test_fused_rope.py

# Copyright (c) 2022-2024, NVIDIA CORPORATION & AFFILIATES. All rights reserved.
#
# See LICENSE for license information.
import pytest
import torch
from typing import Callable, Dict, Tuple, Union
from transformer_engine.pytorch.attention import (
    RotaryPositionEmbedding,
    apply_rotary_pos_emb,
)


def apply_rotary_pos_emb_thd(
    t: torch.Tensor, cu_seqlens: torch.Tensor, freqs: torch.Tensor
) -> torch.Tensor:
    """A baseline implementation of applying RoPE for `thd` format.

    Args:
        t (Tensor): Input tensor T is of shape [t, h, d]
        cu_seqlens(Tensor):  Cumulative sum of sequence lengths in a batch for `t`,
        with shape [b + 1] and dtype torch.int32.
        freqs (Tensor): Rotary Positional embedding tensor freq is of shape [max_s, 1, 1, d]

    Returns:
        Tensor: Shape [t, h, d]. The input tensor after applying RoPE.
    """
    seqlens = (cu_seqlens[1:] - cu_seqlens[:-1]).tolist()
    return torch.cat(
        [apply_rotary_pos_emb(x.unsqueeze(1), freqs[: x.size(0)]) for x in torch.split(t, seqlens)]
    ).squeeze(1)


def get_tol(dtype: torch.dtype) -> Dict:
    if dtype == torch.bfloat16:
        return dict(atol=1e-2, rtol=1e-2)
    elif dtype == torch.float16:
        return dict(atol=1e-3, rtol=1e-3)
    return dict(atol=1e-5, rtol=1.3e-6)


# Gradient is a broadcasted scalar
def _overlapping_grad(output: torch.Tensor) -> torch.Tensor:
    return output.sum() * 2


# Gradient is a full tensor
def _non_overlapping_grad(output: torch.Tensor) -> torch.Tensor:
    t = torch.ones_like(output)
    return torch.sum(output * t)


@pytest.mark.parametrize("dtype", [torch.float32, torch.bfloat16, torch.float16])
@pytest.mark.parametrize("seq_length", [2048, 4096])
@pytest.mark.parametrize("hidden_size", [128, 256])
@pytest.mark.parametrize("rotary_percent", [0.5, 1.0])
@pytest.mark.parametrize("margin", [0, 10])
@pytest.mark.parametrize("transpose", [None, (0, 1), (2, 3)])
@pytest.mark.parametrize("tensor_format", ["sbhd", "bshd"])
@pytest.mark.parametrize("loss_func", [_overlapping_grad, _non_overlapping_grad])
def test_fused_rope(
    dtype: torch.dtype,
    seq_length: int,
    hidden_size: int,
    rotary_percent: float,
    margin: int,
    transpose: Union[Tuple, None],
    tensor_format: str,
    loss_func: Callable,
) -> None:
    device = torch.device("cuda:0")
    batch_size, head_num = 2, 64
    t = torch.rand(
        (seq_length - margin, batch_size, head_num, hidden_size),
        dtype=dtype,
        device=device,
    )
    if tensor_format == "bshd":
        t = t.transpose(0, 1).contiguous()
    if transpose:
        t = t.transpose(*transpose).contiguous().transpose(*transpose)
    t.requires_grad = True

    rotary_pos_emb = RotaryPositionEmbedding(hidden_size, rotary_percent)
    emb = rotary_pos_emb(seq_length)

    # unfused
    output_unfused = apply_rotary_pos_emb(t, emb, tensor_format=tensor_format, fused=False)
    loss_unfused = loss_func(output_unfused)
    loss_unfused.backward()
    grad_unfused = t.grad.detach().clone()
    t.grad = None

    # fused
    output_fused = apply_rotary_pos_emb(
        t,
        emb,
        tensor_format=tensor_format,
        fused=True,
    )
    loss_fused = loss_func(output_fused)
    loss_fused.backward()
    grad_fused = t.grad.detach().clone()
    t.grad = None

    torch.testing.assert_close(output_fused, output_unfused, **get_tol(dtype))
    torch.testing.assert_close(grad_fused, grad_unfused, **get_tol(dtype))
    assert output_fused.is_contiguous()


@pytest.mark.parametrize("dtype", [torch.float32, torch.bfloat16, torch.float16])
@pytest.mark.parametrize("hidden_size", [128, 256])
@pytest.mark.parametrize("rotary_percent", [0.5, 1.0])
@pytest.mark.parametrize("transpose", [None, (1, 2)])
@pytest.mark.parametrize("loss_func", [_overlapping_grad, _non_overlapping_grad])
def test_fused_rope_thd(
    dtype: torch.dtype,
    hidden_size: int,
    rotary_percent: float,
    transpose: Union[Tuple, None],
    loss_func: Callable,
) -> None:
    device = torch.device("cuda:0")
    batch_size, head_num = 2, 64
    cu_seqlens = torch.tensor(
        [0, 400, 542, 711, 727, 752, 1270, 1426, 1450, 1954, 2044, 2048],
        dtype=torch.int32,
        device=device,
    )
    t = torch.rand(
        (cu_seqlens[-1], head_num, hidden_size),
        dtype=dtype,
        device=device,
    )
    if transpose:
        t = t.transpose(*transpose).contiguous().transpose(*transpose)
    t.requires_grad = True

    rotary_pos_emb = RotaryPositionEmbedding(hidden_size, rotary_percent)
    emb = rotary_pos_emb(cu_seqlens[-1])

    # unfused
    output_unfused = apply_rotary_pos_emb_thd(t, cu_seqlens, emb)
    loss_unfused = loss_func(output_unfused)
    loss_unfused.backward()
    grad_unfused = t.grad.detach().clone()
    t.grad = None

    # fused
    output_fused = apply_rotary_pos_emb(
        t, emb, fused=True, tensor_format="thd", cu_seqlens=cu_seqlens
    )
    loss_fused = loss_func(output_fused)
    loss_fused.backward()
    grad_fused = t.grad.detach().clone()
    t.grad = None

    torch.testing.assert_close(output_fused, output_unfused, **get_tol(dtype))
    torch.testing.assert_close(grad_fused, grad_unfused, **get_tol(dtype))