Update losses.py

add cos sim

python/mlx/nn/losses.py

@@ -372,3 +372,49 @@ def log_cosh_loss(
     loss = mx.logaddexp(errors, -errors) - math.log(2)
 
     return _reduce(loss, reduction)
+
+
+def cosine_similarity_loss(
+    embeddings1: mx.array,
+    embeddings2: mx.array,
+    targets: mx.array,
+    eps: float = 1e-8,
+    margin: float = 0.0,
+    reduction: str = "none",
+) -> mx.array:
+    """
+    Computes the Cosine Similarity loss.
+
+    This loss function calculates the cosine of the angle between two vectors and is often used in 
+    tasks involving embeddings, such as natural language processing or image recognition.
+
+    .. math::
+
+        \text{Cosine Similarity Loss}(e_1, e_2, y) = 
+        \begin{cases} 
+        1 - \frac{e_1 \cdot e_2}{\|e_1\| \|e_2\|} & \text{if } y = 1 \\
+        \max(0, \frac{e_1 \cdot e_2}{\|e_1\| \|e_2\|} - \text{margin}) & \text{if } y = -1 
+        \end{cases}
+
+
+    Args:
+        embeddings1 (mx.array): Embeddings for the first set of samples.
+        embeddings2 (mx.array): Embeddings for the second set of samples.
+        targets (mx.array): The target values (cosine similarity between embeddings).
+        margin (float, optional): Margin for dissimilar pairs. Default: ``0.0``.
+        reduction (str, optional): Specifies the reduction to apply to the output:
+          ``'none'`` | ``'mean'`` | ``'sum'``. Default: ``'none'``.
+
+    Returns:
+        mx.array: The computed Cosine Similarity loss.
+    """
+    embeddings1_norm = mx.sqrt(mx.sum(mx.square(embeddings1), axis=1) + eps)
+    embeddings2_norm = mx.sqrt(mx.sum(mx.square(embeddings2), axis=1) + eps)
+
+    cos_similarity = mx.sum(embeddings1 * embeddings2, axis=1) / (
+        embeddings1_norm * embeddings2_norm
+    )
+    loss = mx.where(
+        targets == 1, 1 - cos_similarity, mx.maximum(0, cos_similarity - margin)
+    )
+    return _reduce(loss, reduction)