From 3da0418f1de79c7c1f9dc8e68ac354bf38d1ce64 Mon Sep 17 00:00:00 2001
From: Jiacheng Huang <huangjiacheng0709@outlook.com>
Date: Fri, 25 Jul 2025 14:50:05 +0800
Subject: [PATCH] Add `layer_norm` operator

---
 src/ntops/kernels/layer_norm.py | 47 +++++++++++++++++++++++++++++++++
 src/ntops/torch.py              | 28 ++++++++++++++++++++
 tests/test_layer_norm.py        | 37 ++++++++++++++++++++++++++
 3 files changed, 112 insertions(+)
 create mode 100644 src/ntops/kernels/layer_norm.py
 create mode 100644 tests/test_layer_norm.py

diff --git a/src/ntops/kernels/layer_norm.py b/src/ntops/kernels/layer_norm.py
new file mode 100644
index 0000000..44d1694
--- /dev/null
+++ b/src/ntops/kernels/layer_norm.py
@@ -0,0 +1,47 @@
+import functools
+import math
+
+import ninetoothed.language as ntl
+from ninetoothed import Tensor
+
+from ntops.kernels.reduction import arrangement
+
+
+def application(input, weight, bias, eps, output, num_normalized_elements):
+    _mean = ntl.zeros(input.dtype.shape, dtype=ntl.float32)
+
+    for i in range(input.shape[0]):
+        _mean += ntl.cast(input[i], ntl.float32)
+
+    mean = ntl.sum(_mean, 0) / num_normalized_elements
+
+    _var = ntl.zeros(input.dtype.shape, dtype=ntl.float32)
+
+    for i in range(input.shape[0]):
+        diff = ntl.cast(input[i], ntl.float32) - mean
+        diff = ntl.where(input[i].offsets(-1) < input.source.shape[-1], diff, 0)
+        _var += diff * diff
+
+    var = ntl.sum(_var, 0) / num_normalized_elements
+
+    std = ntl.sqrt(var + eps)
+
+    for i in range(input.shape[0]):
+        output[i] = (ntl.cast(input[i], ntl.float32) - mean) / std * weight[i] + bias[i]
+
+
+def premake(ndim, normalized_shape, dtype=None, block_size=None):
+    dims = tuple(-(dim + 1) for dim in range(len(normalized_shape)))
+
+    arrangement_ = functools.partial(arrangement, dim=dims, block_size=block_size)
+
+    tensors = (
+        Tensor(ndim, other=0, dtype=dtype),
+        Tensor(ndim, dtype=dtype),
+        Tensor(ndim, dtype=dtype),
+        Tensor(0, dtype=dtype),
+        Tensor(ndim, dtype=dtype),
+        Tensor(0, dtype=dtype, constexpr=True, value=math.prod(normalized_shape)),
+    )
+
+    return arrangement_, application, tensors
diff --git a/src/ntops/torch.py b/src/ntops/torch.py
index 2a01960..497d24b 100644
--- a/src/ntops/torch.py
+++ b/src/ntops/torch.py
@@ -23,6 +23,7 @@
 import ntops.kernels.gt
 import ntops.kernels.isinf
 import ntops.kernels.isnan
+import ntops.kernels.layer_norm
 import ntops.kernels.le
 import ntops.kernels.lt
 import ntops.kernels.mm
@@ -256,6 +257,33 @@ def isnan(input):
     return output
 
 
+def layer_norm(input, normalized_shape, weight=None, bias=None, eps=1e-5):
+    if isinstance(normalized_shape, int):
+        normalized_shape = (normalized_shape,)
+
+    normalized_shape = tuple(normalized_shape)
+
+    if weight is None:
+        weight = torch.ones_like(input)
+    else:
+        weight = weight.expand_as(input)
+
+    if bias is None:
+        bias = torch.zeros_like(input)
+    else:
+        bias = bias.expand_as(input)
+
+    output = torch.empty_like(input)
+
+    kernel = _cached_make(
+        ntops.kernels.layer_norm.premake, input.ndim, normalized_shape
+    )
+
+    kernel(input, weight, bias, eps, output, math.prod(normalized_shape))
+
+    return output
+
+
 def mm(input, mat2, *, out=None):
     m, _ = input.shape
     _, n = mat2.shape
diff --git a/tests/test_layer_norm.py b/tests/test_layer_norm.py
new file mode 100644
index 0000000..3433e7d
--- /dev/null
+++ b/tests/test_layer_norm.py
@@ -0,0 +1,37 @@
+import random
+
+import pytest
+import torch
+
+import ntops.torch
+from tests.skippers import skip_if_cuda_not_available
+from tests.utils import generate_arguments
+
+
+@skip_if_cuda_not_available
+@pytest.mark.parametrize("eps", (1e-8, 1e-5, 1e-3))
+@pytest.mark.parametrize("bias_is_none", (False, True))
+@pytest.mark.parametrize("weight_is_none", (False, True))
+@pytest.mark.parametrize(*generate_arguments())
+def test_cuda(shape, dtype, atol, rtol, weight_is_none, bias_is_none, eps):
+    device = "cuda"
+
+    input = torch.randn(shape, dtype=dtype, device=device)
+    normalized_shape = shape[-random.randint(1, len(shape)) :]
+    if weight_is_none:
+        weight = None
+    else:
+        weight = torch.randn(normalized_shape, dtype=dtype, device=device)
+    if bias_is_none:
+        bias = None
+    else:
+        bias = torch.randn(normalized_shape, dtype=dtype, device=device)
+
+    ninetoothed_output = ntops.torch.layer_norm(
+        input, normalized_shape, weight=weight, bias=bias, eps=eps
+    )
+    reference_output = torch.nn.functional.layer_norm(
+        input, normalized_shape, weight=weight, bias=bias, eps=eps
+    )
+
+    assert torch.allclose(ninetoothed_output, reference_output, atol=atol, rtol=rtol)