Test build for Torch 2.7

build/torch27-cxx11-cu126-x86_64-linux/flash_attn3/__init__.py

@@ -0,0 +1,17 @@
+from .flash_attn_interface import (
+    flash_attn_combine,
+    flash_attn_func,
+    flash_attn_qkvpacked_func,
+    flash_attn_varlen_func,
+    flash_attn_with_kvcache,
+    get_scheduler_metadata,
+)
+
+__all__ = [
+    "flash_attn_combine",
+    "flash_attn_func",
+    "flash_attn_qkvpacked_func",
+    "flash_attn_varlen_func",
+    "flash_attn_with_kvcache",
+    "get_scheduler_metadata",
+]

build/torch27-cxx11-cu126-x86_64-linux/flash_attn3/_flash_attn3_2e75662.abi3.so

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:c0302224ac29ba4773d926d4cb16c01c45a374c6dd61286aae1f423f2bf495ea
+size 838459544

build/torch27-cxx11-cu126-x86_64-linux/flash_attn3/_ops.py

@@ -0,0 +1,9 @@
+import torch
+from . import _flash_attn3_2e75662
+ops = torch.ops._flash_attn3_2e75662
+
+def add_op_namespace_prefix(op_name: str):
+    """
+    Prefix op by namespace.
+    """
+    return f"_flash_attn3_2e75662::{op_name}"

build/torch27-cxx11-cu126-x86_64-linux/flash_attn3/flash_attn_interface.py

@@ -0,0 +1,828 @@
+# Copyright (c) 2023, Tri Dao.
+
+from typing import Optional, Union
+
+import torch
+import torch.nn as nn
+
+from ._ops import ops as flash_attn_3_cuda
+
+def maybe_contiguous(x):
+    return x.contiguous() if x is not None and x.stride(-1) != 1 else x
+
+
+def _flash_attn_forward(
+        q,
+        k,
+        v,
+        k_new,
+        v_new,
+        qv,
+        out,
+        cu_seqlens_q,
+        cu_seqlens_k,
+        cu_seqlens_k_new,
+        seqused_q,
+        seqused_k,
+        max_seqlen_q,
+        max_seqlen_k,
+        page_table,
+        kv_batch_idx,
+        leftpad_k,
+        rotary_cos,
+        rotary_sin,
+        seqlens_rotary,
+        q_descale,
+        k_descale,
+        v_descale,
+        softmax_scale,
+        causal,
+        window_size=(-1, -1),
+        attention_chunk=0,
+        softcap=0.0,
+        rotary_interleaved=True,
+        scheduler_metadata=None,
+        num_splits=1,
+        pack_gqa=None,
+        sm_margin=0):
+    q, k, k_new, v_new = [maybe_contiguous(x) for x in (q, k, k_new, v_new)]
+    v = v.contiguous() if v.stride(-1) != 1 and v.stride(-3) != 1 else v
+    cu_seqlens_q, cu_seqlens_k, cu_seqlens_k_new = [
+        maybe_contiguous(x) for x in (cu_seqlens_q, cu_seqlens_k, cu_seqlens_k_new)
+    ]
+    seqused_q, seqused_k = [maybe_contiguous(x) for x in (seqused_q, seqused_k)]
+    page_table, kv_batch_idx, leftpad_k = [
+        maybe_contiguous(x) for x in (page_table, kv_batch_idx, leftpad_k)
+    ]
+    rotary_cos, rotary_sin = [maybe_contiguous(x) for x in (rotary_cos, rotary_sin)]
+    seqlens_rotary = maybe_contiguous(seqlens_rotary)
+    out, softmax_lse, *rest = flash_attn_3_cuda.fwd(
+        q,
+        k,
+        v,
+        k_new,
+        v_new,
+        qv,
+        out,
+        cu_seqlens_q,
+        cu_seqlens_k,
+        cu_seqlens_k_new,
+        seqused_q,
+        seqused_k,
+        max_seqlen_q,
+        max_seqlen_k,
+        page_table,
+        kv_batch_idx,
+        leftpad_k,
+        rotary_cos,
+        rotary_sin,
+        seqlens_rotary,
+        q_descale,
+        k_descale,
+        v_descale,
+        softmax_scale,
+        causal,
+        window_size[0],
+        window_size[1],
+        attention_chunk,
+        softcap,
+        rotary_interleaved,
+        scheduler_metadata,
+        num_splits,
+        pack_gqa,
+        sm_margin,
+    )
+    return out, softmax_lse, *rest
+
+
+def _flash_attn_backward(
+        dout,
+        q,
+        k,
+        v,
+        out,
+        softmax_lse,
+        cu_seqlens_q,
+        cu_seqlens_k,
+        sequed_q,
+        sequed_k,
+        max_seqlen_q,
