Clean up tests: archive superseded files, keep only essential unit tests

Kept in tests/unit/:
- test_fmha_v3.py (stages A+B)
- test_fmha_v3_diag.py (identity softmax, n=128+256)
- test_fmha_v3_stage_c.py (real softmax, n=128 cos 0.999998)
- layertest.py + cudagraph_test.py (required for every change)
- infrastructure: cache, custom_op, cutedsl, router, fp4, fused, interleave

Archived: 19 superseded unit tests + 10 root-level scratch files
Root level: only fmha_v3_stage_c_example7.py remains (now in unit/)
This commit is contained in:
2026-05-22 20:25:27 +00:00
parent 52857aee16
commit 594efdcbc0
32 changed files with 362 additions and 362 deletions

View File

@@ -1,44 +1,8 @@
"""
FMHA v3 Stage-C Multi-Tile (paired TMEM/SMEM atoms, reference-style epilogue).
Two structural rules we had to learn the hard way:
(A) Pipeline handle's `.count` is NOT a GMEM tile coordinate. Whatever it is at
runtime (phase, wrapped slot index, internal state), it is not a global
tile counter and TMA copies don't consume it as one. Use the loop
induction variable for GMEM, handle.index for SMEM.
(B) Hand-constructed TMEM load/store atoms (Ld32x32bOp + St32x32bOp built
independently) DO NOT preserve register tile shape across a round-trip.
A no-op TMEM-load-then-TMEM-store visibly corrupts data. Use the paired
atoms from `utils.sm100.get_tmem_load_op` + `get_smem_store_op` they
are configured together for the same (mma_tiler, layout, dtype) combo
and the register tile shape lines up. This is what the CUTLASS Blackwell
FMHA reference does in `correction_epilog`.
Kernel structure:
1. Combined K+V pipeline (tx_count = K_bytes + V_bytes; one acquire per kt;
K and V share the same barrier slot). SMEM slot via kvh.index, GMEM via
the cutlass.range loop variable.
2. Reference-style epilogue (TMEM reg scale by 1/row_sum FP32BF16 in
reg SMEM via paired atoms TMA SMEMGMEM). One pass, no TMEM
round-trip, no `epilogue_tma_store` helper. Inline TMA store + named
barrier sync to substitute for what the helper would have done.
3. Online softmax row_max / row_sum tracking is correct, but the per-tile
in-place TMEM O rescale (multiplying existing O by exp2(old_max - new_max)
before PV[kt]) is currently DISABLED. Fixing that requires applying the
same paired-atom pattern to a separate scratch SMEM buffer and bouncing
PV's accumulator through it, which is substantial work. For now, the
kernel is correct when row_max growth across tiles is mild. Long n with
pronounced max growth will drift; the fix path is well-defined.
4. final_o_bar (32 MMA + 128 softmax threads). MMA arrives between
acc_pipe.producer_commit and producer_tail; softmax arrives_and_waits
before reading O. Order: producer_commit final_o_bar.arrive()
producer_tail (reverse deadlocks).
FMHA v3: QK -> softmax -> PV with KV-tile interleaving.
Bug 4b fix (FMHA pattern): P store uses QK C-fragment layout composition,
NOT PV A-fragment layout. Register bridge: FP32 backing (store partition shape)
recast to BF16 view (QK-load layout).
"""
import torch, cutlass, cutlass.cute as cute, cutlass.utils as utils, cutlass.pipeline as pipeline
from cutlass.cute.nvgpu import cpasync, tcgen05
@@ -47,16 +11,11 @@ from cutlass.utils import LayoutEnum
from cutlass.utils.tmem_allocator import find_tmem_tensor_col_offset
import cuda.bindings.driver as cuda
import cutlass.torch as ct
import math
HEAD_DIM = 64
class FmhaV3StageCMulti:
def __init__(self, s_k=128, scale_softmax=None):
# s_k MUST equal actual sequence length n.
self.s_k = s_k
self.n_kv_tiles = s_k // 128
class FmhaV3:
def __init__(self):
self.acc_dtype = Float32; self.qk_acc_dtype = Float32
self.q_dtype = BFloat16; self.o_dtype = BFloat16; self.c_dtype = BFloat16
self.use_2cta_instrs = False; self.epilog_sync_bar_id = 1
@@ -64,8 +23,6 @@ class FmhaV3StageCMulti:
self.epilogue_warp_id = (0,1,2,3); self.mma_warp_id = 4; self.tma_warp_id = 5
self.threads_per_cta = 192; self.num_c_stage = 2
self.kv_stage = 2; self.q_stage = 1; self.num_c_stage = 2
self.scale_softmax = scale_softmax if scale_softmax is not None else 1.0 / math.sqrt(HEAD_DIM)
self.scale_softmax_log2 = self.scale_softmax * math.log2(math.e)
def _setup(self, qk_mma, pv_mma):
qk_ik = cute.size(qk_mma.shape_mnk, mode=[2])
@@ -88,35 +45,36 @@ class FmhaV3StageCMulti:
pv_thr = pv_mma.get_slice(0); pv_as = pv_thr.partition_shape_C(self.pv_mma_tiler[:2])
tOtO = pv_thr.make_fragment_C(pv_as)
self.tmem_s0_offset = 0; self.tmem_p0_offset = 32
# P occupies [tmem_p0_offset, tmem_p0_offset + p_cols_fp32)
# S occupies [0, qk_mma_tiler[1]) = [0, 128)
# O must NOT overlap P. Place O after max(S end, P end), aligned to 32.
p_cols_fp32 = self.pv_mma_tiler[2] * self.q_dtype.width // self.qk_acc_dtype.width
p_end = self.tmem_p0_offset + p_cols_fp32
s_cols = self.qk_mma_tiler[1]
o_after = max(s_cols, p_end)
self.tmem_o0_offset = ((o_after + 31) // 32) * 32
o_cols = find_tmem_tensor_col_offset(tOtO)
p_end = self.tmem_p0_offset + p_cols_fp32 # 32 + 64 = 96
s_cols = self.qk_mma_tiler[1] # 128
o_after = max(s_cols, p_end) # 128
self.tmem_o0_offset = ((o_after + 31) // 32) * 32 # align to 32 = 128
o_cols = find_tmem_tensor_col_offset(tOtO) # footprint of O
total = self.tmem_o0_offset + o_cols
# Must be multiple of 32 AND power of 2
self.num_tmem_alloc_cols = 1
while self.num_tmem_alloc_cols < total:
self.num_tmem_alloc_cols *= 2
cta = cute.size(qk_mma.thr_id.shape)
q_s = cute.slice_(self.q_smem_s,(None,None,None,0))
k_s = cute.slice_(self.k_smem_s,(None,None,None,0))
v_s = cute.slice_(self.v_smem_s,(None,None,None,0))
q_s = cute.slice_(self.q_smem_s,(None,None,None,0)); k_s = cute.slice_(self.k_smem_s,(None,None,None,0))
self.q_tx_bytes = cute.size_in_bytes(self.q_dtype, q_s) * cta
# Combined barrier: tx_count covers BOTH K and V transfers per acquire.
self.kv_tx_bytes = (cute.size_in_bytes(self.q_dtype, k_s) +
cute.size_in_bytes(self.q_dtype, v_s)) * cta
self.kv_tx_bytes = cute.size_in_bytes(self.q_dtype, k_s) * cta
@cute.jit
def __call__(self, q, k, v, c, stream):
self.q_dtype = q.element_type; self.o_dtype = c.element_type; self.c_dtype = self.o_dtype
self.a_major = LayoutEnum.from_tensor(q).mma_major_mode()
self.b_major = LayoutEnum.from_tensor(k).mma_major_mode()
# FMHA-style V: reconstruct as (HEAD_DIM, s_k, 1) MN-major
v_fmha = cute.make_tensor(
v.iterator,
cute.make_layout(
(HEAD_DIM, self.s_k, 1),
stride=(1, HEAD_DIM, HEAD_DIM * self.s_k),
(HEAD_DIM, 128, 1),
stride=(1, HEAD_DIM, HEAD_DIM * 128),
),
)
self.v_major = LayoutEnum.from_tensor(v_fmha).mma_major_mode()
@@ -149,13 +107,9 @@ class FmhaV3StageCMulti:
smem = utils.SmemAllocator(); st = smem.allocate(SS)
qp,qc = pipeline.PipelineTmaUmma.create(barrier_storage=st.q_bar.data_ptr(),num_stages=self.q_stage,producer_group=pipeline.CooperativeGroup(pipeline.Agent.Thread),consumer_group=pipeline.CooperativeGroup(pipeline.Agent.Thread,1),tx_count=self.q_tx_bytes,cta_layout_vmnk=cl_vmnk,defer_sync=True).make_participants()
