Copy rotary from vortex; drop-in replace vortex.ops apply_rotary with flash_attn's apply_rotary

rotary.py

@@ -0,0 +1,547 @@
+# Copied verbatim from vortex
+# Copyright (c) 2023, Tri Dao.
+
+from typing import Optional, Tuple, Union
+
+import torch
+from einops import rearrange, repeat
+
+# Commenting this out from the original file in vortex; this is guaranteed to
+# fail since we're not shipping ops
+# from vortex.ops.embedding.rotary import apply_rotary
+# Instead, we use flash_attn ops completely following https://github.com/Dao-AILab/flash-attention/blob/main/flash_attn/layers/rotary.py
+from flash_attn.ops.triton.rotary import apply_rotary
+
+def rotate_half(x, interleaved=False):
+    if not interleaved:
+        x1, x2 = x.chunk(2, dim=-1)
+        return torch.cat((-x2, x1), dim=-1)
+    else:
+        x1, x2 = x[..., ::2], x[..., 1::2]
+        return rearrange(torch.stack((-x2, x1), dim=-1), "... d two -> ... (d two)", two=2)
+
+
+def apply_rotary_emb_torch(x, cos, sin, interleaved=False):
+    """
+    x: (batch_size, seqlen, nheads, headdim)
+    cos, sin: (seqlen, rotary_dim / 2) or (batch_size, seqlen, rotary_dim / 2)
+    """
+    ro_dim = cos.shape[-1] * 2
+    assert ro_dim <= x.shape[-1]
+    cos = repeat(cos, "... d -> ... 1 (2 d)" if not interleaved else "... d -> ... 1 (d 2)")
+    sin = repeat(sin, "... d -> ... 1 (2 d)" if not interleaved else "... d -> ... 1 (d 2)")
+    return torch.cat(
+        [
+            x[..., :ro_dim] * cos + rotate_half(x[..., :ro_dim], interleaved) * sin,
+            x[..., ro_dim:],
+        ],
+        dim=-1,
+    )
+
+
+class ApplyRotaryEmb(torch.autograd.Function):
+    @staticmethod
+    def forward(
+        ctx,
+        x,
+        cos,
+        sin,
+        interleaved=False,
+        inplace=False,
+        seqlen_offsets: Union[int, torch.Tensor] = 0,
+        cu_seqlens: Optional[torch.Tensor] = None,
+        max_seqlen: Optional[int] = None,
+    ):
+        out = apply_rotary(
+            x,
+            cos,
+            sin,
+            seqlen_offsets=seqlen_offsets,
+            cu_seqlens=cu_seqlens,
+            max_seqlen=max_seqlen,
+            interleaved=interleaved,
+            inplace=inplace,
+        )
+        if isinstance(seqlen_offsets, int):
+            ctx.save_for_backward(cos, sin, cu_seqlens)  # Can't save int with save_for_backward
+            ctx.seqlen_offsets = seqlen_offsets
+        else:
+            ctx.save_for_backward(cos, sin, cu_seqlens, seqlen_offsets)
+            ctx.seqlen_offsets = None
+        ctx.interleaved = interleaved
+        ctx.inplace = inplace
+        ctx.max_seqlen = max_seqlen
+        return out if not inplace else x
+
+    @staticmethod
+    def backward(ctx, do):
+        seqlen_offsets = ctx.seqlen_offsets
+        if seqlen_offsets is None:
+            cos, sin, cu_seqlens, seqlen_offsets = ctx.saved_tensors
+        else:
+            cos, sin, cu_seqlens = ctx.saved_tensors
+        # TD [2023-09-02]: For some reason Triton (2.0.0.post1) errors with
+        # "[CUDA]: invalid device context", and cloning makes it work. Idk why. Triton 2.1.0 works.