+        max_seqlen_k,
+        dq,
+        dk,
+        dv,
+        softmax_scale,
+        causal,
+        window_size=(-1, -1),
+        softcap=0.0,
+        deterministic=False,
+        sm_margin=0,
+):
+    # dq, dk, dv are allocated by us so they should already be contiguous
+    dout, q, k, v, out = [maybe_contiguous(x) for x in (dout, q, k, v, out)]
+    dq, dk, dv, softmax_d, *rest = flash_attn_3_cuda.bwd(
+        dout,
+        q,
+        k,
+        v,
+        out,
+        softmax_lse,
+        dq,
+        dk,
+        dv,
+        cu_seqlens_q,
+        cu_seqlens_k,
+        sequed_q,
+        sequed_k,
+        max_seqlen_q,
+        max_seqlen_k,
+        softmax_scale,
+        causal,
+        window_size[0],
+        window_size[1],
+        softcap,
+        deterministic,
+        sm_margin,
+    )
+    return dq, dk, dv, softmax_d
+
+
+class FlashAttnQKVPackedFunc(torch.autograd.Function):
+    @staticmethod
+    def forward(
+        ctx,
+        qkv,
+        softmax_scale,
+        causal,
+        q_descale=None, k_descale=None, v_descale=None,
+        window_size=(-1, -1),
+        attention_chunk=0,
+        softcap=0.0,
+        deterministic=False,
+        num_heads_q=None,
+        sm_margin=0,
+    ):
+        if softmax_scale is None:
+            softmax_scale = qkv.shape[-1] ** (-0.5)
+        if qkv.dim() == 5:
+            assert qkv.shape[-3] == 3
+            q, k, v = qkv.unbind(dim=-3)
+        else:
+            assert qkv.dim() == 4
+            assert num_heads_q is not None
+            num_heads_k = (qkv.shape[2] - num_heads_q) // 2
+            assert num_heads_k * 2 + num_heads_q == qkv.shape[2]
+            q, k, v = qkv.split([num_heads_q, num_heads_k, num_heads_k], dim=-2)
+        out, softmax_lse, *rest = _flash_attn_forward(
+            q,
+            k,
+            v,
+            None, None,  # k_new, v_new
+            None,  # qv
+            None,  # out
+            None, None, None,   # cu_seqlens_q/k/k_new
+            None, None,   # seqused_q/k
+            None, None,   # max_seqlen_q/k
+            None, None, None,   # page_table, kv_batch_idx, leftpad_k,
+            None, None, None,  # rotary_cos/sin, seqlens_rotary
+            q_descale, k_descale, v_descale,
+            softmax_scale,
+            causal=causal,
+            window_size=window_size,
+            attention_chunk=attention_chunk,
+            softcap=softcap,
+            sm_margin=sm_margin,
+        )
+        # ctx.save_for_backward(q, k, v, out_padded, softmax_lse)
+        ctx.save_for_backward(q, k, v, out, softmax_lse)
+        ctx.softmax_scale = softmax_scale
+        ctx.causal = causal
+        ctx.window_size = window_size
+        ctx.attention_chunk = attention_chunk
+        ctx.softcap = softcap
+        ctx.deterministic = deterministic
+        ctx.ndim = qkv.dim()
+        ctx.sm_margin = sm_margin
+        # return out, softmax_lse
+        return out
+
+    @staticmethod
+    def backward(ctx, dout, *args):
+        q, k, v, out, softmax_lse = ctx.saved_tensors
+        assert ctx.attention_chunk == 0, "FA3 backward does not support attention_chunk"
+        if ctx.ndim == 5:
+            qkv_shape = q.shape[:-2] + (3, *q.shape[-2:])
+            dqkv = torch.empty(qkv_shape, dtype=q.dtype, device=q.device)
+            dq, dk, dv = dqkv.unbind(dim=-3)
+        else:
+            num_heads_q = q.shape[2]
+            num_heads_k = k.shape[2]
+            qkv_shape = q.shape[:-2] + (num_heads_q + num_heads_k * 2, *q.shape[-1:])
+            dqkv = torch.empty(qkv_shape, dtype=q.dtype, device=q.device)
+            dq, dk, dv = dqkv.split([num_heads_q, num_heads_k, num_heads_k], dim=-2)
+        _flash_attn_backward(
+            dout,
+            q,
