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PyTorch 基准测试#
创建于：2020 年 12 月 2 日 | 最后更新：2023 年 5 月 9 日 | 最后验证：2024 年 11 月 5 日
本秘籍提供了一个快速入门指南，介绍如何使用 PyTorch benchmark 模块来衡量和比较代码性能。
简介#
基准测试是编写代码的重要一步。它帮助我们验证代码是否符合性能预期，比较解决相同问题的不同方法，并防止性能回归。
在对 PyTorch 代码进行基准测试时有许多选项，包括 Python 内置的 timeit 模块。然而，对 PyTorch 代码进行基准测试有许多容易被忽视的注意事项，例如管理线程数量和同步 CUDA 设备。此外，为基准测试生成 Tensor 输入可能非常繁琐。
本秘籍演示了如何使用 PyTorch benchmark 模块来避免常见错误，同时更轻松地比较不同代码的性能、为基准测试生成输入等。
设置#
在我们开始之前，如果尚未安装，请安装 torch。
pip install torch
步骤#
定义要进行基准测试的函数
使用
timeit.Timer进行基准测试使用
torch.utils.benchmark.Timer进行基准测试使用
Blocked Autorange进行基准测试比较基准测试结果
保存/加载基准测试结果
使用
Fuzzed Parameters生成输入使用
Callgrind收集指令计数
1. 定义要进行基准测试的函数#
截至本文撰写时，torch.dot 不支持批处理模式，因此我们将比较两种使用现有 torch 运算符实现它的方法：一种方法结合使用 mul 和 sum，而另一种方法将问题简化为 bmm。
import torch
def batched_dot_mul_sum(a, b):
'''Computes batched dot by multiplying and summing'''
return a.mul(b).sum(-1)
def batched_dot_bmm(a, b):
'''Computes batched dot by reducing to ``bmm``'''
a = a.reshape(-1, 1, a.shape[-1])
b = b.reshape(-1, b.shape[-1], 1)
return torch.bmm(a, b).flatten(-3)
# Input for benchmarking
x = torch.randn(10000, 64)
# Ensure that both functions compute the same output
assert batched_dot_mul_sum(x, x).allclose(batched_dot_bmm(x, x))
2. 使用 timeit.Timer 进行基准测试#
首先，让我们使用 Python 内置的 timeit 模块对代码进行基准测试。我们在此处保持基准测试代码简单，以便比较 timeit 和 torch.utils.benchmark 的默认设置。
import timeit
t0 = timeit.Timer(
stmt='batched_dot_mul_sum(x, x)',
setup='from __main__ import batched_dot_mul_sum',
globals={'x': x})
t1 = timeit.Timer(
stmt='batched_dot_bmm(x, x)',
setup='from __main__ import batched_dot_bmm',
globals={'x': x})
print(f'mul_sum(x, x): {t0.timeit(100) / 100 * 1e6:>5.1f} us')
print(f'bmm(x, x): {t1.timeit(100) / 100 * 1e6:>5.1f} us')
输出#
mul_sum(x, x): 111.6 us
bmm(x, x): 70.0 us
3. 使用 torch.utils.benchmark.Timer 进行基准测试#
PyTorch benchmark 模块旨在让那些以前使用过 timeit 模块的人感到熟悉。但是，它的默认设置使其更易于安全地用于 PyTorch 代码的基准测试。我们首先比较与上面相同的基础 API。
import torch.utils.benchmark as benchmark
t0 = benchmark.Timer(
stmt='batched_dot_mul_sum(x, x)',
setup='from __main__ import batched_dot_mul_sum',
globals={'x': x})
t1 = benchmark.Timer(
stmt='batched_dot_bmm(x, x)',
setup='from __main__ import batched_dot_bmm',
globals={'x': x})
print(t0.timeit(100))
print(t1.timeit(100))
输出#
<torch.utils.benchmark.utils.common.Measurement object at 0x7fb10400d0f0>
batched_dot_mul_sum(x, x)
setup: from __main__ import batched_dot_mul_sum
379.29 us
1 measurement, 100 runs , 1 thread
<torch.utils.benchmark.utils.common.Measurement object at 0x7fb103d67048>
batched_dot_bmm(x, x)
setup: from __main__ import batched_dot_bmm
716.42 us
1 measurement, 100 runs , 1 thread
尽管基本功能的 API 相同，但仍存在一些重要差异。benchmark.Timer.timeit() 返回每次运行的时间，而不是像 timeit.Timer.timeit() 那样返回总运行时间。PyTorch benchmark 模块还提供了格式化的字符串表示形式，用于打印结果。
另一个重要差异，也是结果不同的原因，是 PyTorch 基准测试模块默认在单线程中运行。我们可以使用 num_threads 参数更改线程数量。