+        if not ctx.interleaved and not ctx.inplace:
+            do = do.clone()
+        dx = apply_rotary(
+            do,
+            cos,
+            sin,
+            seqlen_offsets=seqlen_offsets,
+            cu_seqlens=cu_seqlens,
+            max_seqlen=ctx.max_seqlen,
+            interleaved=ctx.interleaved,
+            inplace=ctx.inplace,
+            conjugate=True,
+        )
+        return dx, None, None, None, None, None, None, None
+
+
+def apply_rotary_emb(
+    x,
+    cos,
+    sin,
+    interleaved=False,
+    inplace=False,
+    seqlen_offsets: Union[int, torch.Tensor] = 0,
+    cu_seqlens: Optional[torch.Tensor] = None,
+    max_seqlen: Optional[int] = None,
+):
+    """
+    Arguments:
+        x: (batch_size, seqlen, nheads, headdim) if cu_seqlens is None
+            else (total_seqlen, nheads, headdim)
+        cos, sin: (seqlen_rotary, rotary_dim / 2)
+        interleaved: if True, rotate pairs of even and odd dimensions (GPT-J style) instead
+            of 1st half and 2nd half (GPT-NeoX style).
+        inplace: if True, apply rotary embedding in-place.
+        seqlen_offsets: (batch_size,) or int. Each sequence in x is shifted by this amount.
+            Most commonly used in inference when we have KV cache.
+        cu_seqlens: (batch + 1,) or None
+        max_seqlen: int
+    Return:
+        out: (batch_size, seqlen, nheads, headdim) if cu_seqlens is None
+            else (total_seqlen, nheads, headdim)
+    rotary_dim must be <= headdim
+    Apply rotary embedding to the first rotary_dim of x.
+    """
+    return ApplyRotaryEmb.apply(x, cos, sin, interleaved, inplace, seqlen_offsets, cu_seqlens, max_seqlen)
+
+
+# For backward compatibility
+apply_rotary_emb_func = apply_rotary_emb
+
+
+class ApplyRotaryEmbQKV_(torch.autograd.Function):
+    @staticmethod
+    def forward(
+        ctx,
+        qkv,
+        cos,
+        sin,
+        cos_k=None,
+        sin_k=None,
+        interleaved=False,
+        seqlen_offsets: Union[int, torch.Tensor] = 0,
+        num_heads_q: Union[int] = None,
+    ):
+        if cos_k is None and sin_k is None and qkv.is_contiguous():
+            # Call 1 kernel instead of 2 kernels
+            # We need qkv to be contiguous so that when we reshape to combine (3, nheads)
+            # dimensions, we get the same tensor
+            if qkv.dim() == 5:
+                batch, seqlen, three, nheads, headdim = qkv.shape
+                assert three == 3
+                # qk = rearrange(qkv[:, :, :2], "b s t h d -> b s (t h) d")
+                qk = qkv[:, :, :2].reshape(batch, seqlen, -1, headdim)
+            else:
+                assert qkv.dim() == 4
+                assert num_heads_q is not None
+                num_heads_k = (qkv.shape[2] - num_heads_q) // 2
+                assert qkv.shape[2] == num_heads_q + 2 * num_heads_k
+                qk = qkv[:, :, : num_heads_q + num_heads_k]
+            apply_rotary(
+                qk,
+                cos,
+                sin,
+                seqlen_offsets=seqlen_offsets,
+                interleaved=interleaved,
+                inplace=True,
+            )
+        else:
+            cos_k = cos if cos_k is None else cos_k
+            sin_k = sin if sin_k is None else sin_k
+            if qkv.dim() == 5:
+                q, k = qkv[:, :, 0], qkv[:, :, 1]
+            else:
+                assert qkv.dim() == 4
+                assert num_heads_q is not None
+                num_heads_k = (qkv.shape[2] - num_heads_q) // 2
+                assert qkv.shape[2] == num_heads_q + 2 * num_heads_k
+                q, k = (
+                    qkv[:, :, :num_heads_q],
+                    qkv[:, :, num_heads_q : num_heads_q + num_heads_k],
+                )
