[shardformer] Sequence Parallelism Optimization (#5533)

* sequence parallel optimization

* validate sequence parallel in llama (code to be polished)

* shardformer api writing

* integrate sequence parallel in ShardFormer

* fix pp bugs and sp bugs for LlaMa model

* integrating ring-based sequence parallelism into ShardFormer

* [sequence parallelism]: Add fused megatron function

* integrating ring-based sequence parallelism into ShardFormer

---------

Co-authored-by: linsj20 <linsj20@mails.tsinghua.edu.cn>

* fix bugs when useing sp and flashattention together

* fix operation function name

* support flash attention for ulysses-style sp

* clarify sp process group

* fix compatibility bugs in moe plugin

* fix fused linear bugs

* fix linear layer test

* support gpt model all-to-all sp

* modify shard data dimension (meant to be dim=-1)

* support megtron-style sp and distributed attn for llama model

* [shardformer] add megatron sp to llama

* support llama7B 128k with distributed attention

* [shardformer] robustness enhancement

* add block attn

* sp mode 1: keep input as a complete sequence

* fix sp compatability

* finish sp mode 3 support for gpt

* using all_to_all_single when batch size is 1

* support mode 2 sp in gpt2 (#5)

* [shardformer] add megatron sp to llama

* support llama7B 128k with distributed attention

* [shardformer] robustness enhancement

* add block attn

* sp mode 1: keep input as a complete sequence

* fix sp compatability

* refactor ring implementation

* support mode 2 sp in gpt2

* polish code

* enable distributed attn mask when using sp mode 2 and 3 in llama

* automatically enable flash attn when using sp mode 2 and 3 in llama

* inplace attn mask

* add zero2 support for sequence parallel

* polish code

* fix bugs

* fix gemini checkpoint io

* loose tensor checking atol and rtol

* add comment

* fix llama layernorm grad

* fix zero grad

* fix zero grad

* fix conflict

* update split and gather auto grad func

* sequence parallel: inside text split (#6)

* polish code (part 1)

* polish code (part 2)

* polish code (part 2.5)

* polish code (part 3)

* sequence parallel: inside text split

* miscellaneous minor fixes

* polish code

* fix ulysses style ZeRO

* sequence parallel: inside text split

* miscellaneous minor fixes

* disaggregate sp group and dp group for  sp

* fix llama and gpt sp

* polish code

* move ulysses grad sync to ddp (#9)

* remove zero_stage and unbind the grad sync for alltoall sp

* add 2d group creation test

* move ulysses grad sync to ddp

* add 2d group creation test

* remove useless code

* change shard config not to enable sp when enable_all_optimizations

* add sp warnings for several model

* remove useless code

---------

Co-authored-by: linsj20 <linsj20@mails.tsinghua.edu.cn>

colossalai/zero/low_level/low_level_optim.py

@@ -79,6 +79,7 @@ class LowLevelZeroOptimizer(OptimizerWrapper):
         master_weights: bool = True,  # master weights
     ):
         super(LowLevelZeroOptimizer, self).__init__(optim=optimizer)
+
         self._dtype = self.optim.param_groups[0]["params"][0].dtype
         self._logger = get_dist_logger()
         self._verbose = verbose
@@ -494,7 +495,6 @@ class LowLevelZeroOptimizer(OptimizerWrapper):
         # clear reduced grads
         if self._overlap_communication:
             get_accelerator().synchronize()
-
         self.zero_grad()
 
     def backward_by_grad(self, tensor, grad):