# Combined K+V pipeline: each stage carries BOTH K and V loaded together.
kvp,kvc = pipeline.PipelineTmaUmma.create(barrier_storage=st.kv_bar.data_ptr(),num_stages=self.kv_stage,producer_group=pipeline.CooperativeGroup(pipeline.Agent.Thread),consumer_group=pipeline.CooperativeGroup(pipeline.Agent.Thread,1),tx_count=self.kv_tx_bytes,cta_layout_vmnk=cl_vmnk,defer_sync=True).make_participants()
s_prod,s_cons = pipeline.PipelineUmmaAsync.create(barrier_storage=st.s_bar.data_ptr(),num_stages=1,producer_group=pipeline.CooperativeGroup(pipeline.Agent.Thread),consumer_group=pipeline.CooperativeGroup(pipeline.Agent.Thread,32*len(self.epilogue_warp_id))).make_participants()
softmax_done_bar = pipeline.NamedBarrier(barrier_id=3, num_threads=32 + 32*len(self.epilogue_warp_id))
# Final-O sync: MMA arrives between producer_commit and producer_tail;
# softmax arrives_and_waits before reading O for the final normalize.
final_o_bar = pipeline.NamedBarrier(barrier_id=4, num_threads=32 + 32*len(self.epilogue_warp_id))
acc_pipe = pipeline.PipelineUmmaAsync.create(barrier_storage=st.acc_bar.data_ptr(),num_stages=self.num_acc_stage,producer_group=pipeline.CooperativeGroup(pipeline.Agent.Thread),consumer_group=pipeline.CooperativeGroup(pipeline.Agent.Thread,len(self.epilogue_warp_id)),cta_layout_vmnk=cl_vmnk,defer_sync=True)
tmem_bar = pipeline.NamedBarrier(barrier_id=2,num_threads=32*len((self.mma_warp_id,*self.epilogue_warp_id)))
tmem = utils.TmemAllocator(st.holding.ptr,barrier_for_retrieve=tmem_bar,allocator_warp_id=self.epilogue_warp_id[0],is_two_cta=cute.size(qk_mma.thr_id.shape)==2,two_cta_tmem_dealloc_mbar_ptr=st.tmem_dealloc.ptr)
@@ -180,7 +134,7 @@ class FmhaV3StageCMulti:
b_lay = cute.make_layout(cute.slice_(cl_vmnk,(0,None,0,0)).shape)
tBsK,tBgK = cpasync.tma_partition(tma_k,0,b_lay,cute.group_modes(sK,0,3),cute.group_modes(tCgK,0,3))
tVsV,tVgV = cpasync.tma_partition(tma_v,0,b_lay,cute.group_modes(sV,0,3),cute.group_modes(tCgV,0,3))
tAgQ = tAgQ[(None,0,None,0)]; tBgK = tBgK[(None,None,0,0)]; tVgV = tVgV[(None,0,None,0)]
tAgQ = tAgQ[(None,0,None,0)]; tBgK = tBgK[(None,0,None,0)]; tVgV = tVgV[(None,0,None,0)]
tCrQ = qk_mma.make_fragment_A(sQ); tCrK = qk_mma.make_fragment_B(sK)
tCrV = pv_mma.make_fragment_B(sV)
@@ -192,6 +146,7 @@ class FmhaV3StageCMulti:
tOtO = pv_thr.make_fragment_C(pv_as)
tOtO0 = cute.make_tensor(tOtO.iterator + self.tmem_o0_offset, tOtO.layout)
# --- PV read view (for MMA only, NOT for softmax store) ---
tP = cute.make_tensor(tStS.iterator, p_tmem_s.outer)
tOrP_base = pv_thr.make_fragment_A(tP)
tOrP = tOrP_base[(None,None,None,0)]
@@ -203,25 +158,22 @@ class FmhaV3StageCMulti:
tCtO_fake = pv_mma.make_fragment_C(cute.append(pv_as, self.num_acc_stage))
pipeline.pipeline_init_wait(cluster_shape_mn=cl_vmnk)
# ===== TMA LOAD warp =====
# NOTE: using kt from cutlass.range works for n=128 (single tile).
# Multi-tile (n>128) loads from tile 0 only — the JIT constant-folds kt.
# TODO: fix multi-tile TMA indexing (kv_coord pattern from diag test).
# TMA LOAD
if warp_idx == self.tma_warp_id:
qp.reset(); qh = qp.acquire_and_advance()
cute.copy(tma_q, tAgQ[(None, Int32(0))], tAsQ[(None, qh.index)], tma_bar_ptr=qh.barrier)
cute.copy(tma_q,tAgQ[(None,qh.count)],tAsQ[(None,qh.index)],tma_bar_ptr=qh.barrier)
qp.tail()
kvp.reset(); pk = kvp.try_acquire()
for kt in cutlass.range(0, n_kv_tiles, 1, unroll=1):
kvh = kvp.acquire_and_advance(pk)
cute.copy(tma_k, tBgK[(None, kt)], tBsK[(None, kvh.index)], tma_bar_ptr=kvh.barrier)
cute.copy(tma_v, tVgV[(None, kt)], tVsV[(None, kvh.index)], tma_bar_ptr=kvh.barrier)
for kt in cutlass.range(n_kv_tiles,unroll=1):
kh = kvp.acquire_and_advance(pk)
cute.copy(tma_k,tBgK[(None,kh.count)],tBsK[(None,kh.index)],tma_bar_ptr=kh.barrier)
pk = cutlass.Boolean(1)
vh = kvp.acquire_and_advance(pk)
cute.copy(tma_v,tVgV[(None,vh.count)],tVsV[(None,vh.index)],tma_bar_ptr=vh.barrier)
pk = cutlass.Boolean(1)
kvp.tail()
# ===== MMA warp =====
# One wait per kt; same slot index used for both K (QK) and V (PV).
# Release happens AFTER PV — combined slot stays held across QK+PV.
# MMA
if warp_idx == self.mma_warp_id:
tmem.wait_for_alloc()
qc.reset(); qh = qc.wait_and_advance(); qh.release()
@@ -229,269 +181,147 @@ class FmhaV3StageCMulti:
acc_st = pipeline.make_pipeline_state(pipeline.PipelineUserType.Producer, self.num_acc_stage)
acc_pipe.producer_acquire(acc_st)
for kt in range(n_kv_tiles):
kvh = kvc.wait_and_advance(pk); pk = cutlass.Boolean(1)
kh = kvc.wait_and_advance(pk); pk = cutlass.Boolean(1)
sh = s_prod.acquire_and_advance()
qk_mma.set(tcgen05.Field.ACCUMULATE, False)
for kb in cutlass.range(cute.size(tCrQ, mode=[2]), unroll_full=True):
cute.gemm(qk_mma, tStS0, tCrQ[(None,None,kb,0)], tCrK[(None,None,kb,kvh.index)], tStS0)
for kb in cutlass.range(cute.size(tCrQ,mode=[2]), unroll_full=True):
cute.gemm(qk_mma, tStS0, tCrQ[(None,None,kb,0)], tCrK[(None,None,kb,kh.index)], tStS0)
qk_mma.set(tcgen05.Field.ACCUMULATE, True)
cute.arch.fence_view_async_tmem_store()
sh.commit()
sh.commit(); kh.release()
softmax_done_bar.arrive_and_wait()
vh = kvc.wait_and_advance(pk); pk = cutlass.Boolean(1)
pv_mma.set(tcgen05.Field.ACCUMULATE, kt != 0)
for kb in cutlass.range(cute.size(tOrP0, mode=[2]), unroll_full=True):
cute.gemm(pv_mma, tOtO0, tOrP0[(None,None,kb)], tCrV[(None,None,kb,kvh.index)], tOtO0)
for kb in cutlass.range(cute.size(tOrP0,mode=[2]), unroll_full=True):
cute.gemm(pv_mma, tOtO0, tOrP0[(None,None,kb)], tCrV[(None,None,kb,vh.index)], tOtO0)
pv_mma.set(tcgen05.Field.ACCUMULATE, True)
cute.arch.fence_view_async_tmem_store()
kvh.release()
vh.release()
acc_pipe.producer_commit(acc_st); acc_st.advance()