+            apply_rotary(q, cos, sin, seqlen_offsets, interleaved=interleaved, inplace=True)
+            apply_rotary(k, cos_k, sin_k, seqlen_offsets, interleaved=interleaved, inplace=True)
+            ctx.save_for_backward(cos, sin, cos_k, sin_k)
+        if isinstance(seqlen_offsets, int):
+            ctx.save_for_backward(cos, sin, cos_k, sin_k)
+            ctx.seqlen_offsets = seqlen_offsets
+        else:
+            ctx.save_for_backward(cos, sin, cos_k, sin_k, seqlen_offsets)
+            ctx.seqlen_offsets = None
+        ctx.interleaved = interleaved
+        ctx.num_heads_q = num_heads_q
+        return qkv
+
+    @staticmethod
+    def backward(ctx, dqkv):
+        seqlen_offsets = ctx.seqlen_offsets
+        if seqlen_offsets is None:
+            cos, sin, cos_k, sin_k, seqlen_offsets = ctx.saved_tensors
+        else:
+            cos, sin, cos_k, sin_k = ctx.saved_tensors
+        if cos_k is None and sin_k is None and dqkv.is_contiguous():
+            # Call 1 kernel instead of 2 kernels
+            # We need dqkv to be contiguous so that when we reshape to combine (3, nheads)
+            # dimensions, we get the same tensor
+            if dqkv.dim() == 5:
+                dqk = rearrange(dqkv[:, :, :2], "b s t h d -> b s (t h) d")
+            else:
+                assert dqkv.dim() == 4
+                assert ctx.num_heads_q is not None
+                num_heads_k = (dqkv.shape[2] - ctx.num_heads_q) // 2
+                assert dqkv.shape[2] == ctx.num_heads_q + 2 * num_heads_k
+                dqk = dqkv[:, :, : ctx.num_heads_q + num_heads_k]
+            apply_rotary(
+                dqk,
+                cos,
+                sin,
+                seqlen_offsets=seqlen_offsets,
+                interleaved=ctx.interleaved,
+                inplace=True,
+                conjugate=True,
+            )
+        else:
+            cos_k = cos if cos_k is None else cos_k
+            sin_k = sin if sin_k is None else sin_k
+            if dqkv.dim() == 5:
+                dq, dk = dqkv[:, :, 0], dqkv[:, :, 1]
+            else:
+                assert dqkv.dim() == 4
+                assert ctx.num_heads_q is not None
+                num_heads_k = (dqkv.shape[2] - ctx.num_heads_q) // 2
+                assert dqkv.shape[2] == ctx.num_heads_q + 2 * num_heads_k
+                dq = dqkv[:, :, : ctx.num_heads_q]
+                dk = dqkv[:, :, ctx.num_heads_q : ctx.num_heads_q + num_heads_k]
+            apply_rotary(
+                dq,
+                cos,
+                sin,
+                seqlen_offsets,
+                interleaved=ctx.interleaved,
+                inplace=True,
+                conjugate=True,
+            )
+            apply_rotary(
+                dk,
+                cos_k,
+                sin_k,
+                seqlen_offsets,
+                interleaved=ctx.interleaved,
+                inplace=True,
+                conjugate=True,
+            )
+        return dqkv, None, None, None, None, None, None, None
+
+
+def apply_rotary_emb_qkv_(
+    qkv,
+    cos,
+    sin,
+    cos_k=None,
+    sin_k=None,
+    interleaved=False,
+    seqlen_offsets: Union[int, torch.Tensor] = 0,
+    num_heads_q: Optional[int] = None,
+):
+    """
+    Arguments:
+        qkv: (batch_size, seqlen, 3, nheads, headdim) or (batch_size, seqlen, num_heads_q + 2 * num_heads_k, headdim).
+            If qkv has shape (batch_size, seqlen, num_heads_q + 2 * num_heads_k, headdim) (e.g. MQA / GQA),
+            then num_heads_q must be provided.
+        cos, sin: (seqlen, rotary_dim / 2)
+        cos_k, sin_k: (seqlen, rotary_dim / 2), optional
+        interleaved: if True, rotate pairs of even and odd dimensions (GPT-J style) instead of
+            1st half and 2nd half (GPT-NeoX style).
