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chore: import upstream snapshot with attribution
2026-07-13 13:36:25 +08:00

346 lines
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Python

# Licensed to the Apache Software Foundation (ASF) under one
# or more contributor license agreements. See the NOTICE file
# distributed with this work for additional information
# regarding copyright ownership. The ASF licenses this file
# to you under the Apache License, Version 2.0 (the
# "License"); you may not use this file except in compliance
# with the License. You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing,
# software distributed under the License is distributed on an
# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
# KIND, either express or implied. See the License for the
# specific language governing permissions and limitations
# under the License.
# pylint: disable=invalid-name, too-many-nested-blocks
"""Backend kernels for sampling operator."""
import math
from collections.abc import Callable
import tvm
from tvm.script import tirx as T
from tvm.tirx import PrimFunc
def _is_power_of_two(n: int):
"""Check if n is a power of 2."""
return n > 0 and (n & (n - 1)) == 0
def gpu_multinomial_from_uniform(
prob_dtype: str = "float32",
sample_dtype: str = "float32",
sample_indices_dtype: str = "int64",
dtype: str = "int64",
ty_len: int = 4,
tx_len: int = 32,
thread_elem: int = 4,
eps: float = 1e-6,
) -> PrimFunc:
"""Generate GPU kernel for multinomial_from_uniform operator.
Parameters
----------
ty_len : int
The length of `threadIdx.y`
tx_len : int
The length of `threadIdx.x`
thread_elem : int
The number of elements processed by single thread
prob_dtype : str
The probability data type
sample_dtype : str
The sample data type
sample_indices_dtype : str
The sample indices data type
dtype : str
The output data type
Returns
-------
func : PrimFunc
The generated function
"""
target = tvm.target.Target.current()
target_dtype = "int32" if "webgpu" in str(target) else "int64"
TX = T.int64(tx_len) # threadIdx.x
TY = T.int64(ty_len) # threadIdx.y
# number of elements to be processed by single thread
thread_elem = T.int64(thread_elem)
# number of elements to be processed by single warp
warp_elem = T.int64(tx_len * thread_elem)
# number of elements to be processed by single block(SM)
block_elem = T.int64(tx_len * ty_len * thread_elem)
LOG_TX = T.int64(int(math.log2(tx_len)))
LOG_TY = T.int64(int(math.log2(ty_len)))
if (
not _is_power_of_two(tx_len)
or not _is_power_of_two(ty_len)
or not _is_power_of_two(thread_elem)
):
raise ValueError(
"Configuration of tx_len, ty_len, thread_elem must be power of 2,"
f"but got {tx_len}, {ty_len}, {thread_elem}"
)
@T.macro
def block_cumsum(
ty: T.int64,
tx: T.int64,
source_local: T.Buffer,
output_shared: T.Buffer,
):
"""cumsum inside block (SM)"""
# Inclusive scan inside thread
for i in T.unroll(1, thread_elem):
source_local[i] += source_local[i - 1]
# Store data to shared memory
for i in T.vectorized(thread_elem):
output_shared[ty * warp_elem + tx * thread_elem + i] = source_local[i]
# Inclusive scan inside warp
for i in T.unroll(LOG_TX):
for j in T.vectorized(thread_elem):
idx: T.let[T.int64] = ty * warp_elem + tx * thread_elem
if tx >= (1 << i):
output_shared[idx + j] += output_shared[
idx - (1 << i) * thread_elem + thread_elem - 1
