我需要尽可能快地生成整数0、1、2、...、n - 1的所有排列，并将结果作为形状为(factorial(n), n)的NumPy数组，或者迭代这样的数组的大部分以节省内存。
NumPy中是否有一些内置函数可以实现这一点？或者一些功能的组合。
使用itertools.permutations(...)太慢了，我需要一个更快的方法。
这里有一个NumPy解决方案，它通过修改大小m-1的排列来构建大小m的排列(请参阅下面的更多解释(：
def permutations(n):
a = np.zeros((np.math.factorial(n), n), np.uint8)
f = 1
for m in range(2, n+1):
b = a[:f, n-m+1:] # the block of permutations of range(m-1)
for i in range(1, m):
a[i*f:(i+1)*f, n-m] = i
a[i*f:(i+1)*f, n-m+1:] = b + (b >= i)
b += 1
f *= m
return a
演示：
>>> permutations(3)
array([[0, 1, 2],
[0, 2, 1],
[1, 0, 2],
[1, 2, 0],
[2, 0, 1],
[2, 1, 0]], dtype=uint8)
对于n=10，itertools解决方案需要5.5秒，而这个NumPy解决方案需要0.2秒。
如何进行：它从一个目标大小的零数组开始，该数组已经包含右上角range(1)的排列(数组的其他部分I"点出"(：
[[. . 0]
[. . .]
[. . .]
[. . .]
[. . .]
[. . .]]
然后将其转化为range(2):的排列
[[. 0 1]
[. 1 0]
[. . .]
[. . .]
[. . .]
[. . .]]
然后引入range(3):的排列
[[0 1 2]
[0 2 1]
[1 0 2]
[1 2 0]
[2 0 1]
[2 1 0]]
它通过填充下一个左列并向下复制/修改前一个排列块来实现这一点。
更新：更快的版本
由于避免了不必要的计算，这个解决方案比我原来的答案快了大约5倍。这种方法通过从一个角落扩展来构建阵列，使用了与superior rain的答案中解释的相同的基本思想，但速度要快得多，因为它避免了不必要的工作。
def faster_permutations(n):
# empty() is fast because it does not initialize the values of the array
# order='F' uses Fortran ordering, which makes accessing elements in the same column fast
perms = np.empty((np.math.factorial(n), n), dtype=np.uint8, order='F')
perms[0, 0] = 0
rows_to_copy = 1
for i in range(1, n):
perms[:rows_to_copy, i] = i
for j in range(1, i + 1):
start_row = rows_to_copy * j
end_row = rows_to_copy * (j + 1)
splitter = i - j
perms[start_row: end_row, splitter] = i
perms[start_row: end_row, :splitter] = perms[:rows_to_copy, :splitter] # left side
perms[start_row: end_row, splitter + 1:i + 1] = perms[:rows_to_copy, splitter:i] # right side
rows_to_copy *= i + 1
return perms
我的n=11:机器上的计时
faster_permutations(): 0.12 seconds
permutations() [superb rain's approach]: 1.44 seconds
permutations() with memory order optimization: 0.62 seconds
原始答案：
基于极好的rain的答案，这是一个具有更高效内存访问模式的更快版本：
def fast_permutations(n):
a = np.zeros((n, np.math.factorial(n)), np.uint8)
f = 1
for m in range(2, n + 1):
b = a[n - m + 1:, :f] # the block of permutations of range(m-1)
for i in range(1, m):
a[n - m, i * f:(i + 1) * f] = i
a[n - m + 1:, i * f:(i + 1) * f] = b + (b >= i)
b += 1
f *= m
return a.T
这基本上是极好的雨版本的转调。它的效率更高，因为访问的内存位置离得更近。
在我的机器上，它的速度大约是原始版本的2倍(0.05秒vsn=10的0.12秒(。
由于我没有找到一个足够好/足够快的解决方案，我决定使用Numba JIT/AOT代码编译器/优化器从头开始实现整个排列算法。
我的下一个基于numba的解决方案是，对于足够大的n，25x-50x的速度是使用itertools.permutations(...)执行相同任务的速度的13倍。请参阅代码后的计时。
如果一次迭代1个排列，我的代码只比itertools.permutations(...)快1.25x，但根据最初的问题，我需要所有排列的整个数组，或者至少在大块上迭代。
我已经实现了在numba模式中同时使用numba和无numba模式以及JIT和AOT变体的可能性。此外，可以选择是一次迭代一个排列(iter_ = True, iter_batches = False(，还是在快得多的时间迭代一批排列(iter_ = True, iter_batches = True(，或者在不迭代的情况下返回所有排列的整个阵列(iter_ = False(。此外，还可以调整批量大小，例如通过batch_size = 1000。
核心内部函数是next_batch(...)，它实际上实现了在给定前一个排列的情况下生成下一排列的整个算法。它是唯一一个通过numba实现的JITed/AOTed函数，其余的都是helper纯Python包装器。
我的时间安排不太准确，因为我的笔记本电脑的CPU在过热时会在随机时间点减慢2.2x次(这种情况经常发生(。
今天(2022.02.23(还增加了超级雨解决方案的时间安排，@DanielGieger提出了改进建议。它似乎和我的Numba解决方案的时间差不多(如果不改进的话(，如果使用@DanielGieger的改进，它的速度大约是Numba的1.8倍。
在线试用！