+            k,
+            v,
+            out,
+            softmax_lse,
+            None, None, # cu_seqlens_q, cu_seqlens_k,
+            None, None, # sequed_q, sequed_k,
+            None, None, # max_seqlen_q, max_seqlen_k,
+            dq,
+            dk,
+            dv,
+            ctx.softmax_scale,
+            ctx.causal,
+            ctx.window_size,
+            ctx.softcap,
+            ctx.deterministic,
+            ctx.sm_margin,
+        )
+        dqkv = dqkv[..., : dout.shape[-1]]  # We could have padded the head dimension
+        return dqkv, None, None, None, None, None, None, None, None, None, None, None
+
+
+class FlashAttnFunc(torch.autograd.Function):
+
+    @staticmethod
+    def forward(
+        ctx,
+        q,
+        k,
+        v,
+        softmax_scale,
+        causal,
+        qv=None,
+        q_descale=None, k_descale=None, v_descale=None,
+        window_size=(-1, -1),
+        attention_chunk=0,
+        softcap=0.0,
+        num_splits=1,
+        pack_gqa=None,
+        deterministic=False,
+        sm_margin=0,
+    ):
+        if softmax_scale is None:
+            softmax_scale = (q.shape[-1] + (qv.shape[-1] if qv is not None else 0)) ** (-0.5)
+        # out, q, k, v, out_padded, softmax_lse = _flash_attn_forward(
+        out, softmax_lse, *rest = _flash_attn_forward(
+            q,
+            k,
+            v,
+            None, None,  # k_new, v_new
+            qv,  # qv
+            None,  # out
+            None, None, None,   # cu_seqlens_q/k/k_new
+            None, None,   # seqused_q/k
+            None, None,   # max_seqlen_q/k
+            None, None, None,   # page_table, kv_batch_idx, leftpad_k,
+            None, None, None,  # rotary_cos/sin, seqlens_rotary
+            q_descale, k_descale, v_descale,
+            softmax_scale,
+            causal=causal,
+            window_size=window_size,
+            attention_chunk=attention_chunk,
+            softcap=softcap,
+            num_splits=num_splits,
+            pack_gqa=pack_gqa,
+            sm_margin=sm_margin,
+        )
+        # ctx.save_for_backward(q, k, v, out_padded, softmax_lse)
+        ctx.save_for_backward(q, k, v, out, softmax_lse)
+        ctx.softmax_scale = softmax_scale
+        ctx.causal = causal
+        ctx.window_size = window_size
+        ctx.attention_chunk = attention_chunk
+        ctx.softcap = softcap
+        ctx.deterministic = deterministic
+        ctx.sm_margin = sm_margin
+        return out, softmax_lse
+
+    @staticmethod
+    def backward(ctx, dout, *args):
+        q, k, v, out, softmax_lse = ctx.saved_tensors
+        assert ctx.attention_chunk == 0, "FA3 backward does not support attention_chunk"
+        dq, dk, dv = torch.empty_like(q), torch.empty_like(k), torch.empty_like(v)
+        _flash_attn_backward(
+            dout,
+            q,
+            k,
+            v,
+            out,
+            softmax_lse,
+            None, None, # cu_seqlens_q, cu_seqlens_k,
+            None, None, # sequed_q, sequed_k,
+            None, None, # max_seqlen_q, max_seqlen_k,
+            dq,
+            dk,
+            dv,
+            ctx.softmax_scale,
+            ctx.causal,
+            ctx.window_size,
+            ctx.softcap,
+            ctx.deterministic,
+            ctx.sm_margin,
+        )
+        dq = dq[..., : q.shape[-1]]  # We could have padded the head dimension
+        dk = dk[..., : k.shape[-1]]
+        dv = dv[..., : v.shape[-1]]
+        return dq, dk, dv, None, None, None, None, None, None, None, None, None, None, None, None, None, None
+
+
+class FlashAttnVarlenFunc(torch.autograd.Function):
+
+    @staticmethod
+    def forward(
+        ctx,
+        q,
+        k,
+        v,
+        cu_seqlens_q,
+        cu_seqlens_k,