]
# Inclusive scan inside block
for i in T.unroll(1, TY):
for j in T.vectorized(thread_elem):
if ty == 0:
idx: T.let[T.int64] = i * warp_elem + tx * thread_elem
output_shared[idx + j] += output_shared[i * warp_elem - 1]
def compare_bool_not_equal(a: T.bool, b: T.bool) -> T.bool:
# Vulkan does not support compare two bool value direct
# return a != b
return T.Cast("int8", a) != T.Cast("int8", b)
@T.macro
def block_adjacent_difference_left(
ty: T.int64,
tx: T.int64,
source_local: T.Buffer,
output_local: T.Buffer,
):
with T.sblock():
shared_buf = T.sblock_alloc_buffer((TX * TY,), "bool", scope="shared")
tx_idx: T.let[T.int64] = ty * TX + tx
shared_buf[tx_idx] = source_local[thread_elem - 1]
output_local[0] = T.if_then_else(
tx_idx != 0,
compare_bool_not_equal(source_local[0], shared_buf[tx_idx - 1]),
source_local[0],
)
for i in T.unroll(1, thread_elem):
output_local[i] = compare_bool_not_equal(source_local[i], source_local[i - 1])
def op_reduce_min(a, b):
return T.min(a, b)
def op_reduce_sum(a, b):
return a + b
@T.macro
def block_reduce_with_mask(
ty: T.int64,
tx: T.int64,
init_value,
data_local: T.Buffer,
output_local: T.Buffer,
dtype: str,
reduce_op: Callable, # T.macro
mask_local: T.Buffer | None = None,
):
with T.sblock():
local_sum = T.sblock_alloc_buffer((), dtype, scope="local")
shared_buf = T.sblock_alloc_buffer((TX * TY,), dtype, scope="shared")
idx: T.let[T.int64] = ty * TX + tx
local_sum[()] = T.Cast(dtype, init_value)
for i in T.unroll(thread_elem):
if mask_local is not None:
if mask_local[i]:
local_sum[()] = reduce_op(local_sum[()], data_local[i])
else:
local_sum[()] = reduce_op(local_sum[()], data_local[i])
shared_buf[idx] = local_sum[()]
for i in T.unroll(LOG_TX + LOG_TY):
if idx % (1 << (i + 1)) == 0:
shared_buf[idx] = reduce_op(shared_buf[idx], shared_buf[idx + (1 << i)])
output_local[()] = shared_buf[0]
@T.macro
def single_batch_sampling(
prob,
row_idx,
vocab_size,
ty,
tx,
step_iter,
threshold,
aggregate,
uniform_sample,
sample_id_local,
):
with T.sblock():
prob_gt_threshold = T.sblock_alloc_buffer((thread_elem,), prob_dtype, scope="local")
cumsum = T.sblock_alloc_buffer((block_elem,), prob_dtype, scope="shared")
greater_than_u = T.sblock_alloc_buffer((thread_elem,), "bool", scope="local")
mask = T.sblock_alloc_buffer((thread_elem,), "bool", scope="local")
valid = T.sblock_alloc_buffer((thread_elem,), "bool", scope="local")
indices = T.sblock_alloc_buffer((thread_elem), dtype, scope="local")
step_aggregate = T.sblock_alloc_buffer((), prob_dtype, scope="local")
# Load prob data from global memory to local memory
for v in T.unroll(thread_elem):
idx: T.let[T.int64] = step_iter * block_elem + ty * warp_elem + tx * thread_elem + v
prob_local: T.let = T.if_then_else(
idx < vocab_size,
prob[row_idx, idx],
T.Cast(prob_dtype, 0),
)
prob_gt_threshold[v] = T.if_then_else(
prob_local > threshold, prob_local, T.Cast(prob_dtype, 0)
)
valid[v] = prob_local > threshold and idx < vocab_size
block_reduce_with_mask(
ty,
tx,
init_value=0,
data_local=prob_gt_threshold,
output_local=step_aggregate,
dtype=prob_dtype,
reduce_op=op_reduce_sum,
mask_local=None,
)
if T.tvm_thread_invariant(aggregate[()] + step_aggregate[()] >= uniform_sample - eps):
block_cumsum(ty, tx, prob_gt_threshold, cumsum)