# Needs: python -m pip install numba numpy timerit
def permutations(
n, *, iter_ = True, numba_ = True, numba_aot = False,
batch_size = 1000, iter_batches = False, state = {},
):
key = (bool(numba_), bool(numba_aot))
if key in state:
return state[key](int(n), bool(iter_), int(batch_size), bool(iter_batches))
def prepare(numba_, numba_aot):
import numpy as np
def next_batch(a, r):
c, n = r.shape[0], r.shape[1]
for ic in range(c):
r[ic] = a
a = r[ic]
for i in range(n - 2, -1, -1):
if a[i] < a[i + 1]:
break
else:
assert False # Already last permutation
for j in range(n - 1, i, -1):
if a[i] < a[j]:
break
a[i], a[j] = a[j], a[i]
for k in range(1, (n - i + 1) >> 1):
a[i + k], a[n - k] = a[n - k], a[i + k]
def factorial(n):
res = 1
for i in range(2, n + 1):
res *= i
return res
def permutations_iter(nxb, n, batch_size, iter_batches):
a = np.arange(n, dtype = np.uint8)
if iter_batches:
yield a[None, :]
else:
yield a
if n <= 1:
return
total = factorial(n)
for i in range(1, total, batch_size):
batch = np.empty((min(batch_size, total - i), n), dtype = np.uint8)
nxb(a, batch)
if iter_batches:
yield batch
else:
yield from iter(batch)
a = batch[-1]
def permutations_arr(nxb, n, batch_size):
total = factorial(n)
res = np.empty((total, n), dtype = np.uint8)
res[0] = np.arange(n, dtype = np.uint8)
for i in range(1, total, batch_size):
nxb(res[i - 1], res[i : i + min(batch_size, total - i)])
return res
if not numba_:
return lambda n, it, bs, ib: permutations_iter(next_batch, n, bs, ib) if it else permutations_arr(next_batch, n, bs)
else:
if not numba_aot:
import numba
nxb = numba.njit('void(u1[:], u1[:, :])', cache = True)(next_batch)
else:
import numba, numba.pycc
cc = numba.pycc.CC('permutations_numba')
cc.export('next_batch', 'void(u1[:], u1[:, :])')(next_batch)
cc.compile()
from permutations_numba import next_batch as nxb
return lambda n, it, bs, ib: permutations_iter(nxb, n, bs, ib) if it else permutations_arr(nxb, n, bs)
state[key] = prepare(numba_, numba_aot)
return state[key](int(n), bool(iter_), int(batch_size), bool(iter_batches))
def test():
import numpy as np, itertools
from timerit import Timerit
Timerit._default_asciimode = True
# Heat-up / pre-compile
permutations(2, numba_ = False)
permutations(2, numba_ = True)
for n in range(12):
num = 99 if n <= 7 else 15 if n <= 8 else 3 if n <= 9 else 1
print('-' * 60 + f'nn = {str(n).rjust(2)}')
print(f'itertools : ', end = '', flush = True)
for t in Timerit(num = num, verbose = 1):
with t:
ref = np.array(list(itertools.permutations(range(n))), dtype = np.uint8)
def superbrain(n):
a = np.zeros((n, np.math.factorial(n)), np.uint8).T
f = 1
for m in range(2, n+1):
b = a[:f, n-m+1:] # the block of permutations of range(m-1)
for i in range(1, m):
a[i*f:(i+1)*f, n-m] = i
a[i*f:(i+1)*f, n-m+1:] = b + (b >= i)
b += 1
f *= m
return a
print(f'superbrain : ', end = '', flush = True)
for t in Timerit(num = num, verbose = 1):
with t:
cur = superbrain(n)
assert np.array_equal(ref, cur)
if n <= 9:
print(f'python_array : ', end = '', flush = True)
for t in Timerit(num = num, verbose = 1):
with t:
curpa = permutations(n, iter_ = False, numba_ = False)