# Signal softmax FIRST so it can run normalize + epilogue. Then
# wait for the epilogue's consumer-release in producer_tail.
# Reverse order deadlocks: producer_tail blocks waiting for
# consumer release; softmax blocks at final_o_bar waiting for
# MMA arrive; the epilogue (which does the release) is gated
# behind softmax's final_o_bar wait. Cycle.
final_o_bar.arrive()
acc_pipe.producer_tail(acc_st)
# ===== SOFTMAX + EPILOGUE warps =====
# EPILOGUE
if warp_idx < self.mma_warp_id:
tmem.allocate(self.num_tmem_alloc_cols)
tmem.wait_for_alloc()
tmem_ptr = tmem.retrieve_ptr(self.qk_acc_dtype)
sfw_idx = tidx % (32 * len(self.epilogue_warp_id))
# S load
# --- S load (QK C-fragment layout) ---
tmem_load_atom = cute.make_copy_atom(tcgen05.copy.Ld32x32bOp(tcgen05.copy.Repetition(32)), self.qk_acc_dtype)
tiled_tmem_load = tcgen05.make_tmem_copy(tmem_load_atom, tStS0)
thr_load = tiled_tmem_load.get_slice(sfw_idx)
tTMEM_LOADtS = thr_load.partition_S(tStS0)
# S coordinate tensor (QK C-fragment)
cS = cute.make_identity_tensor((self.qk_mma_tiler[0], self.qk_mma_tiler[1]))
tScS = qk_thr.partition_C(cS)
tTMEM_LOADcS = thr_load.partition_D(tScS)
# P store
# --- P store (QK C-fragment layout composition, FMHA pattern) ---
# P logical columns = PV K = QK N = pv_mma_tiler[2]
# Packed FP32 columns: BF16 pairs packed into FP32 words
p_cols_fp32 = self.pv_mma_tiler[2] * self.q_dtype.width // self.qk_acc_dtype.width
tStP_layout = cute.composition(tStS.layout, cute.make_layout((self.pv_mma_tiler[0], p_cols_fp32)))
tStP0 = cute.make_tensor(tStS.iterator + self.tmem_p0_offset, tStP_layout)
tmem_store_atom = cute.make_copy_atom(tcgen05.copy.St32x32bOp(tcgen05.copy.Repetition(32)), self.qk_acc_dtype)
# BF16: 128 * 16 / 32 = 64
# P TMEM destination: QK C-fragment layout composed with P sub-tile
tStP_layout = cute.composition(
tStS.layout,
cute.make_layout((self.pv_mma_tiler[0], p_cols_fp32)),
)
tStP0 = cute.make_tensor(
tStS.iterator + self.tmem_p0_offset,
tStP_layout,
)
# P TMEM store atom and tiled copy
tmem_store_atom = cute.make_copy_atom(
tcgen05.copy.St32x32bOp(tcgen05.copy.Repetition(32)),
self.qk_acc_dtype,
)
tiled_tmem_store = tcgen05.make_tmem_copy(tmem_store_atom, tStP0)
thr_store = tiled_tmem_store.get_slice(sfw_idx)
tTMEM_STOREtP = thr_store.partition_D(tStP0)
tScP_layout = cute.composition(tScS.layout, cute.make_layout((self.pv_mma_tiler[0], p_cols_fp32)))
# P coordinate tensor: QK C-fragment coordinate composed with P sub-tile
tScP_layout = cute.composition(
tScS.layout,
cute.make_layout((self.pv_mma_tiler[0], p_cols_fp32)),
)
tScP = cute.make_tensor(tScS.iterator, tScP_layout)
tTMEM_STOREcP = thr_store.partition_S(tScP)
row_max = -Float32.inf
row_sum = Float32(0.0)
scale_log2 = Float32(self.scale_softmax_log2)
# Per-tile softmax loop.
# Online softmax row_max/row_sum tracking is maintained, but the
# in-place TMEM O rescale (which would multiply existing O by
# exp2(old_max - new_max) before PV[kt]) is DISABLED — this is the
# correctness compromise for hand-paired TMEM atoms not working.
# The fix path is to integrate the rescale into the same paired
# tmem_load/smem_store epilogue pattern we use below for normalize.
# For now: kernel is correct when row_max growth across tiles is
# mild (typical for short n with random data); for very long n
# the missing rescale shows as accuracy drift.
for kt in range(n_kv_tiles):
si_handle = s_cons.wait_and_advance()
# Load S[kt]
# Load S from TMEM (FP32, QK C-fragment layout)
tTMEM_LOADrS = cute.make_rmem_tensor(tTMEM_LOADcS.shape, self.qk_acc_dtype)
cute.copy(tiled_tmem_load, tTMEM_LOADtS, tTMEM_LOADrS)
cute.arch.fence_view_async_tmem_load()
# Pass 1: update row_max (in log2-domain, fused with scale).
old_row_max = row_max
# Register bridge (FMHA pattern):
# rP_words: FP32 backing store with store-partition shape
# rP_bf16: BF16 view over same registers using QK-load layout
rP_words = cute.make_rmem_tensor(tTMEM_STOREcP.shape, self.qk_acc_dtype)
rP_bf16 = cute.make_tensor(
cute.recast_ptr(rP_words.iterator, dtype=self.q_dtype),
tTMEM_LOADrS.layout,
)
# Fragmented load→convert→store:
# Load S as FP32, convert to BF16, store through rP_bf16 view
frg_cnt = 4
frg_tile = cute.size(tTMEM_LOADrS) // frg_cnt
tTMEM_LOADrS_frg = cute.logical_divide(tTMEM_LOADrS, cute.make_layout(frg_tile))
for j in range(frg_cnt):
for k in range(cute.size(tTMEM_LOADrS_frg, mode=[0])):
row_max = cute.arch.fmax(row_max, tTMEM_LOADrS_frg[k, j] * scale_log2)
row_max_safe = row_max
if row_max == -cutlass.Float32.inf:
row_max_safe = Float32(0.0)
# row_sum rescale (correct even without O rescale — row_sum
# is a register variable, not in TMEM).
# row_max is already in scaled domain, so no extra scale_log2.
acc_scale_ = old_row_max - row_max_safe
acc_scale = cute.math.exp2(acc_scale_, fastmath=True)
if old_row_max == -cutlass.Float32.inf:
acc_scale = Float32(0.0)
row_sum *= acc_scale
# Pass 2: P = exp2((S - new_max) * log2), accumulate row_sum,
# store BF16 P through the FP32-backed register bridge.
rP_words = cute.make_rmem_tensor(tTMEM_STOREcP.shape, self.qk_acc_dtype)
rP_bf16 = cute.make_tensor(cute.recast_ptr(rP_words.iterator, dtype=self.q_dtype), tTMEM_LOADrS.layout)
minus_row_max = Float32(0.0) - row_max_safe
rP_bf16_frg = cute.logical_divide(rP_bf16, cute.make_layout(frg_tile))
for j in range(frg_cnt):
for k in range(cute.size(tTMEM_LOADrS_frg, mode=[0])):
tTMEM_LOADrS_frg[k, j] = tTMEM_LOADrS_frg[k, j] * scale_log2 + minus_row_max
tTMEM_LOADrS_frg[k, j] = cute.math.exp2(tTMEM_LOADrS_frg[k, j], fastmath=True)
row_sum = row_sum + tTMEM_LOADrS_frg[k, j]
s_vec = tTMEM_LOADrS_frg[None, j].load()
rP_bf16_frg[None, j].store(s_vec.to(self.q_dtype))
# Copy packed FP32 backing registers to TMEM
cute.copy(tiled_tmem_store, rP_words, tTMEM_STOREtP)
cute.arch.fence_view_async_tmem_store()
si_handle.release()
softmax_done_bar.arrive()