+        seqused_q,
+        seqused_k,
+        max_seqlen_q,
+        max_seqlen_k,
+        softmax_scale,
+        causal,
+        qv=None,
+        q_descale=None, k_descale=None, v_descale=None,
+        window_size=(-1, -1),
+        attention_chunk=0,
+        softcap=0.0,
+        num_splits=1,
+        pack_gqa=None,
+        deterministic=False,
+        sm_margin=0,
+    ):
+        if softmax_scale is None:
+            softmax_scale = (q.shape[-1] + (qv.shape[-1] if qv is not None else 0)) ** (-0.5)
+        # out, q, k, v, out_padded, softmax_lse = _flash_attn_varlen_forward(
+        out, softmax_lse, *rest = _flash_attn_forward(
+            q,
+            k,
+            v,
+            None, None,  # k_new, v_new
+            qv,  # qv
+            None,  # out
+            cu_seqlens_q,
+            cu_seqlens_k,
+            None,   # cu_seqlens_k_new
+            seqused_q,
+            seqused_k,
+            max_seqlen_q,
+            max_seqlen_k,
+            None, None, None,   # page_table, kv_batch_idx, leftpad_k,
+            None, None, None,  # rotary_cos/sin, seqlens_rotary
+            q_descale, k_descale, v_descale,
+            softmax_scale,
+            causal=causal,
+            window_size=window_size,
+            attention_chunk=attention_chunk,
+            softcap=softcap,
+            num_splits=num_splits,
+            pack_gqa=pack_gqa,
+            sm_margin=sm_margin,
+        )
+        # ctx.save_for_backward(q, k, v, out_padded, softmax_lse, cu_seqlens_q, cu_seqlens_k, seqused_q, seqused_k)
+        ctx.save_for_backward(q, k, v, out, softmax_lse, cu_seqlens_q, cu_seqlens_k, seqused_q, seqused_k)
+        ctx.max_seqlen_q = max_seqlen_q
+        ctx.max_seqlen_k = max_seqlen_k
+        ctx.softmax_scale = softmax_scale
+        ctx.causal = causal
+        ctx.window_size = window_size
+        ctx.attention_chunk = attention_chunk
+        ctx.softcap = softcap
+        ctx.deterministic = deterministic
+        ctx.sm_margin = sm_margin
+        return out, softmax_lse
+
+    @staticmethod
+    def backward(ctx, dout, *args):
+        q, k, v, out, softmax_lse, cu_seqlens_q, cu_seqlens_k, seqused_q, seqused_k = ctx.saved_tensors
+        assert ctx.attention_chunk == 0, "FA3 backward does not support attention_chunk"
+        dq, dk, dv = torch.empty_like(q), torch.empty_like(k), torch.empty_like(v)
+        _flash_attn_backward(
+            dout,
+            q,
+            k,
+            v,
+            out,
+            softmax_lse,
+            cu_seqlens_q,
+            cu_seqlens_k,
+            seqused_q,
+            seqused_k,
+            ctx.max_seqlen_q,
+            ctx.max_seqlen_k,
+            dq,
+            dk,
+            dv,
+            ctx.softmax_scale,
+            ctx.causal,
+            ctx.window_size,
+            ctx.softcap,
+            ctx.deterministic,
+            ctx.sm_margin,
+        )
+        dq = dq[..., : q.shape[-1]]  # We could have padded the head dimension
+        dk = dk[..., : k.shape[-1]]
+        dv = dv[..., : v.shape[-1]]
+        return dq, dk, dv, None, None, None, None, None, None, None, None, None, None, None, None, None, None, None, None, None, None, None, None
+
+
+def flash_attn_qkvpacked_func(
+    qkv,
+    softmax_scale=None,
+    causal=False,
+    q_descale=None, k_descale=None, v_descale=None,
+    window_size=(-1, -1),
+    attention_chunk=0,
+    softcap=0.0,
+    deterministic=False,
+    num_heads_q=None,
+    sm_margin=0,
+):
+    """dropout_p should be set to 0.0 during evaluation
+    If Q, K, V are already stacked into 1 tensor, this function will be faster than
+    calling flash_attn_func on Q, K, V since the backward pass avoids explicit concatenation
+    of the gradients of Q, K, V.