assert np.array_equal(ref, curpa)
for batch_size in [10, 100, 1000, 10000]:
print(f'batch_size = {str(batch_size).rjust(5)}')
print(f'numba_iter : ', end = '', flush = True)
for t in Timerit(num = num, verbose = 1):
with t:
curi = np.array(list(permutations(n, iter_ = True, numba_ = True, batch_size = batch_size)))
assert np.array_equal(ref, curi)
print(f'numba_iter_batches : ', end = '', flush = True)
for t in Timerit(num = num, verbose = 1):
with t:
curib = np.concatenate(list(permutations(n, iter_ = True, numba_ = True, batch_size = batch_size, iter_batches = True)))
assert np.array_equal(ref, curib)
print(f'numba_array : ', end = '', flush = True)
for t in Timerit(num = num, verbose = 1):
with t:
cura = permutations(n, iter_ = False, numba_ = True, batch_size = batch_size)
assert np.array_equal(ref, cura)
if __name__ == '__main__':
test()
输出(定时(：
------------------------------------------------------------
n = 0
itertools : Timed best=8.210 us, mean=8.335 +- 0.4 us
python_array : Timed best=14.881 us, mean=15.457 +- 0.5 us
batch_size = 10
numba_iter : Timed best=15.908 us, mean=16.126 +- 0.3 us
numba_iter_batches : Timed best=17.447 us, mean=17.929 +- 0.3 us
numba_array : Timed best=15.394 us, mean=15.519 +- 0.3 us
batch_size = 100
numba_iter : Timed best=15.908 us, mean=16.250 +- 0.3 us
numba_iter_batches : Timed best=17.447 us, mean=18.038 +- 0.2 us
numba_array : Timed best=15.394 us, mean=15.519 +- 0.3 us
batch_size = 1000
numba_iter : Timed best=15.908 us, mean=16.328 +- 0.3 us
numba_iter_batches : Timed best=17.960 us, mean=18.069 +- 0.2 us
numba_array : Timed best=15.394 us, mean=15.441 +- 0.1 us
batch_size = 10000
numba_iter : Timed best=15.908 us, mean=16.328 +- 0.2 us
numba_iter_batches : Timed best=17.448 us, mean=17.976 +- 0.2 us
numba_array : Timed best=14.881 us, mean=15.410 +- 0.3 us
------------------------------------------------------------
n = 1
itertools : Timed best=7.697 us, mean=7.790 +- 0.3 us
python_array : Timed best=14.882 us, mean=15.488 +- 0.3 us
batch_size = 10
numba_iter : Timed best=15.908 us, mean=16.064 +- 0.3 us
numba_iter_batches : Timed best=17.960 us, mean=18.318 +- 0.3 us
numba_array : Timed best=14.881 us, mean=15.348 +- 0.3 us
batch_size = 100
numba_iter : Timed best=15.908 us, mean=16.203 +- 0.3 us
numba_iter_batches : Timed best=17.960 us, mean=18.054 +- 0.2 us
numba_array : Timed best=15.394 us, mean=15.472 +- 0.2 us
batch_size = 1000
numba_iter : Timed best=15.908 us, mean=16.421 +- 0.1 us
numba_iter_batches : Timed best=17.960 us, mean=18.147 +- 0.3 us
numba_array : Timed best=14.882 us, mean=15.379 +- 0.2 us
batch_size = 10000
numba_iter : Timed best=15.908 us, mean=16.095 +- 0.2 us
numba_iter_batches : Timed best=17.960 us, mean=18.132 +- 0.3 us
numba_array : Timed best=14.881 us, mean=15.395 +- 0.3 us
------------------------------------------------------------
n = 2
itertools : Timed best=8.723 us, mean=8.786 +- 0.2 us
python_array : Timed best=29.250 us, mean=29.670 +- 0.4 us
batch_size = 10
numba_iter : Timed best=34.381 us, mean=35.035 +- 0.7 us