torch.utils.benchmark.Timer 接受几个额外的参数，包括：label、sub_label、description 和 env，这些参数会更改返回的测量对象的 __repr__，并用于对结果进行分组（稍后会详细介绍）。
num_threads = torch.get_num_threads()
print(f'Benchmarking on {num_threads} threads')
t0 = benchmark.Timer(
stmt='batched_dot_mul_sum(x, x)',
setup='from __main__ import batched_dot_mul_sum',
globals={'x': x},
num_threads=num_threads,
label='Multithreaded batch dot',
sub_label='Implemented using mul and sum')
t1 = benchmark.Timer(
stmt='batched_dot_bmm(x, x)',
setup='from __main__ import batched_dot_bmm',
globals={'x': x},
num_threads=num_threads,
label='Multithreaded batch dot',
sub_label='Implemented using bmm')
print(t0.timeit(100))
print(t1.timeit(100))
输出#
Benchmarking on 40 threads
<torch.utils.benchmark.utils.common.Measurement object at 0x7fb103d54080>
Multithreaded batch dot: Implemented using mul and sum
setup: from __main__ import batched_dot_mul_sum
118.47 us
1 measurement, 100 runs , 40 threads
<torch.utils.benchmark.utils.common.Measurement object at 0x7fb16935d2e8>
Multithreaded batch dot: Implemented using bmm
setup: from __main__ import batched_dot_bmm
68.21 us
1 measurement, 100 runs , 40 threads
使用所有可用线程运行 benchmark 会得到与 timeit 模块类似的结果。更重要的是，哪个版本更快取决于我们运行代码的线程数量。这就是为什么使用代表实际用例的线程设置进行代码基准测试很重要的原因。另一个需要记住的重要事项是在 GPU 上进行基准测试时同步 CPU 和 CUDA。让我们在 CUDA 张量上再次运行上述基准测试，看看会发生什么。
x = torch.randn(10000, 1024, device='cuda')
t0 = timeit.Timer(
stmt='batched_dot_mul_sum(x, x)',
setup='from __main__ import batched_dot_mul_sum',
globals={'x': x})
t1 = timeit.Timer(
stmt='batched_dot_bmm(x, x)',
setup='from __main__ import batched_dot_bmm',
globals={'x': x})
# Ran each twice to show difference before/after warm-up
print(f'mul_sum(x, x): {t0.timeit(100) / 100 * 1e6:>5.1f} us')
print(f'mul_sum(x, x): {t0.timeit(100) / 100 * 1e6:>5.1f} us')
print(f'bmm(x, x): {t1.timeit(100) / 100 * 1e6:>5.1f} us')
print(f'bmm(x, x): {t1.timeit(100) / 100 * 1e6:>5.1f} us')
输出#
mul_sum(x, x): 27.6 us
mul_sum(x, x): 25.3 us
bmm(x, x): 2775.5 us
bmm(x, x): 22.4 us
t0 = benchmark.Timer(
stmt='batched_dot_mul_sum(x, x)',
setup='from __main__ import batched_dot_mul_sum',
globals={'x': x})
t1 = benchmark.Timer(
stmt='batched_dot_bmm(x, x)',
setup='from __main__ import batched_dot_bmm',
globals={'x': x})
# Run only once since benchmark module does warm-up for us
print(t0.timeit(100))
print(t1.timeit(100))
输出#
<torch.utils.benchmark.utils.common.Measurement object at 0x7fb10400d080>
batched_dot_mul_sum(x, x)
setup: from __main__ import batched_dot_mul_sum
232.93 us
1 measurement, 100 runs , 1 thread
<torch.utils.benchmark.utils.common.Measurement object at 0x7fb10400d0f0>
batched_dot_bmm(x, x)
setup: from __main__ import batched_dot_bmm
181.04 us
1 measurement, 100 runs , 1 thread
