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[shardformer]: fix llama causal mask with sequence parallelism and no flash attention #6452

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[shardformer]: fix llama causal mask with sequence parallelism and no flash attention #6452

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8 changes: 8 additions & 0 deletions colossalai/shardformer/modeling/llama.py
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Original file line number Diff line number Diff line change
Expand Up @@ -8,6 +8,7 @@
from torch import nn
from torch.nn import BCEWithLogitsLoss, CrossEntropyLoss, MSELoss
from transformers.cache_utils import Cache, DynamicCache
from transformers.modeling_attn_mask_utils import _prepare_4d_causal_attention_mask
from transformers.modeling_outputs import (
BaseModelOutputWithPast,
CausalLMOutputWithPast,
Expand Down Expand Up @@ -139,6 +140,13 @@ def llama_model_forward(
is_causal=True,
invert=(sp_mode != "ring_attn"),
)
elif shard_config.enable_sequence_parallelism:
# the attention forward is replaced for sequence parallelism (see the policy), and it takes a 4d causal
# mask over the full sequence. `_update_causal_mask` returns None for sdpa without padding (relying on
# sdpa's is_causal), and on later pipeline stages `hidden_states` only holds the local part of the sequence
attn_kwargs: torch.Tensor = _prepare_4d_causal_attention_mask(
attention_mask, (batch_size, seq_length), hidden_states, past_seen_tokens
)
else:
attn_kwargs: torch.Tensor = self._update_causal_mask(
attention_mask, hidden_states, cache_position, past_key_values
Expand Down
40 changes: 40 additions & 0 deletions tests/test_shardformer/test_model/test_shard_llama.py
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Original file line number Diff line number Diff line change
Expand Up @@ -225,6 +225,46 @@ def check_forward_backward(model_fn, data_gen_fn, output_transform_fn, loss_fn,
"precision": "fp16",
"initial_scale": 1,
},
# sequence parallelism without flash attention, the replaced attention forward needs a 4d causal mask
{ # Ulysess
"tp_size": 1,
"pp_size": 1,
"sp_size": 2,
"num_microbatches": 1,
"enable_sequence_parallelism": True,
"sequence_parallelism_mode": "all_to_all",
"enable_flash_attention": False,
"use_lazy_init": True,
"zero_stage": 0,
"precision": "fp32",
"initial_scale": 1,
},
{ # Ulysess + PP
"tp_size": 1,
"pp_size": 2,
"sp_size": 2,
"num_microbatches": 2,
"enable_sequence_parallelism": True,
"sequence_parallelism_mode": "all_to_all",
"enable_flash_attention": False,
"use_lazy_init": True,
"zero_stage": 1,
"precision": "fp16",
"initial_scale": 1,
},
{ # TP + SP split_gather
"tp_size": 2,
"pp_size": 1,
"sp_size": 1,
"num_microbatches": 1,
"enable_sequence_parallelism": True,
"sequence_parallelism_mode": "split_gather",
"enable_flash_attention": False,
"use_lazy_init": True,
"zero_stage": 0,
"precision": "fp32",
"initial_scale": 1,
},
{
"tp_size": 2,
"pp_size": 1,
Expand Down