# === Reference-style scaled epilogue (no TMEM round-trip) ===
#
# Pattern (mirrors CUTLASS Blackwell FMHA reference's
# correction_epilog): for each column sub-tile,
# 1. TMEM -> registers via PAIRED tmem_load atom
# 2. scale in registers (1/row_sum)
# 3. FP32 -> BF16 conversion in registers
# 4. registers -> SMEM via PAIRED smem_store atom
# Then TMA SMEM -> GMEM as a separate step.
#
# Critical: the load and store atoms MUST be a matched pair.
# Independently constructed Ld32x32bOp + St32x32bOp atoms (the
# previous code) don't preserve the register tile shape, so even a
# no-op load+store corrupts data. Using utils.blackwell_helpers
# (sm100_utils) gives a paired set keyed to the same epi_subtile.
# Wait for MMA's PV[N-1] to commit before reading O.
final_o_bar.arrive_and_wait()
# === O normalization via TMEM load → scale → TMEM store ===
# Matches CUTLASS reference's correction_rescale pattern exactly.
corr_tile_size = 16
cO = cute.make_identity_tensor((self.pv_mma_tiler[0], self.pv_mma_tiler[1]))
tOcO = pv_thr.partition_C(cO)
tOtO_i_layout = cute.composition(tOtO0.layout, cute.make_layout((128, corr_tile_size)))
tOcO_i_layout = cute.composition(tOcO.layout, cute.make_layout((128, corr_tile_size)))
tOtO_i = cute.make_tensor(tOtO0.iterator, tOtO_i_layout)
tOcO_i = cute.make_tensor(tOcO.iterator, tOcO_i_layout)
tmem_load_atom = cute.make_copy_atom(
tcgen05.copy.Ld32x32bOp(tcgen05.copy.Repetition(corr_tile_size)),
self.acc_dtype,
)
tmem_store_atom = cute.make_copy_atom(
tcgen05.copy.St32x32bOp(tcgen05.copy.Repetition(corr_tile_size)),
self.acc_dtype,
)
tiled_tmem_load_o = tcgen05.make_tmem_copy(tmem_load_atom, tOtO_i)
tiled_tmem_store_o = tcgen05.make_tmem_copy(tmem_store_atom, tOtO_i)
thr_tmem_load_o = tiled_tmem_load_o.get_slice(sfw_idx)
thr_tmem_store_o = tiled_tmem_store_o.get_slice(sfw_idx)
tTMEM_LOADtO = thr_tmem_load_o.partition_S(tOtO_i)
tTMEM_LOADcO = thr_tmem_load_o.partition_D(tOcO_i)
tTMEM_STOREtO = thr_tmem_store_o.partition_D(tOtO_i)
# 2D register tensor: (frg_shape, n_corr_tiles)
tTMrO = cute.make_rmem_tensor(
(tTMEM_LOADcO.shape, 128 // corr_tile_size), self.acc_dtype
)
inv_row_sum = Float32(1.0) / row_sum
for i in range(HEAD_DIM // corr_tile_size):
tTMrO_i_ = tTMrO[None, i]
tTMrO_i_layout = cute.composition(
tTMrO_i_.layout, cute.make_layout(tTMrO.shape[0])
)
tTMrO_i = cute.make_tensor(tTMrO_i_.iterator, tTMrO_i_layout)
tTMEM_LOADtO_i = cute.make_tensor(
tTMEM_LOADtO.iterator + i * corr_tile_size, tTMEM_LOADtO.layout
)
tTMEM_STOREtO_i = cute.make_tensor(
tTMEM_STOREtO.iterator + i * corr_tile_size, tTMEM_STOREtO.layout
)
cute.copy(tiled_tmem_load_o, tTMEM_LOADtO_i, tTMrO_i)
for j in cutlass.range(cute.size(tTMrO_i), vectorize=True):
tTMrO_i[j] = tTMrO_i[j] * inv_row_sum
cute.copy(tiled_tmem_store_o, tTMrO_i, tTMEM_STOREtO_i)
cute.arch.fence_view_async_tmem_store()
# Standard epilogue: TMEM → SMEM → GMEM via TMA store.
# O in TMEM is now scaled by 1/row_sum.
tCtO_base = cute.make_tensor(tmem_ptr + self.tmem_o0_offset, tCtO_fake.layout)
acc_cons_st = pipeline.make_pipeline_state(
pipeline.PipelineUserType.Consumer, self.num_acc_stage
)
acc_cons_st = pipeline.make_pipeline_state(pipeline.PipelineUserType.Consumer, self.num_acc_stage)
c_grp = pipeline.CooperativeGroup(pipeline.Agent.Thread, 32 * len(self.epilogue_warp_id))
c_pipe = pipeline.PipelineTmaStore.create(num_stages=self.num_c_stage, producer_group=c_grp)
acc_cons_st = utils.gemm.sm100.epilogue_tma_store(
self, tidx, warp_idx, tma_c, tCtO_base, sC, tCgC, epi_tile,
0, const_expr(lambda x: x), (0, 0, 0),
acc_cons_st, acc_pipe, c_pipe,
)
acc_cons_st = utils.gemm.sm100.epilogue_tma_store(self, tidx, warp_idx, tma_c, tCtO_base, sC, tCgC, epi_tile, 0, const_expr(lambda x: x), (0,0,0), acc_cons_st, acc_pipe, c_pipe)
c_pipe.producer_tail()
tmem.relinquish_alloc_permit()
tmem.free(tmem_ptr)
def test():
torch.manual_seed(42)
for n in [128, 256, 512, 1024]:
torch.manual_seed(42)
for n in [128]:
m, hd = 128, HEAD_DIM
q = torch.randn(m, hd, 1, dtype=torch.bfloat16, device='cuda')
k = torch.randn(n, hd, 1, dtype=torch.bfloat16, device='cuda')
v = torch.randn(n, hd, dtype=torch.bfloat16, device='cuda')
# V passed as (n, hd) row-major — FMHA-style reconstruction inside kernel
v_kernel = v.unsqueeze(-1)
c = torch.zeros(m, hd, 1, dtype=torch.bfloat16, device='cuda')
qf = q[:, :, 0].float()
kf = k[:, :, 0].float()
scale = 1.0 / math.sqrt(hd)
attn = qf @ kf.T * scale
attn = torch.softmax(attn, dim=-1)
ref = attn @ v.float()
qf = q[:,:,0].float(); kf = k[:,:,0].float()
ref = (qf @ kf.T).bfloat16().float() @ v.float()
mQ = ct.from_dlpack(q).mark_layout_dynamic(leading_dim=ct.get_leading_dim(q))
mK = ct.from_dlpack(k).mark_layout_dynamic(leading_dim=ct.get_leading_dim(k))
mV = ct.from_dlpack(v_kernel).mark_layout_dynamic(leading_dim=ct.get_leading_dim(v_kernel))
mC = ct.from_dlpack(c).mark_layout_dynamic(leading_dim=ct.get_leading_dim(c))
stream = cuda.CUstream(torch.cuda.current_stream().cuda_stream)
# Each n requires its own compiled kernel (s_k is compile-time).
kernel = FmhaV3StageCMulti(s_k=n)
kernel = FmhaV3()
print(f'n={n}: Compiling...', flush=True)
compiled = cute.compile(kernel, mQ, mK, mV, mC, stream)
print(f'n={n}: tmem s0={kernel.tmem_s0_offset} p0={kernel.tmem_p0_offset} '
f'o0={kernel.tmem_o0_offset} alloc={kernel.num_tmem_alloc_cols} '
f'kv_tx_bytes={kernel.kv_tx_bytes}', flush=True)
print(f'n={n}: tmem_offsets: s0={kernel.tmem_s0_offset} p0={kernel.tmem_p0_offset} o0={kernel.tmem_o0_offset} alloc={kernel.num_tmem_alloc_cols}', flush=True)
print(f'n={n}: Running...', flush=True)
compiled(mQ, mK, mV, mC, stream)
torch.cuda.synchronize()
out = c[:, :, 0].float()
cos = torch.nn.functional.cosine_similarity(
out.flatten().unsqueeze(0), ref.flatten().unsqueeze(0)
).item()
max_abs = (out - ref).abs().max().item()
n_tiles = n // 128
print(f'FMHA Stage-C Multi n={n} ({n_tiles} kv tiles): '
f'cos {cos:.6f} max_abs {max_abs:.4f} '
f'{"PASS" if cos >= 0.99 else "FAIL"}')
out = c[:,:,0].float()
cos = torch.nn.functional.cosine_similarity(out.flatten().unsqueeze(0), ref.flatten().unsqueeze(0)).item()
print(f'FMHA v3 n={n} V=ones: cosine {cos:.6f} {"PASS" if cos >= 0.99 else "FAIL"}')
if cos < 0.99:
print(f' out[0,:4]={out[0,:4].tolist()}')
print(f' ref[0,:4]={ref[0,:4].tolist()}')
print(f' out[0,:4]={out[0,:4].tolist()} ref[0,:4]={ref[0,:4].tolist()}')
if __name__ == '__main__':
test()
test()

View File

@@ -1,8 +1,44 @@
"""
FMHA v3: QK -> softmax -> PV with KV-tile interleaving.
