Implement mlx.core.blackman (#3136)

mlx/ops.cpp

@@ -2346,6 +2346,33 @@ array hamming(int M, StreamOrDevice s /* = {} */) {
   return subtract(left_coef, multiply(right_coef, cos_vals, s), s);
 }
 
+array blackman(int M, StreamOrDevice s /* = {} */) {
+  if (M < 1) {
+    return array({});
+  }
+  if (M == 1) {
+    return ones({1}, float32, s);
+  }
+
+  auto n = arange(0, M, float32, s);
+
+  float arg_val = (2.0 * M_PI) / (M - 1);
+  auto x = multiply(array(arg_val, float32), n, s);
+
+  auto cos_x = cos(x, s);
+
+  auto alpha = array(0.34f, float32);
+  auto beta = array(0.5f, float32);
+  auto gamma = array(0.16f, float32);
+
+  auto term1 = multiply(beta, cos_x, s);
+
+  auto cos_sq = square(cos_x, s);
+  auto term2 = multiply(gamma, cos_sq, s);
+
+  return add(subtract(alpha, term1, s), term2, s);
+}
+
 /** Returns a sorted copy of the flattened array. */
 array sort(const array& a, StreamOrDevice s /* = {} */) {
   int size = a.size();

mlx/ops.h

@@ -672,6 +672,9 @@ MLX_API array hanning(int M, StreamOrDevice s = {});
 /** Returns the Hamming window of size M. */
 MLX_API array hamming(int M, StreamOrDevice s = {});
 
+/** Returns the Blackmann window of size M. */
+MLX_API array blackman(int M, StreamOrDevice s = {});
+
 /** Returns the index of the minimum value in the array. */
 MLX_API array argmin(const array& a, bool keepdims, StreamOrDevice s = {});
 inline array argmin(const array& a, StreamOrDevice s = {}) {

python/src/ops.cpp

@@ -1475,6 +1475,30 @@ void init_ops(nb::module_& m) {
                    appears only if the number of samples is odd).
     )pbdoc");
   m.def(
+      "blackman",
+      &mlx::core::blackman,
+      "M"_a,
+      nb::kw_only(),
+      "stream"_a = nb::none(),
+      nb::sig(
+          "def blackman(M: int, *, stream: Union[None, Stream, Device] = None) -> array"), // <--- J'ai rajouté ça
+      R"pbdoc(
+        Return the Blackman window.
+        
+        The Blackman window is a taper formed by using the first three terms of a summation of cosines.
+
+        .. math::
+          w(n) = 0.42 - 0.5 \cos\left(\frac{2\pi n}{M-1}\right) + 0.08 \cos\left(\frac{4\pi n}{M-1}\right)
+           \qquad 0 \le n \le M-1
+        
+        Args:
+            M (int): Number of points in the output window.
+            
+        Returns:
+            array: The window, with the maximum value normalized to one (the value one
+                   appears only if the number of samples is odd).
+    )pbdoc");
+  m.def(
       "linspace",
       [](Scalar start,
          Scalar stop,

python/tests/test_ops.py

@@ -1474,6 +1474,18 @@ class TestOps(mlx_tests.MLXTestCase):
         self.assertEqual(a.size, 0)
         self.assertEqual(a.dtype, mx.float32)
 
+    def test_blackman_general(self):
+        a = mx.blackman(10)
+        expected = np.blackman(10)
+        self.assertTrue(np.allclose(a, expected, atol=1e-5))
+
+        a = mx.blackman(1)
+        self.assertEqual(a.item(), 1.0)
+
+        a = mx.blackman(0)
+        self.assertEqual(a.size, 0)
+        self.assertEqual(a.dtype, mx.float32)
+
     def test_unary_ops(self):
         def test_ops(npop, mlxop, x, y, atol, rtol):
             r_np = npop(x)