结果揭示了一些有趣的事情。使用 timeit 模块的 bmm 版本的第一次运行比第二次运行花费的时间长得多。这是因为 bmm 调用 cuBLAS，而 cuBLAS 在第一次调用时需要加载，这需要一些时间。这就是为什么在进行基准测试之前进行预热运行很重要的原因，幸运的是，PyTorch 的 benchmark 模块会为我们处理这个问题。
timeit 和 benchmark 模块之间结果的差异是因为 timeit 模块没有同步 CUDA，因此只计时启动内核的时间。PyTorch 的 benchmark 模块为我们进行同步。
4. 使用 Blocked Autorange 进行基准测试#
虽然 timeit.Timer.autorange 持续测量至少 0.2 秒，但 torch.utils.benchmark.blocked_autorange 进行多次测量，其总时间至少为 0.2 秒（可通过 min_run_time 参数更改），前提是计时开销是整体测量的一小部分。这是通过首先以增加的每次循环运行次数运行，直到运行时远大于测量开销（这也作为预热），然后进行测量直到达到目标时间来完成的。这具有有用的特性，即它浪费的数据更少，并允许我们计算统计数据以估计测量的可靠性。
m0 = t0.blocked_autorange()
m1 = t1.blocked_autorange()
print(m0)
print(m1)
输出#
<torch.utils.benchmark.utils.common.Measurement object at 0x7fb10400d0f0>
batched_dot_mul_sum(x, x)
setup: from __main__ import batched_dot_mul_sum
231.79 us
1 measurement, 1000 runs , 1 thread
<torch.utils.benchmark.utils.common.Measurement object at 0x7fb10400d080>
batched_dot_bmm(x, x)
setup: from __main__ import batched_dot_bmm
Median: 162.08 us
2 measurements, 1000 runs per measurement, 1 thread
我们还可以检查返回的测量对象的各个统计数据。
print(f"Mean: {m0.mean * 1e6:6.2f} us")
print(f"Median: {m0.median * 1e6:6.2f} us")
输出#
Mean: 231.79 us
Median: 231.79 us
5. 比较基准测试结果#
到目前为止，我们已经将我们的两个批处理点版本与单个输入进行了比较。在实践中，我们希望尝试输入组合以及不同数量的线程。Compare 类有助于以格式化的表格形式显示许多测量结果。它使用上面描述的注释（label、sub_label、num_threads 等）以及 description 来分组和组织表格。让我们使用 Compare 来查看我们的函数在不同输入大小和线程数量下的表现。
from itertools import product
# Compare takes a list of measurements which we'll save in results.
results = []
sizes = [1, 64, 1024, 10000]
for b, n in product(sizes, sizes):
# label and sub_label are the rows
# description is the column
label = 'Batched dot'
sub_label = f'[{b}, {n}]'
x = torch.ones((b, n))
for num_threads in [1, 4, 16, 32]:
results.append(benchmark.Timer(
stmt='batched_dot_mul_sum(x, x)',
setup='from __main__ import batched_dot_mul_sum',
globals={'x': x},
num_threads=num_threads,
label=label,
sub_label=sub_label,
description='mul/sum',
).blocked_autorange(min_run_time=1))
results.append(benchmark.Timer(
stmt='batched_dot_bmm(x, x)',
setup='from __main__ import batched_dot_bmm',
globals={'x': x},
num_threads=num_threads,
label=label,
sub_label=sub_label,
description='bmm',
).blocked_autorange(min_run_time=1))
compare = benchmark.Compare(results)
compare.print()
输出#
[--------------- Batched dot ----------------]
| mul/sum | bmm
1 threads: -----------------------------------
[1, 1] | 5.9 | 11.2
[1, 64] | 6.4 | 11.4
[1, 1024] | 6.7 | 14.2
[1, 10000] | 10.2 | 23.7
[64, 1] | 6.3 | 11.5
[64, 64] | 8.6 | 15.4
[64, 1024] | 39.4 | 204.4
[64, 10000] | 274.9 | 748.5
[1024, 1] | 7.7 | 17.8
[1024, 64] | 40.3 | 76.4
[1024, 1024] | 432.4 | 2795.9
[1024, 10000] | 22657.3 | 11899.5
[10000, 1] | 16.9 | 74.8
[10000, 64] | 300.3 | 609.4
[10000, 1024] | 23098.6 | 27246.1
[10000, 10000] | 267073.7 | 118823.7
4 threads: -----------------------------------
[1, 1] | 6.0 | 11.5
[1, 64] | 6.2 | 11.2
