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PyTorch 基准测试¶
创建于: 2020 年 12 月 02 日 | 最后更新: 2023 年 05 月 09 日 | 最后验证: 2024 年 11 月 05 日
本教程集提供了一个快速入门指南，用于使用 PyTorch benchmark 模块衡量和比较代码性能。
介绍¶
基准测试是编写代码的重要步骤。它有助于我们验证代码是否满足性能预期，比较解决同一问题的不同方法，并防止性能退步。
基准测试 PyTorch 代码有许多选项，包括 Python 内置的 timeit 模块。然而，基准测试 PyTorch 代码有许多容易被忽略的注意事项，例如管理线程数和同步 CUDA 设备。此外，生成用于基准测试的张量输入可能相当繁琐。
本教程集演示了如何使用 PyTorch benchmark 模块来避免常见错误，同时使得比较不同代码的性能、生成用于基准测试的输入等更加容易。
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¶
截至本文撰写之时，torch.dot 不支持批处理模式，因此我们将比较两种使用现有 torch 算子实现它的方法：一种方法使用 mul 和 sum 的组合，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。为了比较 timeit 和 torch.utils.benchmark 的默认设置，这里我们保持基准测试代码简单。
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 模块的设计旨在让熟悉 timeit 模块的人感到熟悉。然而，它的默认设置使得它对于基准测试 PyTorch 代码来说更容易且更安全。让我们先比较一下与上面相同的基本 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，但有一些重要的差异。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。
另一个重要的区别，也是结果差异的原因是 PyTorch 基准测试模块默认在单个线程中运行。我们可以使用 num_threads 参数改变线程数。
torch.utils.benchmark.Timer 接受几个额外的参数，包括：label, sub_label, description 和 env，它们会改变返回的测量对象的 __repr__ 并用于结果的分组（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 可以获得与 timeit 模块相似的结果。更重要的是，哪个版本更快取决于我们使用多少个线程运行代码。这就是为什么使用代表实际用例的线程设置进行基准测试很重要。另一件需要记住的重要事情是，在 GPU 上进行基准测试时要同步 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 模块运行 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 调用了 cuBLAS，它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热身运行很重要，幸运的是，PyTorch 的 benchmark 模块会处理这个问题。
timeit 和 benchmark 模块之间结果的差异是因为 timeit 模块没有同步 CUDA，因此只计时了启动内核的时间。PyTorch 的 benchmark 模块为我们进行了同步。
4. 使用 Blocked Autorange 进行基准测试¶
timeit.Timer.autorange 进行至少 0.2 秒的连续测量，而 torch.utils.benchmark.blocked_autorange 进行多次测量，其总时间至少为 0.2 秒（可以通过 min_run_time 参数更改），但受限于测量开销占总体测量的一小部分。这通过首先增加每次循环的运行次数，直到运行时长远大于测量开销（这也用作热身），然后进行测量直到达到目标时间来实现。这具有以下有用的属性：它浪费更少的数据，并且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 measurements 对象中的各个统计数据。
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，我们一直在针对单个输入比较我们的两个批处理点乘版本。实际上，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显示许多测量的结果。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 来看看我们的函数在不同输入大小和线程数下的性能。
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).
上面的结果表明，归结为 bmm 的版本对于在多个线程上运行的较大张量更好，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，因为你可以从两个独立的环境收集测量结果，将其 pickle 序列化，然后在单个环境中加载两者。Timer 甚至接受 env 构造函数参数，以便此类 A/B 测试无缝工作。
让我们想象一下，加法/求和和 bmm 方法不是两个 Python 函数，而是在 PyTorch 的两个不同构建版本中。下面的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 来回传输结果，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那样，根据输入张量的不同，性能可能会有很大的差异。因此，对许多不同的输入运行基准测试是一个好主意。然而，创建所有这些输入张量可能很繁琐，这时 torch.utils.benchmark.Fuzzer 及相关类就派上用场了。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).
在定义你自己的 fuzzers 方面有很多灵活性，这对于创建一组强大的输入进行基准测试非常有用。但为了让事情变得更简单，PyTorch benchmark 模块自带了一些用于常见基准测试需求的内置 fuzzers。让我们看看如何使用这些内置 fuzzers 中的一个。
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实时时间的变异性和不透明性。有许多非确定性来源，从自适应时钟速度到与其他进程的资源争夺。此外，端到端时间无法洞察时间花在哪里，而这正是我们在优化代码时真正感兴趣的。
一种互补的方法是同时收集指令计数。这些计数是一种代理指标，不能捕捉性能的所有方面（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属性。指令计数是可重现的，对环境变化不敏感，并提供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效用，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至 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。
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