+    For multi-query and grouped-query attention (MQA/GQA), please see
+    flash_attn_kvpacked_func and flash_attn_func.
+
+    If window_size != (-1, -1), implements sliding window local attention. Query at position i
+    will only attend to keys between [i - window_size[0], i + window_size[1]] inclusive.
+
+    Arguments:
+        qkv: (batch_size, seqlen, 3, nheads, headdim)
+        dropout_p: float. Dropout probability.
+        softmax_scale: float. The scaling of QK^T before applying softmax.
+            Default to 1 / sqrt(headdim).
+        causal: bool. Whether to apply causal attention mask (e.g., for auto-regressive modeling).
+        window_size: (left, right). If not (-1, -1), implements sliding window local attention.
+        softcap: float. Anything > 0 activates softcapping attention.
+        alibi_slopes: (nheads,) or (batch_size, nheads), fp32. A bias of (-alibi_slope * |i - j|) is added to
+            the attention score of query i and key j.
+        deterministic: bool. Whether to use the deterministic implementation of the backward pass,
+            which is slightly slower and uses more memory. The forward pass is always deterministic.
+        return_attn_probs: bool. Whether to return the attention probabilities. This option is for
+           testing only. The returned probabilities are not guaranteed to be correct
+           (they might not have the right scaling).
+    Return:
+        out: (batch_size, seqlen, nheads, headdim).
+        softmax_lse [optional, if return_attn_probs=True]: (batch_size, nheads, seqlen). The
+            logsumexp of each row of the matrix QK^T * scaling (e.g., log of the softmax
+            normalization factor).
+        S_dmask [optional, if return_attn_probs=True]: (batch_size, nheads, seqlen, seqlen).
+            The output of softmax (possibly with different scaling). It also encodes the dropout
+            pattern (negative means that location was dropped, nonnegative means it was kept).
+    """
+    return FlashAttnQKVPackedFunc.apply(
+        qkv,
+        softmax_scale,
+        causal,
+        q_descale, k_descale, v_descale,
+        window_size,
+        attention_chunk,
+        softcap,
+        deterministic,
+        num_heads_q,
+        sm_margin,
+    )
+
+
+def flash_attn_func(
+    q,
+    k,
+    v,
+    softmax_scale=None,
+    causal=False,
+    qv=None,
+    q_descale=None, k_descale=None, v_descale=None,
+    window_size=(-1, -1),
+    attention_chunk=0,
+    softcap=0.0,
+    num_splits=1,
+    pack_gqa=None,
+    deterministic=False,
+    sm_margin=0,
+):
+    """dropout_p should be set to 0.0 during evaluation
+    Supports multi-query and grouped-query attention (MQA/GQA) by passing in KV with fewer heads
+    than Q. Note that the number of heads in Q must be divisible by the number of heads in KV.
+    For example, if Q has 6 heads and K, V have 2 heads, head 0, 1, 2 of Q will attention to head
+    0 of K, V, and head 3, 4, 5 of Q will attention to head 1 of K, V.
+
+    If causal=True, the causal mask is aligned to the bottom right corner of the attention matrix.
+    For example, if seqlen_q = 2 and seqlen_k = 5, the causal mask (1 = keep, 0 = masked out) is:
+        1 1 1 1 0
+        1 1 1 1 1
+    If seqlen_q = 5 and seqlen_k = 2, the causal mask is:
+        0 0
+        0 0
+        0 0
+        1 0
+        1 1
+    If the row of the mask is all zero, the output will be zero.
+
+    If window_size != (-1, -1), implements sliding window local attention. Query at position i
+    will only attend to keys between
+    [i + seqlen_k - seqlen_q - window_size[0], i + seqlen_k - seqlen_q + window_size[1]] inclusive.
+
+    Arguments:
+        q: (batch_size, seqlen, nheads, headdim)
+        k: (batch_size, seqlen, nheads_k, headdim)
+        v: (batch_size, seqlen, nheads_k, headdim)
+        dropout_p: float. Dropout probability.
+        softmax_scale: float. The scaling of QK^T before applying softmax.
+            Default to 1 / sqrt(headdim).
+        causal: bool. Whether to apply causal attention mask (e.g., for auto-regressive modeling).
+        window_size: (left, right). If not (-1, -1), implements sliding window local attention.