[1, 1024] | 6.8 | 14.3
[1, 10000] | 10.2 | 23.7
[64, 1] | 6.3 | 16.2
[64, 64] | 8.8 | 18.2
[64, 1024] | 41.5 | 189.1
[64, 10000] | 91.7 | 849.1
[1024, 1] | 7.6 | 17.4
[1024, 64] | 43.5 | 33.5
[1024, 1024] | 135.4 | 2782.3
[1024, 10000] | 7471.1 | 11874.0
[10000, 1] | 16.8 | 33.9
[10000, 64] | 118.7 | 173.2
[10000, 1024] | 7264.6 | 27824.7
[10000, 10000] | 100060.9 | 121499.0
16 threads: ----------------------------------
[1, 1] | 6.0 | 11.3
[1, 64] | 6.2 | 11.2
[1, 1024] | 6.9 | 14.2
[1, 10000] | 10.3 | 23.8
[64, 1] | 6.4 | 24.1
[64, 64] | 9.0 | 23.8
[64, 1024] | 54.1 | 188.5
[64, 10000] | 49.9 | 748.0
[1024, 1] | 7.6 | 23.4
[1024, 64] | 55.5 | 28.2
[1024, 1024] | 66.9 | 2773.9
[1024, 10000] | 6111.5 | 12833.7
[10000, 1] | 16.9 | 27.5
[10000, 64] | 59.5 | 73.7
[10000, 1024] | 6295.9 | 27062.0
[10000, 10000] | 71804.5 | 120365.8
32 threads: ----------------------------------
[1, 1] | 5.9 | 11.3
[1, 64] | 6.2 | 11.3
[1, 1024] | 6.7 | 14.2
[1, 10000] | 10.5 | 23.8
[64, 1] | 6.3 | 31.7
[64, 64] | 9.1 | 30.4
[64, 1024] | 72.0 | 190.4
[64, 10000] | 103.1 | 746.9
[1024, 1] | 7.6 | 28.4
[1024, 64] | 70.5 | 31.9
[1024, 1024] | 65.6 | 2804.6
[1024, 10000] | 6764.0 | 11871.4
[10000, 1] | 17.8 | 31.8
[10000, 64] | 110.3 | 56.0
[10000, 1024] | 6640.2 | 27592.2
[10000, 10000] | 73003.4 | 120083.2
Times are in microseconds (us).
上述结果表明，对于在多线程上运行的较大张量，简化为 bmm 的版本更好，而对于较小和/或单线程代码，另一个版本更好。
Compare 还提供了更改表格格式的函数
compare.trim_significant_figures()
compare.colorize()
compare.print()
6. 保存/加载基准测试结果#
Measurements（以及第 8 节中描述的 CallgrindStats）可以通过 pickle 模块进行序列化。这使得 A/B 测试变得容易，因为您可以从两个独立的环境中收集测量结果，将其 pickle 化，然后在一个环境中加载两者。Timer 甚至接受一个 env 构造函数参数，以便 A/B 测试无缝进行。
让我们假设，不是两个 Python 函数，而是 add/sum 和 bmm 方法存在于 PyTorch 的两个不同构建中。以下示例演示了如何对它们进行 A/B 测试。为简单起见，我们只使用形状的子集，并且只是通过 pickle 往返结果，而不是实际使用多个环境并将结果写入磁盘。
import pickle
ab_test_results = []
for env in ('environment A: mul/sum', 'environment B: bmm'):
for b, n in ((1, 1), (1024, 10000), (10000, 1)):
x = torch.ones((b, n))
dot_fn = (batched_dot_mul_sum if env == 'environment A: mul/sum' else batched_dot_bmm)
m = benchmark.Timer(
stmt='batched_dot(x, x)',
globals={'x': x, 'batched_dot': dot_fn},
num_threads=1,
label='Batched dot',
description=f'[{b}, {n}]',
env=env,
).blocked_autorange(min_run_time=1)
ab_test_results.append(pickle.dumps(m))
ab_results = [pickle.loads(i) for i in ab_test_results]
compare = benchmark.Compare(ab_results)
compare.trim_significant_figures()
compare.colorize()
compare.print()
输出#
[------------------------------------- Batched dot -------------------------------------]
| [1, 1] | [1024, 10000] | [10000, 1]
1 threads: ------------------------------------------------------------------------------
(environment A: mul/sum) batched_dot(x, x) | 7 | 36000 | 21
(environment B: bmm) batched_dot(x, x) | 14 | 40000 | 85
Times are in microseconds (us).