numba_iter_batches : Timed best=30.276 us, mean=30.790 +- 0.4 us
numba_array : Timed best=22.579 us, mean=22.672 +- 0.2 us
batch_size = 100
numba_iter : Timed best=34.381 us, mean=34.584 +- 0.3 us
numba_iter_batches : Timed best=30.277 us, mean=30.836 +- 0.2 us
numba_array : Timed best=22.066 us, mean=22.595 +- 0.2 us
batch_size = 1000
numba_iter : Timed best=34.381 us, mean=34.739 +- 0.4 us
numba_iter_batches : Timed best=30.277 us, mean=30.851 +- 0.3 us
numba_array : Timed best=22.579 us, mean=22.626 +- 0.1 us
batch_size = 10000
numba_iter : Timed best=34.381 us, mean=34.786 +- 0.4 us
numba_iter_batches : Timed best=30.276 us, mean=30.650 +- 0.3 us
numba_array : Timed best=22.066 us, mean=22.641 +- 0.3 us
------------------------------------------------------------
n = 3
itertools : Timed best=12.829 us, mean=13.093 +- 0.3 us
python_array : Timed best=62.606 us, mean=63.461 +- 0.6 us
batch_size = 10
numba_iter : Timed best=39.513 us, mean=40.120 +- 0.4 us
numba_iter_batches : Timed best=31.302 us, mean=31.661 +- 0.2 us
numba_array : Timed best=22.579 us, mean=23.077 +- 0.3 us
batch_size = 100
numba_iter : Timed best=39.513 us, mean=40.042 +- 0.2 us
numba_iter_batches : Timed best=31.302 us, mean=31.629 +- 0.3 us
numba_array : Timed best=22.579 us, mean=23.154 +- 0.2 us
batch_size = 1000
numba_iter : Timed best=39.513 us, mean=39.840 +- 0.4 us
numba_iter_batches : Timed best=31.302 us, mean=31.629 +- 0.4 us
numba_array : Timed best=22.579 us, mean=23.170 +- 0.2 us
batch_size = 10000
numba_iter : Timed best=39.513 us, mean=40.120 +- 0.5 us
numba_iter_batches : Timed best=30.789 us, mean=31.412 +- 0.3 us
numba_array : Timed best=23.092 us, mean=23.232 +- 0.3 us
------------------------------------------------------------
n = 4
itertools : Timed best=34.381 us, mean=34.911 +- 0.4 us
python_array : Timed best=207.830 us, mean=209.152 +- 1.0 us
batch_size = 10
numba_iter : Timed best=82.619 us, mean=83.054 +- 0.7 us
numba_iter_batches : Timed best=44.645 us, mean=44.754 +- 0.2 us
numba_array : Timed best=31.302 us, mean=31.458 +- 0.2 us
batch_size = 100
numba_iter : Timed best=63.632 us, mean=64.036 +- 0.4 us
numba_iter_batches : Timed best=32.329 us, mean=32.889 +- 0.2 us
numba_array : Timed best=24.118 us, mean=24.600 +- 0.3 us
batch_size = 1000
numba_iter : Timed best=63.632 us, mean=64.083 +- 0.5 us
numba_iter_batches : Timed best=32.329 us, mean=32.904 +- 0.3 us
numba_array : Timed best=24.118 us, mean=24.569 +- 0.3 us
batch_size = 10000
numba_iter : Timed best=63.119 us, mean=63.927 +- 0.4 us
numba_iter_batches : Timed best=32.329 us, mean=32.889 +- 0.5 us
numba_array : Timed best=24.118 us, mean=24.461 +- 0.3 us
------------------------------------------------------------
n = 5
itertools : Timed best=156.001 us, mean=166.311 +- 20.5 us
python_array : Timed best=0.999 ms, mean=1.002 +- 0.0 ms
batch_size = 10
numba_iter : Timed best=293.528 us, mean=294.461 +- 0.8 us
numba_iter_batches : Timed best=102.632 us, mean=103.254 +- 0.4 us
numba_array : Timed best=64.145 us, mean=64.985 +- 0.5 us
batch_size = 100
numba_iter : Timed best=198.080 us, mean=199.107 +- 0.8 us
