[英]Global / local environment affects Haskell's Criterion benchmarks results
We're benchmarking some Haskell code in our company and we've just hit a very strange case. 我们正在对公司中的某些Haskell代码进行基准测试,而我们遇到了一个非常奇怪的案例。 Here is a code, which benchmarks the same thing 2 times.
这是一个代码,它对同一事物进行两次基准测试。 The former one uses an
Criterion.env
which is created for all the tests once, the later creates env for every test. 前者使用为所有测试创建一次的
Criterion.env
,后者使用每项测试创建env。 This is the only difference, however the one which creates env for each bench, runs 5 times faster. 这是唯一的区别,但是为每个工作台创建环境的运行速度提高了5倍。
Does anyone know what can cause it? 有谁知道会导致什么? Minimal example:
最小示例:
module Main where
import Prelude
import Control.Monad
import qualified Data.Vector.Storable.Mutable as Vector
import qualified Data.Vector.Storable as Vector
import Data.Vector.Storable (Vector)
import Criterion.Main
testf :: Int -> Vector Int -> IO (Vector Int)
testf !i !v = do
mv <- Vector.unsafeThaw v
let go j = do
x <- if j == 0 then return 0 else Vector.unsafeRead mv (j - 1)
Vector.unsafeWrite mv j (x+1)
when (j < i - 1) $ go (j + 1)
go 0
Vector.unsafeFreeze mv
mkVec :: Int -> IO (Vector Int)
mkVec !i = Vector.unsafeFreeze =<< Vector.new (i + 1)
main :: IO ()
main = do
defaultMain
[ bgroup "env per all runs"
$ (\(i :: Int) -> env (mkVec (10 ^ i))
$ \v -> bench ("10e" ++ show i)
$ nfIO (testf (10 ^ i) v)) <$> [7..8]
, bgroup "env per every run"
$ (\(i :: Int) -> bench ("10e" ++ show i)
$ perRunEnv (mkVec (10 ^ i))
$ (testf (10 ^ i))) <$> [7..8]
]
And results: 结果:
benchmarking env per all runs/10e7
time 17.34 ms (17.20 ms .. 17.41 ms)
0.999 R² (0.998 R² .. 1.000 R²)
mean 17.43 ms (17.34 ms .. 17.67 ms)
std dev 321.5 μs (142.1 μs .. 591.3 μs)
benchmarking env per all runs/10e8
time 173.5 ms (173.2 ms .. 173.8 ms)
1.000 R² (1.000 R² .. 1.000 R²)
mean 173.8 ms (173.6 ms .. 174.0 ms)
std dev 279.5 μs (194.9 μs .. 355.6 μs)
variance introduced by outliers: 12% (moderately inflated)
benchmarking env per every run/10e7
time 4.289 ms (1.807 ms .. 5.771 ms)
0.924 R² (0.696 R² .. 1.000 R²)
mean 8.903 ms (5.752 ms .. 14.20 ms)
std dev 5.029 ms (249.0 μs .. 6.244 ms)
variance introduced by outliers: 79% (severely inflated)
benchmarking env per every run/10e8
time 53.76 ms (30.23 ms .. 98.51 ms)
0.940 R² (0.920 R² .. 1.000 R²)
mean 102.9 ms (68.67 ms .. 127.1 ms)
std dev 36.55 ms (0.0 s .. 41.99 ms)
variance introduced by outliers: 73% (severely inflated)
As with your presumably-coworker's question, I can not reproduce this issue. 就像您的同事的问题一样,我无法重现此问题。 Note I am using GHC 8.2.2 and criterion 1.3.0.0
注意我正在使用GHC 8.2.2和标准1.3.0.0
benchmarking env per all runs/10e7
time 18.94 ms (18.71 ms .. 19.22 ms)
0.999 R² (0.998 R² .. 1.000 R²)
mean 19.59 ms (19.39 ms .. 19.99 ms)
std dev 618.3 μs (379.7 μs .. 952.8 μs)
benchmarking env per all runs/10e8
time 192.0 ms (189.5 ms .. 194.9 ms)
1.000 R² (0.999 R² .. 1.000 R²)
mean 191.8 ms (190.3 ms .. 193.1 ms)
std dev 1.778 ms (1.088 ms .. 2.457 ms)
variance introduced by outliers: 14% (moderately inflated)
benchmarking env per every run/10e7
time 18.97 ms (18.38 ms .. 19.62 ms)
0.999 R² (0.996 R² .. 1.000 R²)
mean 18.98 ms (18.83 ms .. 19.35 ms)
std dev 298.8 μs (25.39 μs .. 391.3 μs)
variance introduced by outliers: 14% (moderately inflated)
benchmarking env per every run/10e8
time 194.0 ms (182.0 ms .. 211.6 ms)
0.999 R² (0.997 R² .. 1.000 R²)
mean 192.0 ms (189.0 ms .. 193.9 ms)
std dev 2.850 ms (0.0 s .. 3.261 ms)
variance introduced by outliers: 19% (moderately inflated)
./p 18.32s user 1.16s system 99% cpu 19.531 total
% ghc-pkg list criterion
...
criterion-1.3.0.0
I notice my version of criterion was uploaded after the bug @jberryman pointed to was fixed, so perhaps this is the difference. 我注意到我的标准版本是在修正了@jberryman所指出的错误之后上传的,所以也许是不同的。
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