+        alibi_slopes: (nheads,) or (batch_size, nheads), fp32. A bias of
+            (-alibi_slope * |i + seqlen_k - seqlen_q - j|)
+            is added to the attention score of query i and key j.
+        deterministic: bool. Whether to use the deterministic implementation of the backward pass,
+            which is slightly slower and uses more memory. The forward pass is always deterministic.
+        return_attn_probs: bool. Whether to return the attention probabilities. This option is for
+           testing only. The returned probabilities are not guaranteed to be correct
+           (they might not have the right scaling).
+    Return:
+        out: (batch_size, seqlen, nheads, headdim).
+        softmax_lse [optional, if return_attn_probs=True]: (batch_size, nheads, seqlen). The
+            logsumexp of each row of the matrix QK^T * scaling (e.g., log of the softmax
+            normalization factor).
+    """
+    return FlashAttnFunc.apply(
+        q,
+        k,
+        v,
+        softmax_scale,
+        causal,
+        qv,
+        q_descale, k_descale, v_descale,
+        window_size,
+        attention_chunk,
+        softcap,
+        num_splits,
+        pack_gqa,
+        deterministic,
+        sm_margin,
+    )
+
+
+def flash_attn_varlen_func(
+    q,
+    k,
+    v,
+    cu_seqlens_q,
+    cu_seqlens_k,
+    max_seqlen_q,
+    max_seqlen_k,
+    seqused_q=None,
+    seqused_k=None,
+    softmax_scale=None,
+    causal=False,
+    qv=None,
+    q_descale=None, k_descale=None, v_descale=None,
+    window_size=(-1, -1),
+    attention_chunk=0,
+    softcap=0.0,
+    num_splits=1,
+    pack_gqa=None,
+    deterministic=False,
+    sm_margin=0,
+):
+    return FlashAttnVarlenFunc.apply(
+        q,
+        k,
+        v,
+        cu_seqlens_q,
+        cu_seqlens_k,
+        seqused_q,
+        seqused_k,
+        max_seqlen_q,
+        max_seqlen_k,
+        softmax_scale,
+        causal,
+        qv,
+        q_descale, k_descale, v_descale,
+        window_size,
+        attention_chunk,
+        softcap,
+        num_splits,
+        pack_gqa,
+        deterministic,
+        sm_margin,
+    )
+
+
+def flash_attn_combine(out_partial, lse_partial, out=None, out_dtype=None):
+    return flash_attn_3_cuda.fwd_combine(out_partial, lse_partial, out, out_dtype)
+
+
+def flash_attn_with_kvcache(
+    q,
+    k_cache,
+    v_cache,
+    k=None,
+    v=None,
+    qv=None,
+    rotary_cos=None,
+    rotary_sin=None,
+    cache_seqlens: Optional[Union[(int, torch.Tensor)]] = None,
+    cache_batch_idx: Optional[torch.Tensor] = None,
+    cache_leftpad: Optional[torch.Tensor] = None,
+    page_table: Optional[torch.Tensor] = None,
+    cu_seqlens_q: Optional[torch.Tensor] = None,
+    cu_seqlens_k_new: Optional[torch.Tensor] = None,
+    max_seqlen_q: Optional[int] = None,
+    rotary_seqlens: Optional[torch.Tensor] = None,
+    q_descale: Optional[torch.Tensor] = None,
+    k_descale: Optional[torch.Tensor] = None,
+    v_descale: Optional[torch.Tensor] = None,
+    softmax_scale=None,
+    causal=False,
+    window_size=(-1, -1),  # -1 means infinite context window
+    attention_chunk=0,
+    softcap=0.0, # 0.0 means deactivated
+    rotary_interleaved=True,
+    scheduler_metadata=None,
+    num_splits=0,    # Can be tuned for speed
+    pack_gqa=None,   # Can be tuned for speed
+    sm_margin=0,     # Can be tuned if some SMs are used for communication
+    return_softmax_lse=False,
+):
+    """
+    If k and v are not None, k_cache and v_cache will be updated *inplace* with the new values from
+    k and v. This is useful for incremental decoding: you can pass in the cached keys/values from
+    the previous step, and update them with the new keys/values from the current step, and do
+    attention with the updated cache, all in 1 kernel.
+
+    If you pass in k / v, you must make sure that the cache is large enough to hold the new values.
+    For example, the KV cache could be pre-allocated with the max sequence length, and you can use
+    cache_seqlens to keep track of the current sequence lengths of each sequence in the batch.
