Align mlx::core::min op nan propagation with NumPy (#2346)

mlx/backend/cpu/reduce.cpp

@@ -350,7 +350,15 @@ struct MinReduce {
   };
 
   template <int N, typename T>
-  T operator()(simd::Simd<T, N> x) {
+  std::enable_if_t<std::is_integral_v<T>, T> operator()(simd::Simd<T, N> x) {
+    return simd::min(x);
+  };
+
+  template <int N, typename T>
+  std::enable_if_t<!std::is_integral_v<T>, T> operator()(simd::Simd<T, N> x) {
+    if (simd::any(x != x)) {
+      return static_cast<T>(NAN);
+    }
     return simd::min(x);
   };
 };

mlx/backend/metal/kernels/reduction/ops.h

@@ -164,7 +164,15 @@ struct Min {
   DEFINE_SIMD_REDUCE()
 
   template <typename T>
-  T simd_reduce_impl(T val) {
+  metal::enable_if_t<metal::is_integral_v<T>, T> simd_reduce_impl(T val) {
+    return simd_min(val);
+  }
+
+  template <typename T>
+  metal::enable_if_t<!metal::is_integral_v<T>, T> simd_reduce_impl(T val) {
+    if (simd_any(val != val)) {
+      return static_cast<T>(NAN);
+    }
     return simd_min(val);
   }
 
@@ -176,11 +184,38 @@ struct Min {
   }
 
   // Operator
-  U operator()(U a, U b) {
+  template <typename T>
+  metal::enable_if_t<metal::is_integral_v<T>, T> operator()(T a, T b) {
     return a < b ? a : b;
   }
-};
 
+  template <typename T>
+  metal::enable_if_t<!metal::is_integral_v<T>, T> operator()(T a, T b) {
+    if (metal::isnan(a) || metal::isnan(b)) {
+      return static_cast<T>(NAN);
+    } else {
+      return a < b ? a : b;
+    }
+  }
+
+  template <>
+  complex64_t operator()(complex64_t a, complex64_t b) {
+    bool real_is_nan = metal::isnan(a.real) || metal::isnan(b.real);
+    bool imag_is_nan = metal::isnan(a.imag) || metal::isnan(b.imag);
+
+    if (!real_is_nan && !imag_is_nan) {
+      return a < b ? a : b;
+    } else if (real_is_nan && !imag_is_nan) {
+      return complex64_t(
+          static_cast<float>(NAN), a.imag < b.imag ? a.imag : b.imag);
+    } else if (!real_is_nan && imag_is_nan) {
+      return complex64_t(
+          a.real < b.real ? a.real : b.real, static_cast<float>(NAN));
+    } else {
+      return complex64_t(static_cast<float>(NAN), static_cast<float>(NAN));
+    }
+  };
+};
 template <typename U>
 struct Max {
   DEFINE_SIMD_REDUCE()