Fix NumPy 2.0 compatibility: replace np.find_common_type with np.result_type - Replace deprecated np.find_common_type calls in SumLinearOperator and ProductLinearOperator - Use functools.reduce with np.result_type to achieve same functionality - Fixes AttributeError when using NumPy 2.0+

Author: bydeng01

src/probnum/linops/_arithmetic_fallbacks.py

@@ -97,9 +97,7 @@ def __init__(self, *summands: LinearOperator):
 
         super().__init__(
             shape=summands[0].shape,
-            dtype=np.find_common_type(
-                [summand.dtype for summand in self._summands], []
-            ),
+            dtype=functools.reduce(np.result_type, [summand.dtype for summand in self._summands]),
             matmul=lambda x: functools.reduce(
                 operator.add, (summand @ x for summand in self._summands)
             ),
@@ -190,7 +188,7 @@ def __init__(self, *factors: LinearOperator):
 
         super().__init__(
             shape=(self._factors[0].shape[0], self._factors[-1].shape[1]),
-            dtype=np.find_common_type([factor.dtype for factor in self._factors], []),
+            dtype=functools.reduce(np.result_type, [factor.dtype for factor in self._factors]),
             matmul=lambda x: functools.reduce(
                 lambda vec, op: op @ vec, reversed(self._factors), x
             ),