120 lines
5.2 KiB
Python
120 lines
5.2 KiB
Python
# Run test with:
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# torchrun --no_python --nproc_per_node=8 pytest -q -s tests/modules/test_mha_parallel.py
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import math
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import torch
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import torch.nn.functional as F
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import pytest
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from einops import rearrange
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from apex.transformer import parallel_state
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from apex.transformer import tensor_parallel
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from flash_attn.modules.mha import MHA, ParallelMHA
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is_sm8x = torch.cuda.get_device_capability('cuda')[0] >= 8
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@pytest.mark.parametrize('dtype', [torch.float16] + ([torch.bfloat16] if is_sm8x else []))
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# @pytest.mark.parametrize('dtype', [torch.float16])
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@pytest.mark.parametrize('world_size', [1, 2, 4, 8])
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# @pytest.mark.parametrize('world_size', [2])
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@pytest.mark.parametrize('sequence_parallel', [True, False])
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# @pytest.mark.parametrize('sequence_parallel', [False])
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@pytest.mark.parametrize('head_dim', [64, 128])
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# @pytest.mark.parametrize('head_dim', [64])
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@pytest.mark.parametrize('embed_dim', [1024, 4096])
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# @pytest.mark.parametrize('embed_dim', [1024])
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def test_mha_parallel(embed_dim, head_dim, sequence_parallel, world_size, dtype):
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assert embed_dim % head_dim == 0
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num_heads = embed_dim // head_dim
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assert num_heads % world_size == 0
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rtol, atol = (3e-3, 1e-2) if dtype == torch.bfloat16 else (3e-3, 1e-3)
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if not torch.distributed.is_initialized():
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torch.distributed.init_process_group(backend='nccl', init_method='env://')
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device = f'cuda:{torch.distributed.get_rank()}'
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assert world_size <= torch.distributed.get_world_size()
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parallel_state.initialize_model_parallel(tensor_model_parallel_size_=world_size)
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rank = parallel_state.get_tensor_model_parallel_rank()
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# set seed
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torch.random.manual_seed(0)
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batch_size = 2
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seqlen = 1024
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assert (batch_size * seqlen) % world_size == 0
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x_pt = torch.randn(batch_size * seqlen, embed_dim, device=device, dtype=dtype,
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requires_grad=True)
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# We need to generate g here so that all processes get the same gradient,
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# as rank 0 will have an extra bias that changes the RNG.
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# If we don't divide by batch_size, the gradient gets a bit too large.
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g = torch.randn_like(x_pt) / 32
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if sequence_parallel:
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x = tensor_parallel.scatter_to_sequence_parallel_region(x_pt).detach().clone().requires_grad_()
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else:
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x = x_pt.detach().clone().requires_grad_()
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model_pt = MHA(embed_dim, num_heads, rotary_emb_dim=int(head_dim // 2),
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use_flash_attn=True, device=device, dtype=dtype)
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partition_dim = embed_dim // world_size
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model = ParallelMHA(embed_dim, num_heads, parallel_state.get_tensor_model_parallel_group(),
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rotary_emb_dim=int(head_dim // 2), use_flash_attn=True,
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sequence_parallel=sequence_parallel, device=device, dtype=dtype)
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with torch.no_grad():
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model.Wqkv.weight.copy_(
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rearrange(rearrange(model_pt.Wqkv.weight, '(three o) i -> three o i', three=3)[:, rank * partition_dim:(rank + 1) * partition_dim],
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'three o i -> (three o) i')
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)
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model.Wqkv.bias.copy_(
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rearrange(rearrange(model_pt.Wqkv.bias, '(three o) -> three o', three=3)[:, rank * partition_dim:(rank + 1) * partition_dim],
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'three o -> (three o)')
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)
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model.out_proj.weight.copy_(
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model_pt.out_proj.weight[:, rank * partition_dim:(rank + 1) * partition_dim]
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)
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if rank == 0:
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model.out_proj.bias.copy_(model_pt.out_proj.bias)
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out = model(x, seqlen=seqlen)
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out_pt = rearrange(model_pt(rearrange(x_pt, '(b s) d -> b s d', s=seqlen)), 'b s d -> (b s) d')
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partition_batch_dim = batch_size * seqlen // world_size
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assert torch.allclose(
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out,
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out_pt[rank * partition_batch_dim:(rank + 1) * partition_batch_dim]
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if sequence_parallel else out_pt,
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rtol=rtol, atol=atol
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)
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out_pt.backward(g)
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out.backward(g[rank * partition_batch_dim:(rank + 1) * partition_batch_dim]
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if sequence_parallel else g)
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parallel_state.destroy_model_parallel()
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assert torch.allclose(
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x.grad,
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x_pt.grad[rank * partition_batch_dim:(rank + 1) * partition_batch_dim]
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if sequence_parallel else x_pt.grad,
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rtol=rtol, atol=atol / 100 # magnitude of x.grad is quite small
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)
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# The error for d_weight and d_bias is quite a bit higher
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assert torch.allclose(
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model.Wqkv.weight.grad,
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rearrange(rearrange(model_pt.Wqkv.weight.grad, '(three o) i -> three o i', three=3)[:, rank * partition_dim:(rank + 1) * partition_dim],
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'three o i -> (three o) i'),
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rtol=rtol, atol=atol * 10
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)
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assert torch.allclose(
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model.Wqkv.bias.grad,
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rearrange(rearrange(model_pt.Wqkv.bias.grad, '(three o) -> three o', three=3)[:, rank * partition_dim:(rank + 1) * partition_dim],
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'three o -> (three o)'),
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rtol=rtol, atol=atol * 5
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)
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assert torch.allclose(
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model.out_proj.weight.grad,
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model_pt.out_proj.weight.grad[:, rank * partition_dim:(rank + 1) * partition_dim],
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rtol=rtol, atol=atol * 10
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)
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if rank == 0:
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assert torch.allclose(model.out_proj.bias.grad, model_pt.out_proj.bias.grad, rtol=rtol, atol=atol * 5)
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