gpt2l-flash.yaml

# @package _global_
defaults:
  - /experiment/owt/gpt2m-flash.yaml
  - override /model/gpt2model: gpt2-large
  # TD [2022-08-03] Surprisingly it's faster to use the ZeRO optimizer than just AdamW.
  # Still, fairscale is even faster and uses less memory.
  # I think it's because Pytorch is using ZeRO stage 1 and fairscale is using ZeRO stage 2?
  # However, fairscale has issues with saving checkpoint (either OOM or very
  # slow since it goes through the CPU?). Fairscale says Pytorch ZeRO is the
  # upstream version of OSS
  # https://github.com/facebookresearch/fairscale/issues/937
  # Pytorch ZeRO as also very slow for saving checkpoints due to
  # consolidate_state_dict(), but I've fixed it to save separate checkpoint per GPU.
  - override /optimizer: adamw-zero

  # FusedAdam doesn't seem to speed things up here, time per global step
  # (i.e. batch size 512) on 8 A100s is around 2056ms for both AdamW and FusedAdam.
  # This could be because each GPU is only doing the optimizer step for 1 /
  # world_size of the parameters.
  # Maybe the bottleneck here is the NCCL call to exchange parameters (ZeRO).
  # - override /optimizer: adamw-apex-zero

# Can enable mlp_chekcpoint_lvl to fit batch_size 16 on A100 40GB
# model:
#   config:
#     # mlp_checkpoint_lvl: ${eval:"[1] * 18 + [2] * 18"}
#     mlp_checkpoint_lvl: 1

datamodule:
  # batch_size: 16
  batch_size: ${eval:"4 if ${train.gpu_mem} < 24 else (8 if ${train.gpu_mem} < 40 else 16)"}

trainer:
  # strategy: null
  # strategy: ${eval:"None if ${trainer.devices} == 1 else 'ddp_sharded'"}
  strategy:
    _target_: src.utils.ddp_zero1.DDPStrategyZero1
    find_unused_parameters: False
    gradient_as_bucket_view: True
  # TD [2022-08-03] Deepspeed makes the ppl curve go wild
  # strategy: deepspeed_stage_1