# Note: it should be `T.vectorized` instead of `T.unroll`
# However, it will cause vulkan codegen error
for v in T.unroll(thread_elem):
greater_than_u[v] = (
cumsum[ty * warp_elem + tx * thread_elem + v] + aggregate[()]
>= uniform_sample - eps
)
block_adjacent_difference_left(ty, tx, greater_than_u, mask)
# Same as above, it should be `T.vectorized`
for v in T.unroll(thread_elem):
mask[v] = mask[v] and valid[v]
indices[v] = step_iter * block_elem + ty * warp_elem + tx * thread_elem + v
block_reduce_with_mask(
ty,
tx,
init_value=vocab_size - 1,
data_local=indices,
output_local=sample_id_local,
dtype=dtype,
reduce_op=op_reduce_min,
mask_local=mask,
)
aggregate[()] += step_aggregate[()]
@T.prim_func(s_tir=True)
def parallel_sampling_from_prob(
var_prob: T.handle,
var_uniform_samples: T.handle,
var_row_indices: T.handle,
var_sampled_token_ids: T.handle,
):
T.func_attr({"tirx.is_scheduled": True})
n, vocab_size, batch_size = T.int64(), T.int64(), T.int64()
# match buffers
prob = T.match_buffer(var_prob, (n, vocab_size), prob_dtype)
uniform_samples = T.match_buffer(var_uniform_samples, (batch_size, 1), sample_dtype)
row_indices = T.match_buffer(var_row_indices, (batch_size, 1), sample_indices_dtype)
token_ids = T.match_buffer(var_sampled_token_ids, (batch_size, 1), dtype)
# local buffers
aggregate = T.sblock_alloc_buffer((), prob_dtype, scope="local")
sample_id_local = T.sblock_alloc_buffer((), dtype, scope="local")
step_iter = T.sblock_alloc_buffer((), "int32", scope="local")
for bx in T.thread_binding(batch_size, thread="blockIdx.x"):
row_idx: T.let[T.int64] = T.Cast("int64", row_indices[bx, 0])
for ty in T.thread_binding(TY, thread="threadIdx.y"):
for tx in T.thread_binding(TX, thread="threadIdx.x"):
u: T.let[T.float32] = uniform_samples[bx, 0]
aggregate[()] = T.Cast(prob_dtype, 0)
step_iter[()] = T.int32(0)
# at least one iteration
while T.tvm_thread_invariant(
(step_iter[()] == 0 or aggregate[()] < u - eps)
and T.Cast(target_dtype, step_iter[()])
< T.Cast(target_dtype, T.ceildiv(vocab_size, block_elem))
):
single_batch_sampling(
prob,
row_idx,
vocab_size,
ty,
tx,
T.Cast(target_dtype, step_iter[()]),
0.0,
aggregate,
u,
sample_id_local,
)
step_iter[()] += 1
if tx == 0 and ty == 0:
token_ids[bx, 0] = sample_id_local[()]
return parallel_sampling_from_prob
def generic_get_sample_index(
prob_dtype: str = "float32",
sample_dtype: str = "float32",
sample_indices_dtype: str = "int64",
dtype: str = "int64",
):
"""Generate a generic get_sample_index kernel."""
@T.prim_func(private=True, s_tir=True)
def _get_sample_index(A: T.handle, B: T.handle, C: T.handle, D: T.handle):
batch, vocab_size = T.int64(), T.int64()
prob = T.match_buffer(A, (batch, vocab_size), prob_dtype)
out_batch = T.int64()
usample = T.match_buffer(B, (out_batch, 1), sample_dtype)
sample_indices = T.match_buffer(C, (out_batch, 1), sample_indices_dtype)
output_index = T.match_buffer(D, (out_batch, 1), dtype)
for ax0, ax1 in T.grid(out_batch, vocab_size):
with T.sblock("T_get_sample_index"):
v_ax0, v_ax1 = T.axis.remap("SS", [ax0, ax1])
T.writes(output_index[v_ax0, 0])
if (
usample[v_ax0, T.int64(0)] < prob[sample_indices[v_ax0, T.int64(0)], v_ax1]
or v_ax1 + 1 == vocab_size
):
if v_ax1 == 0:
output_index[v_ax0, 0] = 0
elif (
usample[v_ax0, T.int64(0)]
>= prob[sample_indices[v_ax0, T.int64(0)], v_ax1 - 1]
):
output_index[v_ax0, 0] = v_ax1
return _get_sample_index