+        seqlen_offsets: (batch_size,) or int. Each sequence in Q and K is shifted by this amount.
+            Most commonly used in inference when we have KV cache.
+    Return:
+        qkv: (batch_size, seqlen, 3, nheads, headdim) or (batch_size, seqlen, num_heads_q + 2 * num_heads_k, headdim)
+    rotary_dim must be <= headdim
+    Apply rotary embedding *inplace* to the first rotary_dim of Q and K.
+    """
+    return ApplyRotaryEmbQKV_.apply(qkv, cos, sin, cos_k, sin_k, interleaved, seqlen_offsets, num_heads_q)
+
+
+class ApplyRotaryEmbKV_(torch.autograd.Function):
+    @staticmethod
+    def forward(
+        ctx,
+        kv,
+        cos,
+        sin,
+        interleaved=False,
+        seqlen_offsets: Union[int, torch.Tensor] = 0,
+    ):
+        batch, seqlen, two, nheads, headdim = kv.shape
+        assert two == 2
+        k = kv[:, :, 0]
+        apply_rotary(
+            k,
+            cos,
+            sin,
+            seqlen_offsets=seqlen_offsets,
+            interleaved=interleaved,
+            inplace=True,
+        )
+        if isinstance(seqlen_offsets, int):
+            ctx.save_for_backward(cos, sin)  # Can't save int with save_for_backward
+            ctx.seqlen_offsets = seqlen_offsets
+        else:
+            ctx.save_for_backward(cos, sin, seqlen_offsets)
+            ctx.seqlen_offsets = None
+        ctx.interleaved = interleaved
+        return kv
+
+    @staticmethod
+    def backward(ctx, dkv):
+        seqlen_offsets = ctx.seqlen_offsets
+        if seqlen_offsets is None:
+            cos, sin, seqlen_offsets = ctx.saved_tensors
+        else:
+            cos, sin = ctx.saved_tensors
+        apply_rotary(
+            dkv[:, :, 0],
+            cos,
+            sin,
+            seqlen_offsets=seqlen_offsets,
+            interleaved=ctx.interleaved,
+            inplace=True,
+            conjugate=True,
+        )
+        return dkv, None, None, None, None
+
+
+apply_rotary_emb_kv_ = ApplyRotaryEmbKV_.apply
+
+
+def apply_rotary_emb_kv_(
+    kv,
+    cos,
+    sin,
+    interleaved=False,
+    seqlen_offsets: Union[int, torch.Tensor] = 0,
+):
+    """
+    Arguments:
+        kv: (batch_size, seqlen, 2, nheads, headdim)
+        cos, sin: (seqlen, rotary_dim / 2)
+        interleaved: if True, rotate pairs of even and odd dimensions (GPT-J style) instead of
+            1st half and 2nd half (GPT-NeoX style).
+        seqlen_offsets: (batch_size,) or int. Each sequence in Q and K is shifted by this amount.
+            Most commonly used in inference when we have KV cache.
+    Return:
+        kv: (batch_size, seqlen, 2, nheads, headdim)
+    rotary_dim must be <= headdim
+    Apply rotary embedding *inplace* to the first rotary_dim of K.
+    """
+    return ApplyRotaryEmbKV_.apply(kv, cos, sin, interleaved, seqlen_offsets)
+
+
+class RotaryEmbedding(torch.nn.Module):
+    """
+    The rotary position embeddings from RoFormer_ (Su et. al).
+    A crucial insight from the method is that the query and keys are
+    transformed by rotation matrices which depend on the relative positions.
+
+    Other implementations are available in the Rotary Transformer repo_ and in
+    GPT-NeoX_, GPT-NeoX was an inspiration
+
+    .. _RoFormer: https://arxiv.org/abs/2104.09864
+    .. _repo: https://github.com/ZhuiyiTechnology/roformer
+    .. _GPT-NeoX: https://github.com/EleutherAI/gpt-neox
+
+    If scale_base is not None, this implements XPos (Sun et al., https://arxiv.org/abs/2212.10554).