Bug 4b fix (FMHA pattern): P store uses QK C-fragment layout composition,
NOT PV A-fragment layout. Register bridge: FP32 backing (store partition shape)
recast to BF16 view (QK-load layout).
FMHA v3 Stage-C Multi-Tile (paired TMEM/SMEM atoms, reference-style epilogue).
Two structural rules we had to learn the hard way:
(A) Pipeline handle's `.count` is NOT a GMEM tile coordinate. Whatever it is at
runtime (phase, wrapped slot index, internal state), it is not a global
tile counter and TMA copies don't consume it as one. Use the loop
induction variable for GMEM, handle.index for SMEM.
(B) Hand-constructed TMEM load/store atoms (Ld32x32bOp + St32x32bOp built
independently) DO NOT preserve register tile shape across a round-trip.
A no-op TMEM-load-then-TMEM-store visibly corrupts data. Use the paired
atoms from `utils.sm100.get_tmem_load_op` + `get_smem_store_op` — they
are configured together for the same (mma_tiler, layout, dtype) combo
and the register tile shape lines up. This is what the CUTLASS Blackwell
FMHA reference does in `correction_epilog`.
Kernel structure:
1. Combined K+V pipeline (tx_count = K_bytes + V_bytes; one acquire per kt;
K and V share the same barrier slot). SMEM slot via kvh.index, GMEM via
the cutlass.range loop variable.
2. Reference-style epilogue (TMEM → reg → scale by 1/row_sum → FP32→BF16 in
reg → SMEM via paired atoms → TMA SMEM→GMEM). One pass, no TMEM
round-trip, no `epilogue_tma_store` helper. Inline TMA store + named
barrier sync to substitute for what the helper would have done.
3. Online softmax row_max / row_sum tracking is correct, but the per-tile
in-place TMEM O rescale (multiplying existing O by exp2(old_max - new_max)
before PV[kt]) is currently DISABLED. Fixing that requires applying the
same paired-atom pattern to a separate scratch SMEM buffer and bouncing
PV's accumulator through it, which is substantial work. For now, the
kernel is correct when row_max growth across tiles is mild. Long n with
pronounced max growth will drift; the fix path is well-defined.
4. final_o_bar (32 MMA + 128 softmax threads). MMA arrives between
acc_pipe.producer_commit and producer_tail; softmax arrives_and_waits
before reading O. Order: producer_commit → final_o_bar.arrive() →
producer_tail (reverse deadlocks).
"""
import torch, cutlass, cutlass.cute as cute, cutlass.utils as utils, cutlass.pipeline as pipeline
from cutlass.cute.nvgpu import cpasync, tcgen05
@@ -11,11 +47,16 @@ from cutlass.utils import LayoutEnum
from cutlass.utils.tmem_allocator import find_tmem_tensor_col_offset
import cuda.bindings.driver as cuda
import cutlass.torch as ct
import math
HEAD_DIM = 64
class FmhaV3:
def __init__(self):
class FmhaV3StageCMulti:
def __init__(self, s_k=128, scale_softmax=None):
# s_k MUST equal actual sequence length n.
self.s_k = s_k
self.n_kv_tiles = s_k // 128
self.acc_dtype = Float32; self.qk_acc_dtype = Float32
self.q_dtype = BFloat16; self.o_dtype = BFloat16; self.c_dtype = BFloat16
self.use_2cta_instrs = False; self.epilog_sync_bar_id = 1
@@ -23,6 +64,8 @@ class FmhaV3:
self.epilogue_warp_id = (0,1,2,3); self.mma_warp_id = 4; self.tma_warp_id = 5
self.threads_per_cta = 192; self.num_c_stage = 2
self.kv_stage = 2; self.q_stage = 1; self.num_c_stage = 2
self.scale_softmax = scale_softmax if scale_softmax is not None else 1.0 / math.sqrt(HEAD_DIM)
self.scale_softmax_log2 = self.scale_softmax * math.log2(math.e)
def _setup(self, qk_mma, pv_mma):
qk_ik = cute.size(qk_mma.shape_mnk, mode=[2])
@@ -45,36 +88,35 @@ class FmhaV3:
pv_thr = pv_mma.get_slice(0); pv_as = pv_thr.partition_shape_C(self.pv_mma_tiler[:2])
tOtO = pv_thr.make_fragment_C(pv_as)
self.tmem_s0_offset = 0; self.tmem_p0_offset = 32
# P occupies [tmem_p0_offset, tmem_p0_offset + p_cols_fp32)
# S occupies [0, qk_mma_tiler[1]) = [0, 128)
# O must NOT overlap P. Place O after max(S end, P end), aligned to 32.
p_cols_fp32 = self.pv_mma_tiler[2] * self.q_dtype.width // self.qk_acc_dtype.width
p_end = self.tmem_p0_offset + p_cols_fp32 # 32 + 64 = 96
s_cols = self.qk_mma_tiler[1] # 128
o_after = max(s_cols, p_end) # 128
self.tmem_o0_offset = ((o_after + 31) // 32) * 32 # align to 32 = 128
o_cols = find_tmem_tensor_col_offset(tOtO) # footprint of O
p_end = self.tmem_p0_offset + p_cols_fp32
s_cols = self.qk_mma_tiler[1]
o_after = max(s_cols, p_end)
self.tmem_o0_offset = ((o_after + 31) // 32) * 32
o_cols = find_tmem_tensor_col_offset(tOtO)
total = self.tmem_o0_offset + o_cols
# Must be multiple of 32 AND power of 2
self.num_tmem_alloc_cols = 1
while self.num_tmem_alloc_cols < total:
self.num_tmem_alloc_cols *= 2
cta = cute.size(qk_mma.thr_id.shape)
q_s = cute.slice_(self.q_smem_s,(None,None,None,0)); k_s = cute.slice_(self.k_smem_s,(None,None,None,0))
q_s = cute.slice_(self.q_smem_s,(None,None,None,0))
k_s = cute.slice_(self.k_smem_s,(None,None,None,0))
v_s = cute.slice_(self.v_smem_s,(None,None,None,0))
self.q_tx_bytes = cute.size_in_bytes(self.q_dtype, q_s) * cta
self.kv_tx_bytes = cute.size_in_bytes(self.q_dtype, k_s) * cta
# Combined barrier: tx_count covers BOTH K and V transfers per acquire.
self.kv_tx_bytes = (cute.size_in_bytes(self.q_dtype, k_s) +
cute.size_in_bytes(self.q_dtype, v_s)) * cta
@cute.jit
def __call__(self, q, k, v, c, stream):
self.q_dtype = q.element_type; self.o_dtype = c.element_type; self.c_dtype = self.o_dtype
self.a_major = LayoutEnum.from_tensor(q).mma_major_mode()
self.b_major = LayoutEnum.from_tensor(k).mma_major_mode()
# FMHA-style V: reconstruct as (HEAD_DIM, s_k, 1) MN-major
v_fmha = cute.make_tensor(
v.iterator,
cute.make_layout(
(HEAD_DIM, 128, 1),
stride=(1, HEAD_DIM, HEAD_DIM * 128),
(HEAD_DIM, self.s_k, 1),
stride=(1, HEAD_DIM, HEAD_DIM * self.s_k),
),
)
self.v_major = LayoutEnum.from_tensor(v_fmha).mma_major_mode()
@@ -107,9 +149,13 @@ class FmhaV3:
smem = utils.SmemAllocator(); st = smem.allocate(SS)
qp,qc = pipeline.PipelineTmaUmma.create(barrier_storage=st.q_bar.data_ptr(),num_stages=self.q_stage,producer_group=pipeline.CooperativeGroup(pipeline.Agent.Thread),consumer_group=pipeline.CooperativeGroup(pipeline.Agent.Thread,1),tx_count=self.q_tx_bytes,cta_layout_vmnk=cl_vmnk,defer_sync=True).make_participants()
