- `PowExpr._evaluate` now raises `ValueError("math domain error")` for a negative base with a non-integer exponent and `OverflowError` when the result overflows.
 ### Removed
 
 ## 6.3.0 - 2026.10.11

src/pyscipopt/expr.pxi

@@ -57,7 +57,9 @@ from cpython.tuple cimport PyTuple_GET_ITEM
 from libc.math cimport cos as c_cos
 from libc.math cimport exp as c_exp
 from libc.math cimport fabs as c_fabs
+from libc.math cimport floor as c_floor
 from libc.math cimport log as c_log
+from libc.math cimport pow as c_pow
 from libc.math cimport sqrt as c_sqrt
 from libc.math cimport sin as c_sin
 from libc.math cimport INFINITY
@@ -903,7 +905,17 @@ cdef class PowExpr(GenExpr):
         return expr
 
     cpdef double _evaluate(self, Solution sol) except *:
-        return (<GenExpr>self.children[0])._evaluate(sol) ** self.expo
+        cdef double base = (<GenExpr>self.children[0])._evaluate(sol)
+        cdef double expo = <double>self.expo
+        if base == 0.0 and expo < 0:
+            raise ZeroDivisionError("0.0 cannot be raised to a negative power")
+        elif base < 0.0 and expo != c_floor(expo):
+            raise ValueError("math domain error")
+
+        cdef double res = c_pow(base, expo)
+        if c_fabs(res) == INFINITY and c_fabs(base) != INFINITY and c_fabs(expo) != INFINITY:
+            raise OverflowError("math range error")
+        return res
 
     cdef PowExpr copy(self, bint copy=True):
         cdef PowExpr res = PowExpr.__new__(PowExpr)

tests/test_expr.py

@@ -256,7 +256,6 @@ def test_getVal_with_GenExpr():
     # sin and cos reject infinite arguments, like math.sin(inf)
     with pytest.raises(ValueError, match="math domain error"):
         m.getVal(sin(math.inf))
-
     with pytest.raises(ValueError, match="math domain error"):
         m.getVal(cos(-math.inf))
 
@@ -265,6 +264,28 @@ def test_getVal_with_GenExpr():
         m.getVal(exp(log(-x)))
 
 
+def test_getVal_pow():
+    m = Model()
+    y = m.addVar(lb=2, ub=2, name="y")
+    z = m.addVar(lb=0, ub=0, name="z")
+    n = m.addVar(lb=-2, ub=-2, name="n")
+    m.optimize()
+
+    # C-level pow with a negative exponent (matches Python: 2.0**-2.0 == 0.25)
+    assert m.getVal(y ** -2.0) == 0.25
+
+    # non-integer exponents are undefined for negative bases, like math.pow
+    with pytest.raises(ValueError, match="math domain error"):
+        m.getVal(n ** 0.5)
+
+    # zero to a negative power raises, like Python's 0.0**-1.0
+    with pytest.raises(ZeroDivisionError):
+        m.getVal(z ** -1.0)
+
+    with pytest.raises(OverflowError, match="math range error"):
+        m.getVal(exp(y) ** 10000.0)
+
+
 def test_unary_ufunc(model):
     m, x, y, z = model