+    A recommended value for scale_base is 512: https://github.com/HazyResearch/flash-attention/issues/96
+    Reference: https://github.com/sunyt32/torchscale/blob/main/torchscale/component/xpos_relative_position.py
+    """
+
+    def __init__(
+        self,
+        dim: int,
+        base=10000.0,
+        interleaved=False,
+        scale_base=None,
+        pos_idx_in_fp32=True,
+        device=None,
+    ):
+        """
+        interleaved: if True, rotate pairs of even and odd dimensions (GPT-J style) instead
+            of 1st half and 2nd half (GPT-NeoX style).
+        pos_idx_in_fp32: if True, the position indices [0.0, ..., seqlen - 1] are in fp32,
+            otherwise they might be in lower precision.
+            This option was added because previously (before 2023-07-02), when we construct
+            the position indices, we use the dtype of self.inv_freq. In most cases this would
+            be fp32, but if the model is trained in pure bf16 (not mixed precision), then
+            self.inv_freq would be bf16, and the position indices are also in bf16.
+            Because of the limited precision of bf16 (e.g. 1995.0 is rounded to 2000.0), the
+            embeddings for some positions will coincide.
+            To maintain compatibility with models previously trained in pure bf16,
+            we add this option.
+        """
+        super().__init__()
+        self.dim = dim
+        self.base = float(base)
+        self.pos_idx_in_fp32 = pos_idx_in_fp32
+        # Generate and save the inverse frequency buffer (non trainable)
+        inv_freq = self._compute_inv_freq(device)
+        self.register_buffer("inv_freq", inv_freq, persistent=False)
+        self.interleaved = interleaved
+        self.scale_base = scale_base
+        scale = (
+            (torch.arange(0, dim, 2, device=device, dtype=torch.float32) + 0.4 * dim) / (1.4 * dim)
+            if scale_base is not None
+            else None
+        )
+        self.register_buffer("scale", scale, persistent=False)
+
+        self._seq_len_cached = 0
+        self._cos_cached = None
+        self._sin_cached = None
+        self._cos_k_cached = None
+        self._sin_k_cached = None
+
+    def _compute_inv_freq(self, device=None):
+        return 1.0 / (self.base ** (torch.arange(0, self.dim, 2, device=device, dtype=torch.float32) / self.dim))
+
+    def _update_cos_sin_cache(self, seqlen, device=None, dtype=None):
+        # Reset the tables if the sequence length has changed,
+        # if we're on a new device (possibly due to tracing for instance),
+        # or if we're switching from inference mode to training
+        if (
+            seqlen > self._seq_len_cached
+            or self._cos_cached is None
+            or self._cos_cached.device != device
+            or self._cos_cached.dtype != dtype
+            or (self.training and self._cos_cached.is_inference())
+        ):
+            self._seq_len_cached = seqlen
+            # We want fp32 here, not self.inv_freq.dtype, since the model could be loaded in bf16
+            # And the output of arange can be quite large, so bf16 would lose a lot of precision.
+            # However, for compatibility reason, we add an option to use the dtype of self.inv_freq.
+            if self.pos_idx_in_fp32:
+                t = torch.arange(seqlen, device=device, dtype=torch.float32)
+                # We want fp32 here as well since inv_freq will be multiplied with t, and the output
+                # will be large. Having it in bf16 will lose a lot of precision and cause the
+                # cos & sin output to change significantly.