+
+    Also apply rotary embedding if rotary_cos and rotary_sin are passed in. The key @k will be
+    rotated by rotary_cos and rotary_sin at indices cache_seqlens, cache_seqlens + 1, etc.
+    If causal or local (i.e., window_size != (-1, -1)), the query @q will be rotated by rotary_cos
+    and rotary_sin at indices cache_seqlens, cache_seqlens + 1, etc.
+    If not causal and not local, the query @q will be rotated by rotary_cos and rotary_sin at
+    indices cache_seqlens only (i.e. we consider all tokens in @q to be at position cache_seqlens).
+
+    See tests/test_flash_attn.py::test_flash_attn_kvcache for examples of how to use this function.
+
+    Supports multi-query and grouped-query attention (MQA/GQA) by passing in KV with fewer heads
+    than Q. Note that the number of heads in Q must be divisible by the number of heads in KV.
+    For example, if Q has 6 heads and K, V have 2 heads, head 0, 1, 2 of Q will attention to head
+    0 of K, V, and head 3, 4, 5 of Q will attention to head 1 of K, V.
+
+    If causal=True, the causal mask is aligned to the bottom right corner of the attention matrix.
+    For example, if seqlen_q = 2 and seqlen_k = 5, the causal mask (1 = keep, 0 = masked out) is:
+        1 1 1 1 0
+        1 1 1 1 1
+    If seqlen_q = 5 and seqlen_k = 2, the causal mask is:
+        0 0
+        0 0
+        0 0
+        1 0
+        1 1
+    If the row of the mask is all zero, the output will be zero.
+
+    If window_size != (-1, -1), implements sliding window local attention. Query at position i
+    will only attend to keys between
+    [i + seqlen_k - seqlen_q - window_size[0], i + seqlen_k - seqlen_q + window_size[1]] inclusive.
+
+    Note: Does not support backward pass.
+
+    Arguments:
+        q: (batch_size, seqlen, nheads, headdim)
+        k_cache: (batch_size_cache, seqlen_cache, nheads_k, headdim) if there's no page_table,
+            or (num_blocks, page_block_size, nheads_k, headdim) if there's a page_table (i.e. paged KV cache)
+            page_block_size must be a multiple of 256.
+        v_cache: (batch_size_cache, seqlen_cache, nheads_k, headdim_v) if there's no page_table,
+            or (num_blocks, page_block_size, nheads_k, headdim_v) if there's a page_table (i.e. paged KV cache)
+        k [optional]: (batch_size, seqlen_new, nheads_k, headdim). If not None, we concatenate
+            k with k_cache, starting at the indices specified by cache_seqlens.
+        v [optional]: (batch_size, seqlen_new, nheads_k, headdim_v). Similar to k.
+        qv [optional]: (batch_size, seqlen, nheads, headdim_v)
+        rotary_cos [optional]: (seqlen_ro, rotary_dim / 2). If not None, we apply rotary embedding
+            to k and q. Only applicable if k and v are passed in. rotary_dim must be divisible by 16.
+        rotary_sin [optional]: (seqlen_ro, rotary_dim / 2). Similar to rotary_cos.
+        cache_seqlens: int, or (batch_size,), dtype torch.int32. The sequence lengths of the
+            KV cache.
+        cache_batch_idx: (batch_size,), dtype torch.int32. The indices used to index into the KV cache.
+            If None, we assume that the batch indices are [0, 1, 2, ..., batch_size - 1].
+            If the indices are not distinct, and k and v are provided, the values updated in the cache
+                 might come from any of the duplicate indices.
+        cache_leftpad: (batch_size,), dtype torch.int32. The index that the KV cache starts. If None, assume 0.
+        page_table [optional]: (batch_size, max_num_blocks_per_seq), dtype torch.int32.
+        softmax_scale: float. The scaling of QK^T before applying softmax.
+            Default to 1 / sqrt(headdim).
+        causal: bool. Whether to apply causal attention mask (e.g., for auto-regressive modeling).
+        window_size: (left, right). If not (-1, -1), implements sliding window local attention.
+        softcap: float. Anything > 0 activates softcapping attention.
+        rotary_interleaved: bool. Only applicable if rotary_cos and rotary_sin are passed in.