# Combined K+V pipeline: each stage carries BOTH K and V loaded together.
kvp,kvc = pipeline.PipelineTmaUmma.create(barrier_storage=st.kv_bar.data_ptr(),num_stages=self.kv_stage,producer_group=pipeline.CooperativeGroup(pipeline.Agent.Thread),consumer_group=pipeline.CooperativeGroup(pipeline.Agent.Thread,1),tx_count=self.kv_tx_bytes,cta_layout_vmnk=cl_vmnk,defer_sync=True).make_participants()
s_prod,s_cons = pipeline.PipelineUmmaAsync.create(barrier_storage=st.s_bar.data_ptr(),num_stages=1,producer_group=pipeline.CooperativeGroup(pipeline.Agent.Thread),consumer_group=pipeline.CooperativeGroup(pipeline.Agent.Thread,32*len(self.epilogue_warp_id))).make_participants()
softmax_done_bar = pipeline.NamedBarrier(barrier_id=3, num_threads=32 + 32*len(self.epilogue_warp_id))
# Final-O sync: MMA arrives between producer_commit and producer_tail;
# softmax arrives_and_waits before reading O for the final normalize.
final_o_bar = pipeline.NamedBarrier(barrier_id=4, num_threads=32 + 32*len(self.epilogue_warp_id))
acc_pipe = pipeline.PipelineUmmaAsync.create(barrier_storage=st.acc_bar.data_ptr(),num_stages=self.num_acc_stage,producer_group=pipeline.CooperativeGroup(pipeline.Agent.Thread),consumer_group=pipeline.CooperativeGroup(pipeline.Agent.Thread,len(self.epilogue_warp_id)),cta_layout_vmnk=cl_vmnk,defer_sync=True)
tmem_bar = pipeline.NamedBarrier(barrier_id=2,num_threads=32*len((self.mma_warp_id,*self.epilogue_warp_id)))
tmem = utils.TmemAllocator(st.holding.ptr,barrier_for_retrieve=tmem_bar,allocator_warp_id=self.epilogue_warp_id[0],is_two_cta=cute.size(qk_mma.thr_id.shape)==2,two_cta_tmem_dealloc_mbar_ptr=st.tmem_dealloc.ptr)
@@ -134,7 +180,7 @@ class FmhaV3:
b_lay = cute.make_layout(cute.slice_(cl_vmnk,(0,None,0,0)).shape)
tBsK,tBgK = cpasync.tma_partition(tma_k,0,b_lay,cute.group_modes(sK,0,3),cute.group_modes(tCgK,0,3))
tVsV,tVgV = cpasync.tma_partition(tma_v,0,b_lay,cute.group_modes(sV,0,3),cute.group_modes(tCgV,0,3))
tAgQ = tAgQ[(None,0,None,0)]; tBgK = tBgK[(None,0,None,0)]; tVgV = tVgV[(None,0,None,0)]
tAgQ = tAgQ[(None,0,None,0)]; tBgK = tBgK[(None,None,0,0)]; tVgV = tVgV[(None,0,None,0)]
tCrQ = qk_mma.make_fragment_A(sQ); tCrK = qk_mma.make_fragment_B(sK)
tCrV = pv_mma.make_fragment_B(sV)
@@ -146,7 +192,6 @@ class FmhaV3:
tOtO = pv_thr.make_fragment_C(pv_as)
tOtO0 = cute.make_tensor(tOtO.iterator + self.tmem_o0_offset, tOtO.layout)
# --- PV read view (for MMA only, NOT for softmax store) ---
tP = cute.make_tensor(tStS.iterator, p_tmem_s.outer)
tOrP_base = pv_thr.make_fragment_A(tP)
tOrP = tOrP_base[(None,None,None,0)]
@@ -158,22 +203,25 @@ class FmhaV3:
tCtO_fake = pv_mma.make_fragment_C(cute.append(pv_as, self.num_acc_stage))
pipeline.pipeline_init_wait(cluster_shape_mn=cl_vmnk)
# TMA LOAD
# ===== TMA LOAD warp =====
# NOTE: using kt from cutlass.range works for n=128 (single tile).
# Multi-tile (n>128) loads from tile 0 only — the JIT constant-folds kt.
# TODO: fix multi-tile TMA indexing (kv_coord pattern from diag test).
if warp_idx == self.tma_warp_id:
qp.reset(); qh = qp.acquire_and_advance()
cute.copy(tma_q,tAgQ[(None,qh.count)],tAsQ[(None,qh.index)],tma_bar_ptr=qh.barrier)
cute.copy(tma_q, tAgQ[(None, Int32(0))], tAsQ[(None, qh.index)], tma_bar_ptr=qh.barrier)
qp.tail()
kvp.reset(); pk = kvp.try_acquire()
for kt in cutlass.range(n_kv_tiles,unroll=1):
kh = kvp.acquire_and_advance(pk)
cute.copy(tma_k,tBgK[(None,kh.count)],tBsK[(None,kh.index)],tma_bar_ptr=kh.barrier)
pk = cutlass.Boolean(1)
vh = kvp.acquire_and_advance(pk)
cute.copy(tma_v,tVgV[(None,vh.count)],tVsV[(None,vh.index)],tma_bar_ptr=vh.barrier)
for kt in cutlass.range(0, n_kv_tiles, 1, unroll=1):
kvh = kvp.acquire_and_advance(pk)
cute.copy(tma_k, tBgK[(None, kt)], tBsK[(None, kvh.index)], tma_bar_ptr=kvh.barrier)
cute.copy(tma_v, tVgV[(None, kt)], tVsV[(None, kvh.index)], tma_bar_ptr=kvh.barrier)
pk = cutlass.Boolean(1)
kvp.tail()
# MMA
# ===== MMA warp =====
# One wait per kt; same slot index used for both K (QK) and V (PV).
# Release happens AFTER PV — combined slot stays held across QK+PV.
if warp_idx == self.mma_warp_id:
tmem.wait_for_alloc()
qc.reset(); qh = qc.wait_and_advance(); qh.release()
@@ -181,147 +229,269 @@ class FmhaV3:
acc_st = pipeline.make_pipeline_state(pipeline.PipelineUserType.Producer, self.num_acc_stage)
acc_pipe.producer_acquire(acc_st)
for kt in range(n_kv_tiles):
kh = kvc.wait_and_advance(pk); pk = cutlass.Boolean(1)
kvh = kvc.wait_and_advance(pk); pk = cutlass.Boolean(1)
sh = s_prod.acquire_and_advance()
qk_mma.set(tcgen05.Field.ACCUMULATE, False)
for kb in cutlass.range(cute.size(tCrQ,mode=[2]), unroll_full=True):
cute.gemm(qk_mma, tStS0, tCrQ[(None,None,kb,0)], tCrK[(None,None,kb,kh.index)], tStS0)
for kb in cutlass.range(cute.size(tCrQ, mode=[2]), unroll_full=True):
cute.gemm(qk_mma, tStS0, tCrQ[(None,None,kb,0)], tCrK[(None,None,kb,kvh.index)], tStS0)
qk_mma.set(tcgen05.Field.ACCUMULATE, True)
cute.arch.fence_view_async_tmem_store()
sh.commit(); kh.release()
sh.commit()
softmax_done_bar.arrive_and_wait()
vh = kvc.wait_and_advance(pk); pk = cutlass.Boolean(1)
pv_mma.set(tcgen05.Field.ACCUMULATE, kt != 0)
for kb in cutlass.range(cute.size(tOrP0,mode=[2]), unroll_full=True):
cute.gemm(pv_mma, tOtO0, tOrP0[(None,None,kb)], tCrV[(None,None,kb,vh.index)], tOtO0)
for kb in cutlass.range(cute.size(tOrP0, mode=[2]), unroll_full=True):
cute.gemm(pv_mma, tOtO0, tOrP0[(None,None,kb)], tCrV[(None,None,kb,kvh.index)], tOtO0)
pv_mma.set(tcgen05.Field.ACCUMULATE, True)
cute.arch.fence_view_async_tmem_store()
vh.release()
kvh.release()
acc_pipe.producer_commit(acc_st); acc_st.advance()
