From 8b8cf9e5cc3e4fa3ee7eb35cca685a399506d4a2 Mon Sep 17 00:00:00 2001
From: sunjiahao1999 <578431509@qq.com>
Date: Wed, 15 Feb 2023 16:11:08 +0800
Subject: [PATCH] add comments

---
 mmdet3d/datasets/transforms/formating.py | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/mmdet3d/datasets/transforms/formating.py b/mmdet3d/datasets/transforms/formating.py
index 1e1bce693..87661f7d9 100644
--- a/mmdet3d/datasets/transforms/formating.py
+++ b/mmdet3d/datasets/transforms/formating.py
@@ -155,6 +155,10 @@ def pack_single_results(self, results: dict) -> dict:
                 img = results['img']
                 if len(img.shape) < 3:
                     img = np.expand_dims(img, -1)
+                # To improve the computational speed by by 3-5 times, apply:
+                # `torch.permute()` rather than `np.transpose()`.
+                # Refer to https://github.com/open-mmlab/mmdetection/pull/9533
+                # for more details
                 results['img'] = to_tensor(img).permute(2, 0, 1).contiguous()
 
         for key in [