feat: CP support for mamba layer

[kmehant]

In this PR, we add CP support for mamba by swapping the HF mamba module with cp implementation from.

Results

Legend

abbreviation	meaning
cp	context parallel degree
ep	expert parallel degree
dp	data parallel degree
gas	gradient accumulation steps
ebs	effective batch size
s	sequence length is

Ablations

Parity Experiments

model	experiment setting	loss	tps per gpu
ibm-granite/granite-4.0-h-tiny	cp8-ebs4-s8192-gas1	0.8059140625	973.6
ibm-granite/granite-4.0-h-tiny	cp8-ebs4-s8192-gas1-ep8	0.80224609375	2367.6
ibm-granite/granite-4.0-h-tiny	cp8-ebs4-s8192-gas2	0.8059765625	NA
ibm-granite/granite-4.0-h-tiny	cp4-dp2-ebs4-s8192-gas1	0.802953125	953.4
ibm-granite/granite-4.0-h-tiny	cp1-dp4-ep4-ebs4-s8192-gas1	0.7967056884765625	2576

Long Context (sequence length is 131072 (128k))

model	experiment setting	tps per gpu	GPU memory util ratio
ibm-granite/granite-4.0-h-tiny	cp8-ebs1-s131072-gas1-ep8	1462.8	0.5140136719
ibm-granite/granite-4.0-h-small	cp8-ebs1-s131072-gas1-ep8	682.7	0.9887207031

Training Resumption

settings used: mk-cp8-ebs4-s8192-gas1

Summary of external dependencies

fsdp2-nov https://github.com/kmehant/transformers.git (additional changes not in upstream)

Changes:

1. Preparing batches to be compatible for CP if CP is enabled.
2. Wrapping training loop with torch cp context
3. Preparing shift labels for correct loss calculation
4. Specific loss reduction when combination of cp and dp is used.
5. model saving fix

fsdp2-fix https://github.com/kmehant/accelerate.git (additional changes not in upstream)

Changes:

1. Mixed precision fix when using FSDP2

fsdp2-fix https://github.com/kmehant/accelerate.git (additional changes not in upstream)

Changes:

1. Mixed precision fix when using FSDP2

mamba-cp https://github.com/kmehant/fms-acceleration.git (will be main after merging #164)

1. Enables CP for mamba layers to go hand in hand with self attention CP

mamba-cp https://github.com/garrett361/mamba (Thanks to Garrett)

1. Mamba_ssm kernels must be installed from this fork and branch to leverage CP.

Summary of PR merged into HF repos to enable CP and FSDP2.

1. feat: add ignored_params support for fsdp2 huggingface/accelerate#3731
2. fix: CPU RAM efficient loading for nd or HSDP parallelisms huggingface/accelerate#3740
3. feat: allow mixed precision policy as dtype huggingface/accelerate#3751
4. refactor: nit change for get_parameters_from_modules (code debt) huggingface/accelerate#3815
5. nit: needed sanity checks for fsdp2 huggingface/accelerate#3499
6. feat: support tensor parallel & Data loader huggingface/accelerate#3173 (dataloader part is reused for CP)
7. fix: fsdp sharded state dict wont work for save_only_model knob huggingface/transformers#36627

[ashokponkumar]

can we remove this?