# Signal softmax FIRST so it can run normalize + epilogue. Then
# wait for the epilogue's consumer-release in producer_tail.
# Reverse order deadlocks: producer_tail blocks waiting for
# consumer release; softmax blocks at final_o_bar waiting for
# MMA arrive; the epilogue (which does the release) is gated
# behind softmax's final_o_bar wait. Cycle.
final_o_bar.arrive()
acc_pipe.producer_tail(acc_st)
# EPILOGUE
# ===== SOFTMAX + EPILOGUE warps =====
if warp_idx < self.mma_warp_id:
tmem.allocate(self.num_tmem_alloc_cols)
tmem.wait_for_alloc()
tmem_ptr = tmem.retrieve_ptr(self.qk_acc_dtype)
sfw_idx = tidx % (32 * len(self.epilogue_warp_id))
# --- S load (QK C-fragment layout) ---
# S load
tmem_load_atom = cute.make_copy_atom(tcgen05.copy.Ld32x32bOp(tcgen05.copy.Repetition(32)), self.qk_acc_dtype)
tiled_tmem_load = tcgen05.make_tmem_copy(tmem_load_atom, tStS0)
thr_load = tiled_tmem_load.get_slice(sfw_idx)
tTMEM_LOADtS = thr_load.partition_S(tStS0)
# S coordinate tensor (QK C-fragment)
cS = cute.make_identity_tensor((self.qk_mma_tiler[0], self.qk_mma_tiler[1]))
tScS = qk_thr.partition_C(cS)
tTMEM_LOADcS = thr_load.partition_D(tScS)
# --- P store (QK C-fragment layout composition, FMHA pattern) ---
# P logical columns = PV K = QK N = pv_mma_tiler[2]
# Packed FP32 columns: BF16 pairs packed into FP32 words
# P store
p_cols_fp32 = self.pv_mma_tiler[2] * self.q_dtype.width // self.qk_acc_dtype.width
# BF16: 128 * 16 / 32 = 64
# P TMEM destination: QK C-fragment layout composed with P sub-tile
tStP_layout = cute.composition(
tStS.layout,
cute.make_layout((self.pv_mma_tiler[0], p_cols_fp32)),
)
tStP0 = cute.make_tensor(
tStS.iterator + self.tmem_p0_offset,
tStP_layout,
)
# P TMEM store atom and tiled copy
tmem_store_atom = cute.make_copy_atom(
tcgen05.copy.St32x32bOp(tcgen05.copy.Repetition(32)),
self.qk_acc_dtype,
)
tStP_layout = cute.composition(tStS.layout, cute.make_layout((self.pv_mma_tiler[0], p_cols_fp32)))
tStP0 = cute.make_tensor(tStS.iterator + self.tmem_p0_offset, tStP_layout)
tmem_store_atom = cute.make_copy_atom(tcgen05.copy.St32x32bOp(tcgen05.copy.Repetition(32)), self.qk_acc_dtype)
tiled_tmem_store = tcgen05.make_tmem_copy(tmem_store_atom, tStP0)
thr_store = tiled_tmem_store.get_slice(sfw_idx)
tTMEM_STOREtP = thr_store.partition_D(tStP0)
# P coordinate tensor: QK C-fragment coordinate composed with P sub-tile
tScP_layout = cute.composition(
tScS.layout,
cute.make_layout((self.pv_mma_tiler[0], p_cols_fp32)),
)
tScP_layout = cute.composition(tScS.layout, cute.make_layout((self.pv_mma_tiler[0], p_cols_fp32)))
tScP = cute.make_tensor(tScS.iterator, tScP_layout)
tTMEM_STOREcP = thr_store.partition_S(tScP)
row_max = -Float32.inf
row_sum = Float32(0.0)
scale_log2 = Float32(self.scale_softmax_log2)
# Per-tile softmax loop.
# Online softmax row_max/row_sum tracking is maintained, but the
# in-place TMEM O rescale (which would multiply existing O by
# exp2(old_max - new_max) before PV[kt]) is DISABLED — this is the
# correctness compromise for hand-paired TMEM atoms not working.
# The fix path is to integrate the rescale into the same paired
# tmem_load/smem_store epilogue pattern we use below for normalize.
# For now: kernel is correct when row_max growth across tiles is
# mild (typical for short n with random data); for very long n
# the missing rescale shows as accuracy drift.
for kt in range(n_kv_tiles):
si_handle = s_cons.wait_and_advance()
# Load S from TMEM (FP32, QK C-fragment layout)
# Load S[kt]
tTMEM_LOADrS = cute.make_rmem_tensor(tTMEM_LOADcS.shape, self.qk_acc_dtype)
cute.copy(tiled_tmem_load, tTMEM_LOADtS, tTMEM_LOADrS)
cute.arch.fence_view_async_tmem_load()
# Register bridge (FMHA pattern):
# rP_words: FP32 backing store with store-partition shape
# rP_bf16: BF16 view over same registers using QK-load layout
rP_words = cute.make_rmem_tensor(tTMEM_STOREcP.shape, self.qk_acc_dtype)
rP_bf16 = cute.make_tensor(
cute.recast_ptr(rP_words.iterator, dtype=self.q_dtype),
tTMEM_LOADrS.layout,
)
# Fragmented load→convert→store:
# Load S as FP32, convert to BF16, store through rP_bf16 view
# Pass 1: update row_max (in log2-domain, fused with scale).
old_row_max = row_max
frg_cnt = 4
frg_tile = cute.size(tTMEM_LOADrS) // frg_cnt
tTMEM_LOADrS_frg = cute.logical_divide(tTMEM_LOADrS, cute.make_layout(frg_tile))
for j in range(frg_cnt):
for k in range(cute.size(tTMEM_LOADrS_frg, mode=[0])):
row_max = cute.arch.fmax(row_max, tTMEM_LOADrS_frg[k, j] * scale_log2)
row_max_safe = row_max
if row_max == -cutlass.Float32.inf:
row_max_safe = Float32(0.0)
# row_sum rescale (correct even without O rescale — row_sum
# is a register variable, not in TMEM).
# row_max is already in scaled domain, so no extra scale_log2.
acc_scale_ = old_row_max - row_max_safe
acc_scale = cute.math.exp2(acc_scale_, fastmath=True)
if old_row_max == -cutlass.Float32.inf:
acc_scale = Float32(0.0)
row_sum *= acc_scale
# Pass 2: P = exp2((S - new_max) * log2), accumulate row_sum,
# store BF16 P through the FP32-backed register bridge.
rP_words = cute.make_rmem_tensor(tTMEM_STOREcP.shape, self.qk_acc_dtype)
rP_bf16 = cute.make_tensor(cute.recast_ptr(rP_words.iterator, dtype=self.q_dtype), tTMEM_LOADrS.layout)
minus_row_max = Float32(0.0) - row_max_safe
rP_bf16_frg = cute.logical_divide(rP_bf16, cute.make_layout(frg_tile))
for j in range(frg_cnt):
for k in range(cute.size(tTMEM_LOADrS_frg, mode=[0])):
tTMEM_LOADrS_frg[k, j] = tTMEM_LOADrS_frg[k, j] * scale_log2 + minus_row_max
tTMEM_LOADrS_frg[k, j] = cute.math.exp2(tTMEM_LOADrS_frg[k, j], fastmath=True)
row_sum = row_sum + tTMEM_LOADrS_frg[k, j]
s_vec = tTMEM_LOADrS_frg[None, j].load()
rP_bf16_frg[None, j].store(s_vec.to(self.q_dtype))
# Copy packed FP32 backing registers to TMEM
cute.copy(tiled_tmem_store, rP_words, tTMEM_STOREtP)
cute.arch.fence_view_async_tmem_store()
si_handle.release()
softmax_done_bar.arrive()