+            If True, rotary embedding will combine dimensions 0 & 1, 2 & 3, etc. If False,
+            rotary embedding will combine dimensions 0 & rotary_dim / 2, 1 & rotary_dim / 2 + 1
+            (i.e. GPT-NeoX style).
+        num_splits: int. If > 1, split the key/value into this many chunks along the sequence.
+           If num_splits == 1, we don't split the key/value. If num_splits == 0, we use a heuristic
+           to automatically determine the number of splits.
+           Don't change this unless you know what you are doing.
+        return_softmax_lse: bool. Whether to return the logsumexp of the attention scores.
+
+    Return:
+        out: (batch_size, seqlen, nheads, headdim).
+        softmax_lse [optional, if return_softmax_lse=True]: (batch_size, nheads, seqlen). The
+            logsumexp of each row of the matrix QK^T * scaling (e.g., log of the softmax
+            normalization factor).
+    """
+    assert k_cache.stride(-1) == 1, "k_cache must have contiguous last dimension"
+    assert v_cache.stride(-1) == 1, "v_cache must have contiguous last dimension"
+    if softmax_scale is None:
+        softmax_scale = (q.shape[-1] + (qv.shape[-1] if qv is not None else 0)) ** (-0.5)
+    if cache_seqlens is not None and isinstance(cache_seqlens, int):
+        cache_seqlens = torch.full(
+            (k_cache.shape[0],), cache_seqlens, dtype=torch.int32, device=k_cache.device
+        )
+        cache_seqlens = maybe_contiguous(cache_seqlens)
+    out, softmax_lse, *rest = _flash_attn_forward(
+        q,
+        k_cache,
+        v_cache,
+        k,
+        v,
+        qv,
+        None,  # out
+        cu_seqlens_q,
+        None,  # cu_seqlens_k
+        cu_seqlens_k_new,
+        None,  # seqused_q
+        cache_seqlens,
+        max_seqlen_q,
+        None,  # max_seqlen_k
+        page_table,
+        cache_batch_idx,
+        cache_leftpad,
+        rotary_cos,
+        rotary_sin,
+        rotary_seqlens,
+        q_descale, k_descale, v_descale,
+        softmax_scale,
+        causal=causal,
+        window_size=window_size,
+        attention_chunk=attention_chunk,
+        softcap=softcap,
+        rotary_interleaved=rotary_interleaved,
+        scheduler_metadata=scheduler_metadata,
+        num_splits=num_splits,
+        pack_gqa=pack_gqa,
+        sm_margin=sm_margin,
+    )
+    # return (out, softmax_lse) if return_softmax_lse else out
+    return (out, softmax_lse, *rest) if return_softmax_lse else out
+
+
+def get_scheduler_metadata(
+    batch_size, max_seqlen_q, max_seqlen_k, num_heads_q, num_heads_kv, headdim,
+    cache_seqlens: torch.Tensor,
+    qkv_dtype=torch.bfloat16,
+    headdim_v=None,
+    cu_seqlens_q: Optional[torch.Tensor] = None,
+    cu_seqlens_k_new: Optional[torch.Tensor] = None,
+    cache_leftpad: Optional[torch.Tensor] = None,
+    page_size: Optional[int] = None,
+    max_seqlen_k_new=0,
+    causal=False,
+    window_size=(-1, -1),  # -1 means infinite context window
+    attention_chunk=0,
+    has_softcap=False,
+    num_splits=0,    # Can be tuned for speed
+    pack_gqa=None,   # Can be tuned for speed
+    sm_margin=0,     # Can be tuned if some SMs are used for communication
+):
+    cache_seqlens = maybe_contiguous(cache_seqlens)
+    if headdim_v is None:
+        headdim_v = headdim
+    scheduler_metadata = flash_attn_3_cuda.get_scheduler_metadata(
+        batch_size, max_seqlen_q, max_seqlen_k, num_heads_q, num_heads_kv, headdim, headdim_v,
+        qkv_dtype,
+        cache_seqlens,
+        cu_seqlens_q,
+        None,  # cu_seqlens_k
+        cu_seqlens_k_new,
+        None,  # seqused_q
+        cache_leftpad,
+        page_size,
+        max_seqlen_k_new,
+        causal,
+        window_size[0], window_size[1],
+        attention_chunk,
+        has_softcap,
+        num_splits,
+        pack_gqa,
+        sm_margin,
+    )
+    return scheduler_metadata