python引入jit_python – 使用numba.jit编译一系列条件需要很长时间

如果我尝试使用numba的jit-compiler编译包含一系列条件的函数,则需要很长时间.该程序看起来基本上像

from numba import jit

import numpy as np

@jit(nopython=True)

def foo(a, b):

valid = [

(a - 1 >= 0) and (b - 1 >= 0),

(a - 1 >= 0) and (b - 1 >= 0),

(a - 1 >= 0) and (b - 1 >= 0),

(a - 1 >= 0) and (b - 1 >= 0),

(a - 1 >= 0) and (b - 1 >= 0),

(a - 1 >= 0) and (b - 1 >= 0),

(a - 1 >= 0) and (b - 1 >= 0),

(a - 1 >= 0) and (b - 1 >= 0),

(a - 1 >= 0) and (b - 1 >= 0),

(a - 1 >= 0) and (b - 1 >= 0),

(a - 1 >= 0) and (b - 1 >= 0),

(a - 1 >= 0) and (b - 1 >= 0),

(a - 1 >= 0) and (b - 1 >= 0),

(a - 1 >= 0) and (b - 1 >= 0),

(a - 1 >= 0) and (b - 1 >= 0),

(a - 1 >= 0) and (b - 1 >= 0),

(a - 1 >= 0) and (b - 1 >= 0),

(a - 1 >= 0) and (b - 1 >= 0),

(a - 1 >= 0) and (b - 1 >= 0),

(a - 1 >= 0) and (b - 1 >= 0),

(a - 1 >= 0) and (b - 1 >= 0),

(a - 1 >= 0) and (b - 1 >= 0),

(a - 1 >= 0) and (b - 1 >= 0)

]

foo(1, 1)

我已经排除了所有不会显着改变编译时间的东西.如果我使用超过20个元素,就会出现问题.

| elements | time |

-------------------

| 21 | 2.7s |

| 22 | 5.1s |

| 23 | 10s |

| ... | ... |

-------------------

尽管如此,该功能运作良好.有人知道,为什么需要这么长时间,用numba编译这样的函数？使用整数或浮点数组合以类似方式创建数组不会产生任何问题.

解决方法:

>你可能想在numba issue tracker上报告这一点,感觉编译器中的某些东西出错,因为它的扩展性很差.

>您也可以考虑是否真的需要大量这样的数组语句,如果问题可以更明确地重构.例如.而不是布尔数组,有效是一个被称为需要的函数吗？

>尽管如此,当前版本的numba中的解决方法正在展开这些条件.

对于你的例子：

# "codegen"

for i in range(23):

print(f' valid[{i}] = (a - 1 >= 0) and (b - 1 >= 0)')

@jit(nopython=True)

def foo(a, b):

valid = np.empty(23, dtype=np.bool_)

valid[0] = (a - 1 >= 0) and (b - 1 >= 0)

valid[1] = (a - 1 >= 0) and (b - 1 >= 0)

valid[2] = (a - 1 >= 0) and (b - 1 >= 0)

valid[3] = (a - 1 >= 0) and (b - 1 >= 0)

valid[4] = (a - 1 >= 0) and (b - 1 >= 0)

valid[5] = (a - 1 >= 0) and (b - 1 >= 0)

valid[6] = (a - 1 >= 0) and (b - 1 >= 0)

valid[7] = (a - 1 >= 0) and (b - 1 >= 0)

valid[8] = (a - 1 >= 0) and (b - 1 >= 0)

valid[9] = (a - 1 >= 0) and (b - 1 >= 0)

valid[10] = (a - 1 >= 0) and (b - 1 >= 0)

valid[11] = (a - 1 >= 0) and (b - 1 >= 0)

valid[12] = (a - 1 >= 0) and (b - 1 >= 0)

valid[13] = (a - 1 >= 0) and (b - 1 >= 0)

valid[14] = (a - 1 >= 0) and (b - 1 >= 0)

valid[15] = (a - 1 >= 0) and (b - 1 >= 0)

valid[16] = (a - 1 >= 0) and (b - 1 >= 0)

valid[17] = (a - 1 >= 0) and (b - 1 >= 0)

valid[18] = (a - 1 >= 0) and (b - 1 >= 0)

valid[19] = (a - 1 >= 0) and (b - 1 >= 0)

valid[20] = (a - 1 >= 0) and (b - 1 >= 0)

valid[21] = (a - 1 >= 0) and (b - 1 >= 0)

valid[22] = (a - 1 >= 0) and (b - 1 >= 0)

%time foo(1,1)

Wall time: 274 ms

标签：python,time,jit,condition,numba