numba_iter_batches : Timed best=44.132 us, mean=44.894 +- 0.4 us
numba_array : Timed best=33.355 us, mean=33.884 +- 0.3 us
batch_size = 1000
numba_iter : Timed best=186.791 us, mean=187.522 +- 0.4 us
numba_iter_batches : Timed best=37.973 us, mean=38.471 +- 0.3 us
numba_array : Timed best=29.763 us, mean=30.183 +- 0.3 us
batch_size = 10000
numba_iter : Timed best=186.790 us, mean=187.646 +- 0.7 us
numba_iter_batches : Timed best=37.974 us, mean=38.534 +- 0.3 us
numba_array : Timed best=29.763 us, mean=30.245 +- 0.3 us
------------------------------------------------------------
n = 6
itertools : Timed best=0.991 ms, mean=1.007 +- 0.0 ms
python_array : Timed best=5.873 ms, mean=6.012 +- 0.0 ms
batch_size = 10
numba_iter : Timed best=1.668 ms, mean=1.673 +- 0.0 ms
numba_iter_batches : Timed best=503.411 us, mean=506.506 +- 1.2 us
numba_array : Timed best=293.015 us, mean=296.047 +- 1.2 us
batch_size = 100
numba_iter : Timed best=1.036 ms, mean=1.145 +- 0.3 ms
numba_iter_batches : Timed best=120.593 us, mean=132.878 +- 23.0 us
numba_array : Timed best=93.908 us, mean=97.438 +- 2.4 us
batch_size = 1000
numba_iter : Timed best=962.178 us, mean=976.624 +- 23.9 us
numba_iter_batches : Timed best=78.001 us, mean=82.992 +- 7.7 us
numba_array : Timed best=68.250 us, mean=69.852 +- 4.3 us
batch_size = 10000
numba_iter : Timed best=963.717 us, mean=977.044 +- 27.3 us
numba_iter_batches : Timed best=77.487 us, mean=80.084 +- 7.5 us
numba_array : Timed best=68.250 us, mean=69.634 +- 4.4 us
------------------------------------------------------------
n = 7
itertools : Timed best=8.502 ms, mean=8.579 +- 0.0 ms
python_array : Timed best=41.690 ms, mean=42.358 +- 0.8 ms
batch_size = 10
numba_iter : Timed best=11.523 ms, mean=11.646 +- 0.2 ms
numba_iter_batches : Timed best=3.407 ms, mean=3.497 +- 0.1 ms
numba_array : Timed best=1.944 ms, mean=1.975 +- 0.0 ms
batch_size = 100
numba_iter : Timed best=7.050 ms, mean=7.397 +- 0.3 ms
numba_iter_batches : Timed best=659.925 us, mean=668.198 +- 5.9 us
numba_array : Timed best=503.411 us, mean=506.086 +- 3.3 us
batch_size = 1000
numba_iter : Timed best=6.576 ms, mean=6.630 +- 0.0 ms
numba_iter_batches : Timed best=382.305 us, mean=389.707 +- 4.4 us
numba_array : Timed best=354.081 us, mean=360.364 +- 4.3 us
batch_size = 10000
numba_iter : Timed best=6.463 ms, mean=6.504 +- 0.0 ms
numba_iter_batches : Timed best=349.976 us, mean=352.091 +- 1.5 us
numba_array : Timed best=330.989 us, mean=337.194 +- 1.8 us
------------------------------------------------------------
n = 8
itertools : Timed best=71.003 ms, mean=71.824 +- 0.5 ms
python_array : Timed best=331.176 ms, mean=339.746 +- 7.3 ms
batch_size = 10
numba_iter : Timed best=99.929 ms, mean=101.098 +- 1.3 ms
numba_iter_batches : Timed best=27.489 ms, mean=27.905 +- 0.3 ms
numba_array : Timed best=15.370 ms, mean=15.560 +- 0.1 ms
batch_size = 100
numba_iter : Timed best=62.168 ms, mean=62.765 +- 0.7 ms
numba_iter_batches : Timed best=5.083 ms, mean=5.119 +- 0.0 ms
numba_array : Timed best=3.824 ms, mean=3.842 +- 0.0 ms
batch_size = 1000
numba_iter : Timed best=57.706 ms, mean=57.935 +- 0.2 ms
