Merge pull request #30850 from charris/backport-30840

charris · web-flow · commit c5685a6b09e0 · 2026-02-18T19:48:09.000-07:00
BUG: Fix weak hash function in np.isin(). (#30840)
diff --git a/numpy/_core/src/multiarray/unique.cpp b/numpy/_core/src/multiarray/unique.cpp
@@ -63,7 +63,7 @@ empty_array_like(PyArrayObject *arr, npy_intp length)
 
 template <typename T>
 size_t hash_integer(const T *value, npy_bool equal_nan) {
-    return std::hash<T>{}(*value);
+    return npy_fnv1a(reinterpret_cast<const unsigned char*>(value), sizeof(T));
 }
 
 template <typename S, typename T, S (*real)(T), S (*imag)(T)>

Original file line number	Diff line number	Diff line change
`@@ -63,7 +63,7 @@ empty_array_like(PyArrayObject *arr, npy_intp length)`
`63`	`63`
`64`	`64`	`template <typename T>`
`65`	`65`	`size_t hash_integer(const T *value, npy_bool equal_nan) {`
`66`		`- return std::hash<T>{}(*value);`
	`66`	`+ return npy_fnv1a(reinterpret_cast<const unsigned char*>(value), sizeof(T));`
`67`	`67`	`}`
`68`	`68`
`69`	`69`	`template <typename S, typename T, S (real)(T), S (imag)(T)>`