# And just to show that we can round trip all of the results from earlier:
round_tripped_results = pickle.loads(pickle.dumps(results))
assert(str(benchmark.Compare(results)) == str(benchmark.Compare(round_tripped_results)))
7. 使用 Fuzzed Parameters 生成输入#
正如我们在上一节中看到的，根据输入张量的不同，性能可能会有很大的差异。因此，在许多不同的输入上运行基准测试是一个好主意。但是，创建所有这些输入张量可能很繁琐，这就是 torch.utils.benchmark.Fuzzer 和相关类发挥作用的地方。让我们看看如何使用 Fuzzer 为基准测试创建一些测试用例。
from torch.utils.benchmark import Fuzzer, FuzzedParameter, FuzzedTensor, ParameterAlias
# Generates random tensors with 128 to 10000000 elements and sizes k0 and k1 chosen from a
# ``loguniform`` distribution in [1, 10000], 40% of which will be discontiguous on average.
example_fuzzer = Fuzzer(
parameters = [
FuzzedParameter('k0', minval=1, maxval=10000, distribution='loguniform'),
FuzzedParameter('k1', minval=1, maxval=10000, distribution='loguniform'),
],
tensors = [
FuzzedTensor('x', size=('k0', 'k1'), min_elements=128, max_elements=10000000, probability_contiguous=0.6)
],
seed=0,
)
results = []
for tensors, tensor_params, params in example_fuzzer.take(10):
# description is the column label
sub_label=f"{params['k0']:<6} x {params['k1']:<4} {'' if tensor_params['x']['is_contiguous'] else '(discontiguous)'}"
results.append(benchmark.Timer(
stmt='batched_dot_mul_sum(x, x)',
setup='from __main__ import batched_dot_mul_sum',
globals=tensors,
label='Batched dot',
sub_label=sub_label,
description='mul/sum',
).blocked_autorange(min_run_time=1))
results.append(benchmark.Timer(
stmt='batched_dot_bmm(x, x)',
setup='from __main__ import batched_dot_bmm',
globals=tensors,
label='Batched dot',
sub_label=sub_label,
description='bmm',
).blocked_autorange(min_run_time=1))
compare = benchmark.Compare(results)
compare.trim_significant_figures()
compare.print()
输出#
[--------------------- Batched dot ---------------------]
| mul/sum | bmm
1 threads: ----------------------------------------------
725 x 257 | 87 | 180
49 x 383 | 15 | 30
34 x 1468 | 30 | 118
187 x 5039 | 400 | 1200
2140 x 1296 (discontiguous) | 2000 | 41000
78 x 1598 | 74 | 310
519 x 763 | 190 | 1500
141 x 1082 | 87 | 500
78 x 5 (discontiguous) | 9 | 20
187 x 1 | 12 | 10
Times are in microseconds (us).
在定义自己的 fuzzers 方面有很多灵活性，这对于创建强大的基准测试输入集非常有用。但是为了让事情变得更简单，PyTorch 基准测试模块附带了一些内置的 fuzzers，用于常见的基准测试需求。让我们看看如何使用这些内置的 fuzzers 之一。
from torch.utils.benchmark.op_fuzzers import binary
results = []
for tensors, tensor_params, params in binary.BinaryOpFuzzer(seed=0).take(10):
sub_label=f"{params['k0']:<6} x {params['k1']:<4} {'' if tensor_params['x']['is_contiguous'] else '(discontiguous)'}"
results.append(benchmark.Timer(
stmt='batched_dot_mul_sum(x, x)',
setup='from __main__ import batched_dot_mul_sum',
globals=tensors,
label='Batched dot',
sub_label=sub_label,
description='mul/sum',
).blocked_autorange(min_run_time=1))
results.append(benchmark.Timer(
stmt='batched_dot_bmm(x, x)',
setup='from __main__ import batched_dot_bmm',
globals=tensors,
label='Batched dot',
sub_label=sub_label,
description='bmm',
).blocked_autorange(min_run_time=1))
compare = benchmark.Compare(results)
compare.trim_significant_figures()
compare.colorize(rowwise=True)
compare.print()
输出#
[----------------------- Batched dot ------------------------]
| mul/sum | bmm
1 threads: ---------------------------------------------------
64 x 473 (discontiguous) | 10000 | 40000
16384 x 12642115 (discontiguous) | 31 | 78
8192 x 892 | 4800 | 20400
512 x 64 (discontiguous) | 110000 | 400000
493 x 27 (discontiguous) | 1100 | 2440
118 x 32 (discontiguous) | 870 | 2030
16 x 495 (discontiguous) | 23600 | 24000
488 x 62374 | 90000 | 100000
240372 x 69 | 40000 | 16000
40156 x 32 (discontiguous) | 2670 | 5000
Times are in microseconds (us).