numba_iter_batches : Timed best=2.824 ms, mean=2.832 +- 0.0 ms
numba_array : Timed best=2.656 ms, mean=2.670 +- 0.0 ms
batch_size = 10000
numba_iter : Timed best=57.457 ms, mean=60.128 +- 2.1 ms
numba_iter_batches : Timed best=2.615 ms, mean=2.635 +- 0.0 ms
numba_array : Timed best=2.550 ms, mean=2.565 +- 0.0 ms
------------------------------------------------------------
n = 9
itertools : Timed best=724.017 ms, mean=724.017 +- 0.0 ms
python_array : Timed best=3.071 s, mean=3.071 +- 0.0 s
batch_size = 10
numba_iter : Timed best=950.892 ms, mean=950.892 +- 0.0 ms
numba_iter_batches : Timed best=261.376 ms, mean=261.376 +- 0.0 ms
numba_array : Timed best=145.207 ms, mean=145.207 +- 0.0 ms
batch_size = 100
numba_iter : Timed best=584.761 ms, mean=584.761 +- 0.0 ms
numba_iter_batches : Timed best=50.632 ms, mean=50.632 +- 0.0 ms
numba_array : Timed best=39.945 ms, mean=39.945 +- 0.0 ms
batch_size = 1000
numba_iter : Timed best=535.190 ms, mean=535.190 +- 0.0 ms
numba_iter_batches : Timed best=29.557 ms, mean=29.557 +- 0.0 ms
numba_array : Timed best=26.541 ms, mean=26.541 +- 0.0 ms
batch_size = 10000
numba_iter : Timed best=533.592 ms, mean=533.592 +- 0.0 ms
numba_iter_batches : Timed best=27.507 ms, mean=27.507 +- 0.0 ms
numba_array : Timed best=25.115 ms, mean=25.115 +- 0.0 ms
------------------------------------------------------------
n = 10
itertools : Timed best=15.483 s, mean=15.483 +- 0.0 s
batch_size = 10
numba_iter : Timed best=24.163 s, mean=24.163 +- 0.0 s
numba_iter_batches : Timed best=6.039 s, mean=6.039 +- 0.0 s
numba_array : Timed best=3.246 s, mean=3.246 +- 0.0 s
batch_size = 100
numba_iter : Timed best=13.891 s, mean=13.891 +- 0.0 s
numba_iter_batches : Timed best=1.136 s, mean=1.136 +- 0.0 s
numba_array : Timed best=890.228 ms, mean=890.228 +- 0.0 ms
batch_size = 1000
numba_iter : Timed best=12.768 s, mean=12.768 +- 0.0 s
numba_iter_batches : Timed best=693.685 ms, mean=693.685 +- 0.0 ms
numba_array : Timed best=658.007 ms, mean=658.007 +- 0.0 ms
batch_size = 10000
numba_iter : Timed best=11.175 s, mean=11.175 +- 0.0 s
numba_iter_batches : Timed best=278.304 ms, mean=278.304 +- 0.0 ms
numba_array : Timed best=251.208 ms, mean=251.208 +- 0.0 ms
------------------------------------------------------------
n = 11
itertools : Timed best=95.118 s, mean=95.118 +- 0.0 s
batch_size = 10
numba_iter : Timed best=124.414 s, mean=124.414 +- 0.0 s
numba_iter_batches : Timed best=75.427 s, mean=75.427 +- 0.0 s
numba_array : Timed best=28.079 s, mean=28.079 +- 0.0 s
batch_size = 100
numba_iter : Timed best=70.749 s, mean=70.749 +- 0.0 s
numba_iter_batches : Timed best=6.084 s, mean=6.084 +- 0.0 s
numba_array : Timed best=4.357 s, mean=4.357 +- 0.0 s
batch_size = 1000
numba_iter : Timed best=67.576 s, mean=67.576 +- 0.0 s
numba_iter_batches : Timed best=8.572 s, mean=8.572 +- 0.0 s
numba_array : Timed best=6.915 s, mean=6.915 +- 0.0 s
batch_size = 10000
numba_iter : Timed best=123.208 s, mean=123.208 +- 0.0 s
numba_iter_batches : Timed best=3.348 s, mean=3.348 +- 0.0 s
numba_array : Timed best=2.789 s, mean=2.789 +- 0.0 s