# === Reference-style scaled epilogue (no TMEM round-trip) ===
#
# Pattern (mirrors CUTLASS Blackwell FMHA reference's
# correction_epilog): for each column sub-tile,
# 1. TMEM -> registers via PAIRED tmem_load atom
# 2. scale in registers (1/row_sum)
# 3. FP32 -> BF16 conversion in registers
# 4. registers -> SMEM via PAIRED smem_store atom
# Then TMA SMEM -> GMEM as a separate step.
#
# Critical: the load and store atoms MUST be a matched pair.
# Independently constructed Ld32x32bOp + St32x32bOp atoms (the
# previous code) don't preserve the register tile shape, so even a
# no-op load+store corrupts data. Using utils.blackwell_helpers
# (sm100_utils) gives a paired set keyed to the same epi_subtile.
# Wait for MMA's PV[N-1] to commit before reading O.
final_o_bar.arrive_and_wait()
# === O normalization via TMEM load → scale → TMEM store ===
# Matches CUTLASS reference's correction_rescale pattern exactly.
corr_tile_size = 16
cO = cute.make_identity_tensor((self.pv_mma_tiler[0], self.pv_mma_tiler[1]))
tOcO = pv_thr.partition_C(cO)
tOtO_i_layout = cute.composition(tOtO0.layout, cute.make_layout((128, corr_tile_size)))
tOcO_i_layout = cute.composition(tOcO.layout, cute.make_layout((128, corr_tile_size)))
tOtO_i = cute.make_tensor(tOtO0.iterator, tOtO_i_layout)
tOcO_i = cute.make_tensor(tOcO.iterator, tOcO_i_layout)
tmem_load_atom = cute.make_copy_atom(
tcgen05.copy.Ld32x32bOp(tcgen05.copy.Repetition(corr_tile_size)),
self.acc_dtype,
)
tmem_store_atom = cute.make_copy_atom(
tcgen05.copy.St32x32bOp(tcgen05.copy.Repetition(corr_tile_size)),
self.acc_dtype,
)
tiled_tmem_load_o = tcgen05.make_tmem_copy(tmem_load_atom, tOtO_i)
tiled_tmem_store_o = tcgen05.make_tmem_copy(tmem_store_atom, tOtO_i)
thr_tmem_load_o = tiled_tmem_load_o.get_slice(sfw_idx)
thr_tmem_store_o = tiled_tmem_store_o.get_slice(sfw_idx)
tTMEM_LOADtO = thr_tmem_load_o.partition_S(tOtO_i)
tTMEM_LOADcO = thr_tmem_load_o.partition_D(tOcO_i)
tTMEM_STOREtO = thr_tmem_store_o.partition_D(tOtO_i)
# 2D register tensor: (frg_shape, n_corr_tiles)
tTMrO = cute.make_rmem_tensor(
(tTMEM_LOADcO.shape, 128 // corr_tile_size), self.acc_dtype
)
inv_row_sum = Float32(1.0) / row_sum
for i in range(HEAD_DIM // corr_tile_size):
tTMrO_i_ = tTMrO[None, i]
tTMrO_i_layout = cute.composition(
tTMrO_i_.layout, cute.make_layout(tTMrO.shape[0])
)
tTMrO_i = cute.make_tensor(tTMrO_i_.iterator, tTMrO_i_layout)
tTMEM_LOADtO_i = cute.make_tensor(
tTMEM_LOADtO.iterator + i * corr_tile_size, tTMEM_LOADtO.layout
)
tTMEM_STOREtO_i = cute.make_tensor(
tTMEM_STOREtO.iterator + i * corr_tile_size, tTMEM_STOREtO.layout
)
cute.copy(tiled_tmem_load_o, tTMEM_LOADtO_i, tTMrO_i)
for j in cutlass.range(cute.size(tTMrO_i), vectorize=True):
tTMrO_i[j] = tTMrO_i[j] * inv_row_sum
cute.copy(tiled_tmem_store_o, tTMrO_i, tTMEM_STOREtO_i)
cute.arch.fence_view_async_tmem_store()
# Standard epilogue: TMEM → SMEM → GMEM via TMA store.
# O in TMEM is now scaled by 1/row_sum.
tCtO_base = cute.make_tensor(tmem_ptr + self.tmem_o0_offset, tCtO_fake.layout)
acc_cons_st = pipeline.make_pipeline_state(pipeline.PipelineUserType.Consumer, self.num_acc_stage)
acc_cons_st = pipeline.make_pipeline_state(
pipeline.PipelineUserType.Consumer, self.num_acc_stage
)
c_grp = pipeline.CooperativeGroup(pipeline.Agent.Thread, 32 * len(self.epilogue_warp_id))
c_pipe = pipeline.PipelineTmaStore.create(num_stages=self.num_c_stage, producer_group=c_grp)
acc_cons_st = utils.gemm.sm100.epilogue_tma_store(self, tidx, warp_idx, tma_c, tCtO_base, sC, tCgC, epi_tile, 0, const_expr(lambda x: x), (0,0,0), acc_cons_st, acc_pipe, c_pipe)
acc_cons_st = utils.gemm.sm100.epilogue_tma_store(
self, tidx, warp_idx, tma_c, tCtO_base, sC, tCgC, epi_tile,
0, const_expr(lambda x: x), (0, 0, 0),
acc_cons_st, acc_pipe, c_pipe,
)
c_pipe.producer_tail()
tmem.relinquish_alloc_permit()
tmem.free(tmem_ptr)
def test():
torch.manual_seed(42)
for n in [128]:
for n in [128, 256, 512, 1024]:
torch.manual_seed(42)
m, hd = 128, HEAD_DIM
q = torch.randn(m, hd, 1, dtype=torch.bfloat16, device='cuda')
k = torch.randn(n, hd, 1, dtype=torch.bfloat16, device='cuda')
v = torch.randn(n, hd, dtype=torch.bfloat16, device='cuda')
# V passed as (n, hd) row-major — FMHA-style reconstruction inside kernel
v_kernel = v.unsqueeze(-1)
c = torch.zeros(m, hd, 1, dtype=torch.bfloat16, device='cuda')
qf = q[:,:,0].float(); kf = k[:,:,0].float()
ref = (qf @ kf.T).bfloat16().float() @ v.float()
qf = q[:, :, 0].float()
kf = k[:, :, 0].float()
scale = 1.0 / math.sqrt(hd)
attn = qf @ kf.T * scale
attn = torch.softmax(attn, dim=-1)
ref = attn @ v.float()
mQ = ct.from_dlpack(q).mark_layout_dynamic(leading_dim=ct.get_leading_dim(q))
mK = ct.from_dlpack(k).mark_layout_dynamic(leading_dim=ct.get_leading_dim(k))
mV = ct.from_dlpack(v_kernel).mark_layout_dynamic(leading_dim=ct.get_leading_dim(v_kernel))
mC = ct.from_dlpack(c).mark_layout_dynamic(leading_dim=ct.get_leading_dim(c))
stream = cuda.CUstream(torch.cuda.current_stream().cuda_stream)
kernel = FmhaV3()
# Each n requires its own compiled kernel (s_k is compile-time).
kernel = FmhaV3StageCMulti(s_k=n)
print(f'n={n}: Compiling...', flush=True)
compiled = cute.compile(kernel, mQ, mK, mV, mC, stream)
print(f'n={n}: tmem_offsets: s0={kernel.tmem_s0_offset} p0={kernel.tmem_p0_offset} o0={kernel.tmem_o0_offset} alloc={kernel.num_tmem_alloc_cols}', flush=True)
print(f'n={n}: Running...', flush=True)
print(f'n={n}: tmem s0={kernel.tmem_s0_offset} p0={kernel.tmem_p0_offset} '
f'o0={kernel.tmem_o0_offset} alloc={kernel.num_tmem_alloc_cols} '
f'kv_tx_bytes={kernel.kv_tx_bytes}', flush=True)
compiled(mQ, mK, mV, mC, stream)
torch.cuda.synchronize()
out = c[:,:,0].float()
cos = torch.nn.functional.cosine_similarity(out.flatten().unsqueeze(0), ref.flatten().unsqueeze(0)).item()
print(f'FMHA v3 n={n} V=ones: cosine {cos:.6f} {"PASS" if cos >= 0.99 else "FAIL"}')
out = c[:, :, 0].float()
cos = torch.nn.functional.cosine_similarity(
out.flatten().unsqueeze(0), ref.flatten().unsqueeze(0)
).item()
max_abs = (out - ref).abs().max().item()
n_tiles = n // 128
print(f'FMHA Stage-C Multi n={n} ({n_tiles} kv tiles): '
f'cos {cos:.6f} max_abs {max_abs:.4f} '
f'{"PASS" if cos >= 0.99 else "FAIL"}')
if cos < 0.99:
print(f' out[0,:4]={out[0,:4].tolist()} ref[0,:4]={ref[0,:4].tolist()}')
print(f' out[0,:4]={out[0,:4].tolist()}')
print(f' ref[0,:4]={ref[0,:4].tolist()}')
if __name__ == '__main__':
test()
test()