8. 使用 Callgrind 收集指令计数#
优化代码的挑战之一是墙钟时间的变异性和不透明性。存在许多不确定性来源，从自适应时钟速度到与其他进程的资源争用。此外，端到端时间无法提供关于时间花在哪里的见解，而这正是我们在优化代码时真正感兴趣的。
一种补充方法是收集指令计数。这些计数是一种代理度量，并不能捕获性能的所有方面（例如内存或 I/O 密集型任务），但是它们确实具有几个有用的特性。指令计数是可重现的，对环境变化不敏感，并提供了对程序在何处花费周期的细粒度洞察。
为了了解指令计数的实用性，让我们看看如何减少 batched_dot_mul_sum 的开销。显而易见的解决方案是将其移动到 C++，这样我们就可以避免多次在 Python 和 C++ 之间切换。
幸运的是，源代码几乎相同。我们在 C++ 中必须问的一个问题是，我们应该按值传递参数还是按引用传递参数。
batched_dot_src = """\
/* ---- Python ---- */
// def batched_dot_mul_sum(a, b):
// return a.mul(b).sum(-1)
torch::Tensor batched_dot_mul_sum_v0(
const torch::Tensor a,
const torch::Tensor b) {
return a.mul(b).sum(-1);
}
torch::Tensor batched_dot_mul_sum_v1(
const torch::Tensor& a,
const torch::Tensor& b) {
return a.mul(b).sum(-1);
}
"""
# PyTorch makes it easy to test our C++ implementations by providing a utility
# to JIT compile C++ source into Python extensions:
import os
from torch.utils import cpp_extension
cpp_lib = cpp_extension.load_inline(
name='cpp_lib',
cpp_sources=batched_dot_src,
extra_cflags=['-O3'],
extra_include_paths=[
# `load_inline` needs to know where to find ``pybind11`` headers.
os.path.join(os.getenv('CONDA_PREFIX'), 'include')
],
functions=['batched_dot_mul_sum_v0', 'batched_dot_mul_sum_v1']
)
# `load_inline` will create a shared object that is loaded into Python. When we collect
# instruction counts Timer will create a subprocess, so we need to re-import it. The
# import process is slightly more complicated for C extensions, but that's all we're
# doing here.
module_import_str = f"""\
# https://stackoverflow.com/questions/67631/how-to-import-a-module-given-the-full-path
import importlib.util
spec = importlib.util.spec_from_file_location("cpp_lib", {repr(cpp_lib.__file__)})
cpp_lib = importlib.util.module_from_spec(spec)
spec.loader.exec_module(cpp_lib)"""
import textwrap
def pretty_print(result):
"""Import machinery for ``cpp_lib.so`` can get repetitive to look at."""
print(repr(result).replace(textwrap.indent(module_import_str, " "), " import cpp_lib"))
t_baseline = benchmark.Timer(
stmt='batched_dot_mul_sum(x, x)',
setup='''\
from __main__ import batched_dot_mul_sum
x = torch.randn(2, 2)''')
t0 = benchmark.Timer(
stmt='cpp_lib.batched_dot_mul_sum_v0(x, x)',
setup=f'''\
{module_import_str}
x = torch.randn(2, 2)''')
t1 = benchmark.Timer(
stmt='cpp_lib.batched_dot_mul_sum_v1(x, x)',
setup=f'''\
{module_import_str}
x = torch.randn(2, 2)''')
