correct comments in group_norm_op (#19621)

Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/19621

Comments for group_norm_op is not accurate (i.e., the math part), this diff will fix it.

Reviewed By: BIT-silence

Differential Revision: D15048695

fbshipit-source-id: 27d41d3ae21054257967815254134849944d56ca

diff --git a/caffe2/operators/group_norm_op.cc b/caffe2/operators/group_norm_op.cc
index 80c01528287bf905cae38716d4e9166e17517e95..872462450f02ac301875c92c4df2f0d5d54290e3 100644 (file)
--- a/caffe2/operators/group_norm_op.cc
+++ b/caffe2/operators/group_norm_op.cc
@@ -15,12 +15,12 @@ namespace caffe2 {
 // Math:
 // Y = gamma * (X - mu) * rsig + beta
 // let s = gamma * rsig
-// let b = beta - mu * rsig
+// let b = beta - gamma * mu * rsig
 // Y = s * X + b
 // let n = K * HxW
 // dL/dX = dL/dY * dY/dX = dL/dY * (d(s * X)/dX + db/dX)
 // d(s * X)/dX = s + X * ds/dX = s + gamma * X * drsig/dX
-// db/dX = -u * drsig/dX - rsig * dmu/dX
+// db/dX = -gamma * u * drsig/dX - gamma * rsig * dmu/dX
 // drsig/dX = -rsig^3 * (X - mu) / n
 // dmu/dX = 1 / n
 

diff --git a/caffe2/operators/group_norm_op.cu b/caffe2/operators/group_norm_op.cu
index 3e1dcf5c15dea8eef57c00c34d2a75d56c2217b4..4e498adba960c0b300bc5ad31b008a4e4e210c57 100644 (file)
--- a/caffe2/operators/group_norm_op.cu
+++ b/caffe2/operators/group_norm_op.cu
@@ -139,12 +139,12 @@ __global__ void ComputeInternalGradientsNCHWCUDAKernel(
 // Math:
 // Y = gamma * (X - mu) * rsig + beta
 // let s = gamma * rsig
-// let b = beta - mu * rsig
+// let b = beta - gamma * mu * rsig
 // Y = s * X + b
 // let n = K * HxW
 // dL/dX = dL/dY * dY/dX = dL/dY * (d(s * X)/dX + db/dX)
 // d(s * X)/dX = s + X * ds/dX = s + gamma * X * drsig/dX
-// db/dX = -u * drsig/dX - rsig * dmu/dX
+// db/dX = -gamma * u * drsig/dX - gamma * rsig * dmu/dX
 // drsig/dX = -rsig^3 * (X - mu) / n
 // dmu/dX = 1 / n
 template <typename T>