[triton] added copyright information for flash attention (#2835)

* [triton] added copyright information for flash attention

* polish code

LICENSE

@@ -201,17 +201,31 @@ Copyright 2021- HPC-AI Technology Inc. All rights reserved.
    See the License for the specific language governing permissions and
    limitations under the License.
 
-## Some of colossal-ai's code is derived from Alpa, which is subject to the following copyright notice:
+   ## Some of colossal-ai's code is derived from others projects, which is subject to the following copyright notice:
+
+   Copyright 2021 The Alpa team.
 
-Copyright 2021 The Alpa team.
    Licensed under the Apache License, Version 2.0 (the "License");
    you may not use this file except in compliance with the License.
    You may obtain a copy of the License at
 
-       https://github.com/alpa-projects/alpa/blob/979a45a3e6187df941ef4a4c4c6eea664527d68d/LICENSE
+         https://github.com/alpa-projects/alpa/blob/979a45a3e6187df941ef4a4c4c6eea664527d68d/LICENSE
 
    Unless required by applicable law or agreed to in writing, software
    distributed under the License is distributed on an "AS IS" BASIS,
    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    See the License for the specific language governing permissions and
    limitations under the License.
+
+   -------------------------------------------------
+
+   Copyright 2018-2020 Philippe Tillet
+   Copyright 2020-2022 OpenAI
+
+   Permission is hereby granted, free of charge, to any person obtaining
+   a copy of this software and associated documentation files
+   (the "Software"), to deal in the Software without restriction,
+   including without limitation the rights to use, copy, modify, merge,
+   publish, distribute, sublicense, and/or sell copies of the Software,
+   and to permit persons to whom the Software is furnished to do so,
+   subject to the following conditions:

colossalai/kernel/cuda_native/flash_attention.py

@@ -1,8 +1,12 @@
 """
-Fused Attention
+The triton-based flash attention implementation is copied from the OpenAI/triton repository
-===============
+
-This is a Triton implementation of the Flash Attention algorithm
+You can find the repository in Triton https://github.com/openai/triton
-(see: Dao et al., https://arxiv.org/pdf/2205.14135v2.pdf; Rabe and Staats https://arxiv.org/pdf/2112.05682v2.pdf; Triton https://github.com/openai/triton)
+You can find the source file in https://github.com/openai/triton/blob/main/python/tutorials/06-fused-attention.py
+
+Reference:
+1. Dao et al., https://arxiv.org/pdf/2205.14135v2.pdf
+2. Rabe and Staats https://arxiv.org/pdf/2112.05682v2.pdf
 """
 
 import math
@@ -56,7 +60,8 @@ except ImportError:
     print('please install xformers from https://github.com/facebookresearch/xformers')
 
 if HAS_TRITON:
-
+    # the following functions are adapted from the OpenAI Triton tutorial
+    # https://github.com/openai/triton/blob/main/python/tutorials/06-fused-attention.py
     @triton.jit
     def _fwd_kernel(
         Q,