# Moving to C++ did indeed reduce overhead, but it's hard to tell which
# calling convention is more efficient. v1 (call with references) seems to
# be a bit faster, but it's within measurement error.
pretty_print(t_baseline.blocked_autorange())
pretty_print(t0.blocked_autorange())
pretty_print(t1.blocked_autorange())
输出#
<torch.utils.benchmark.utils.common.Measurement object at 0x7fb16935d2e8>
batched_dot_mul_sum(x, x)
setup:
from __main__ import batched_dot_mul_sum
x = torch.randn(2, 2)
6.92 us
1 measurement, 100000 runs , 1 thread
<torch.utils.benchmark.utils.common.Measurement object at 0x7fb16935d2e8>
cpp_lib.batched_dot_mul_sum_v0(x, x)
setup:
import cpp_lib
x = torch.randn(2, 2)
5.29 us
1 measurement, 100000 runs , 1 thread
<torch.utils.benchmark.utils.common.Measurement object at 0x7fb16935d2e8>
cpp_lib.batched_dot_mul_sum_v1(x, x)
setup:
import cpp_lib
x = torch.randn(2, 2)
5.22 us
1 measurement, 100000 runs , 1 thread
# Let's use ``Callgrind`` to determine which is better.
stats_v0 = t0.collect_callgrind()
stats_v1 = t1.collect_callgrind()
pretty_print(stats_v0)
pretty_print(stats_v1)
# `.as_standardized` removes file names and some path prefixes, and makes
# it easier to read the function symbols.
stats_v0 = stats_v0.as_standardized()
stats_v1 = stats_v1.as_standardized()
# `.delta` diffs the instruction counts, and `.denoise` removes several
# functions in the Python interpreter that are known to have significant
# jitter.
delta = stats_v1.delta(stats_v0).denoise()
# `.transform` is a convenience API for transforming function names. It is
# useful for increasing cancelation when ``diff-ing`` instructions, as well as
# just generally improving readability.
replacements = (
("???:void pybind11", "pybind11"),
("batched_dot_mul_sum_v0", "batched_dot_mul_sum_v1"),
("at::Tensor, at::Tensor", "..."),
("at::Tensor const&, at::Tensor const&", "..."),
("auto torch::detail::wrap_pybind_function_impl_", "wrap_pybind_function_impl_"),
)
for before, after in replacements:
delta = delta.transform(lambda l: l.replace(before, after))
# We can use print options to control how much of the function to display.
torch.set_printoptions(linewidth=160)
# Once parsed, the instruction counts make clear that passing `a` and `b`
# by reference is more efficient as it skips some ``c10::TensorImpl`` bookkeeping
# for the intermediate Tensors, and is also works better with ``pybind11``. This
# is consistent with our noisy wall time observations.
print(delta)
<torch.utils.benchmark.utils.valgrind_wrapper.timer_interface.CallgrindStats object at 0x7fb0f06e7630>
cpp_lib.batched_dot_mul_sum_v0(x, x)
setup:
import cpp_lib
x = torch.randn(2, 2)
All Noisy symbols removed
Instructions: 2392671 2392671
Baseline: 4367 4367
100 runs per measurement, 1 thread
Warning: PyTorch was not built with debug symbols.
Source information may be limited. Rebuild with
REL_WITH_DEB_INFO=1 for more detailed results.
<torch.utils.benchmark.utils.valgrind_wrapper.timer_interface.CallgrindStats object at 0x7fb10400d208>
cpp_lib.batched_dot_mul_sum_v1(x, x)
setup:
import cpp_lib
x = torch.randn(2, 2)
All Noisy symbols removed
Instructions: 2378978 2378978
Baseline: 4367 4367
100 runs per measurement, 1 thread
Warning: PyTorch was not built with debug symbols.
Source information may be limited. Rebuild with
REL_WITH_DEB_INFO=1 for more detailed results.
<torch.utils.benchmark.utils.valgrind_wrapper.timer_interface.FunctionCounts object at 0x7fb1000ab358>
86 ???:0x000000000020d9e0
56 ???:0x000000000020db10
-1100 pybind11::cpp_function::initialize<wrap_pybind_function_impl_<at::Tensor ... r (&)(...), std::integer_sequence<unsigned long, 0ul, 1ul>)::{lambda(...)
-1600 ???:wrap_pybind_function_impl_<at::Tensor (&)(...), 0ul, 1ul>(at::Tensor (&)(...), std::integer_sequence<unsigned long, 0ul, 1ul>)::{lambda(...)
-5200 ???:c10::intrusive_ptr<c10::TensorImpl, c10::UndefinedTensorImpl>::reset_()
-5935 ???:0x000000000022c0e0
Total: -13693
了解更多#
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