From ee5cd128da2ad88f22cbe3b828132b2b2310b3f0 Mon Sep 17 00:00:00 2001
From: Yang Yu <yuyang18@baidu.com>
Date: Wed, 20 Dec 2017 14:16:44 +0800
Subject: [PATCH] Add comment of GetSubLoDAndAbsoluteOffset

---
 paddle/framework/lod_tensor.h | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/paddle/framework/lod_tensor.h b/paddle/framework/lod_tensor.h
index 9411c96aea4c1..0923c52a0ad2f 100644
--- a/paddle/framework/lod_tensor.h
+++ b/paddle/framework/lod_tensor.h
@@ -184,6 +184,18 @@ LoDTensor LodExpand(const LoDTensor& source, const LoD& lod, size_t level,
   return tensor;
 }
 
+// Get the absolute offset of a lod[start_level][start_idx:end_idx] and
+// relative length of details for every levels(i.e., [start_level: ]).
+//
+// For example,
+//   lod = [[0, 3, 4, 8], [0, 9, 10, 11, 13, 17, 19, 22, 24]]
+//   start_level = 0
+//   start_idx = 1
+//   end_idx = 3
+//
+// Returns:
+//  LoD = [[1, 4], [2, 4, 2, 3, 2]]
+//  pair<size_t, size_t> = {11, 24}
 std::pair<LoD, std::pair<size_t, size_t>> GetSubLoDAndAbsoluteOffset(
     const LoD& lod, size_t start_idx, size_t end_idx, size_t start_level);