+                # We want to recompute self.inv_freq if it was not loaded in fp32
+                if self.inv_freq.dtype != torch.float32:
+                    inv_freq = self._compute_inv_freq(device=device)
+                else:
+                    inv_freq = self.inv_freq
+            else:
+                t = torch.arange(seqlen, device=device, dtype=self.inv_freq.dtype)
+                inv_freq = self.inv_freq
+            # Don't do einsum, it converts fp32 to fp16 under AMP
+            # freqs = torch.einsum("i,j->ij", t, self.inv_freq)
+            freqs = torch.outer(t, inv_freq)
+            if self.scale is None:
+                self._cos_cached = torch.cos(freqs).to(dtype)
+                self._sin_cached = torch.sin(freqs).to(dtype)
+            else:
+                power = (
+                    torch.arange(seqlen, dtype=self.scale.dtype, device=self.scale.device) - seqlen // 2
+                ) / self.scale_base
+                scale = self.scale.to(device=power.device) ** rearrange(power, "s -> s 1")
+                # We want the multiplication by scale to happen in fp32
+                self._cos_cached = (torch.cos(freqs) * scale).to(dtype)
+                self._sin_cached = (torch.sin(freqs) * scale).to(dtype)
+                self._cos_k_cached = (torch.cos(freqs) / scale).to(dtype)
+                self._sin_k_cached = (torch.sin(freqs) / scale).to(dtype)
+
+    def forward(
+        self,
+        qkv: torch.Tensor,
+        kv: Optional[torch.Tensor] = None,
+        seqlen_offset: Union[int, torch.Tensor] = 0,
+        max_seqlen: Optional[int] = None,
+        num_heads_q: Optional[int] = None,
+    ) -> Union[torch.Tensor, Tuple[torch.Tensor, torch.Tensor]]:
+        """
+        qkv: (batch, seqlen, 3, nheads, headdim) or (batch, seqlen, num_heads_q + 2 * num_heads_k, headdim)
+            if kv is none, else it's just q of shape (batch, seqlen, nheads, headdim).
+            If qkv has shape (batch, seqlen, num_heads_q + 2 * num_heads_k, headdim) (e.g. MQA / GQA),
+            then num_heads_q must be provided.
+        kv: (batch, seqlen, 2, nheads, headdim)
+        seqlen_offset: (batch_size,) or int. Each sequence in x is shifted by this amount.
+            Most commonly used in inference when we have KV cache.
+            If it's a tensor of shape (batch_size,), then to update the cos / sin cache, one
+            should pass in max_seqlen, which will update the cos / sin cache up to that length.
+        Apply rotary embedding *inplace* to qkv and / or kv.
+        """
+        seqlen = qkv.shape[1]
+        if max_seqlen is not None:
+            self._update_cos_sin_cache(max_seqlen, device=qkv.device, dtype=qkv.dtype)
+        elif isinstance(seqlen_offset, int):
+            self._update_cos_sin_cache(seqlen + seqlen_offset, device=qkv.device, dtype=qkv.dtype)
+        if kv is None:
+            if self.scale is None:
+                return apply_rotary_emb_qkv_(
+                    qkv,
+                    self._cos_cached,
+                    self._sin_cached,
+                    interleaved=self.interleaved,
+                    seqlen_offsets=seqlen_offset,
+                    num_heads_q=num_heads_q,
+                )
+            else:
+                return apply_rotary_emb_qkv_(
+                    qkv,
+                    self._cos_cached,
+                    self._sin_cached,
+                    self._cos_k_cached,
+                    self._sin_k_cached,
+                    interleaved=self.interleaved,
+                    seqlen_offsets=seqlen_offset,
+                    num_heads_q=num_heads_q,
+                )
+        else:
+            q = qkv
+            q = apply_rotary_emb_func(
+                q,
+                self._cos_cached,
+                self._sin_cached,
+                interleaved=self.interleaved,
+                inplace=True,
+                seqlen_offsets=seqlen_offset,
+            )
+            if self.scale is None:
+                kv = apply_rotary_emb_kv_(
+                    kv,
+                    self._cos_cached,
+                    self._sin_cached,
+                    interleaved=self.interleaved,
+                    seqlen_offsets=seqlen_offset,
+                )
+            else:
+                kv = apply_rotary_emb_kv_(
+                    kv,
+                    self._cos_k_cached,
+                    self._sin_k_cached,
+                    interleaved=self.interleaved,
+                    seqlen_offsets=seqlen_offset,
+                )
+            return q, kv