[Feature] Zigzag Ring attention (#5905)

* halfway

* fix cross-PP-stage position id length diff bug

* fix typo

* fix typo

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* unified cross entropy func for all shardformer models

* remove redundant lines

* add basic ring attn; debug cross entropy

* fwd bwd logic complete

* fwd bwd logic complete; add experimental triton rescale

* precision tests passed

* precision tests passed

* fix typos and remove misc files

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* add sp_mode to benchmark; fix varlen interface

* update softmax_lse shape by new interface

* change tester name

* remove buffer clone; support packed seq layout

* add varlen tests

* fix typo

* all tests passed

* add dkv_group; fix mask

* remove debug statements

---------

Co-authored-by: Edenzzzz <wtan45@wisc.edu>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

tests/test_checkpoint_io/test_gemini_checkpoint_io.py

@@ -74,7 +74,7 @@ def exam_state_dict_with_origin(placement_config, model_name, use_safetensors: b
 @clear_cache_before_run()
 @parameterize("placement_config", OPTIM_PLACEMENT_CONFIGS)
 @parameterize("shard", [True, False])
-@parameterize("model_name", ["transformers_llama_for_casual_lm"])
+@parameterize("model_name", ["transformers_llama_for_causal_lm"])
 @parameterize("size_per_shard", [32])
 @parameterize("tp_size", [1, 2])
 @parameterize("zero_size", [2])