几周前，我问了一个关于提高用 Python 编写的函数的速度的问题。当时，TryPyPy 让我注意到使用 Cython 的可能性。他还友好地举例说明了我如何对该代码片段进行 Cythonize 化。我想对下面的代码做同样的事情，看看通过声明变量类型可以多快。我有几个与此相关的问题。我看过 cython.org 上的教程，但我仍有一些疑问。它们密切相关:

1. 我对 C 语言一窍不通。要使用 Cython 声明变量类型，我需要学习哪些部分？
2. python列表和元组对应的C类型是什么？例如，我可以将 Cython 中的 double 用于 Python 中的 float。我要为列表做什么？通常，我在哪里可以找到给定 Python 类型对应的 C 类型。

关于我如何对下面的代码进行 Cythonize 的任何示例都会非常有帮助。我在代码中插入了注释，提供有关变量类型的信息。

class Some_class(object):
    ** Other attributes and functions **
    def update_awareness_status(self, this_var, timePd):
        '''Inputs: this_var (type: float)
           timePd (type: int)
           Output: None'''

        max_number = len(self.possibilities)
        # self.possibilities is a list of tuples.
        # Each tuple is a pair of person objects. 

        k = int(math.ceil(0.3 * max_number))
        actual_number = random.choice(range(k))
        chosen_possibilities = random.sample(self.possibilities, 
                                         actual_number)
        if len(chosen_possibilities) > 0:
            # chosen_possibilities is a list of tuples, each tuple is a pair
            # of person objects. I have included the code for the Person class
            # below.
            for p1,p2 in chosen_possibilities:

                # awareness_status is a tuple (float, int)
                if p1.awareness_status[1] < p2.awareness_status[1]:                   
                    if p1.value > p2.awareness_status[0]:
                        p1.awareness_status = (this_var, timePd)
                    else:
                        p1.awareness_status = p2.awareness_status
                elif p1.awareness_status[1] > p2.awareness_status[1]:
                    if p2.value > p1.awareness_status[0]:
                        p2.awareness_status = (price, timePd)
                    else:
                        p2.awareness_status = p1.awareness_status
                else:
                    pass     

class Person(object):                                         
    def __init__(self,id, value):
        self.value = value
        self.id = id
        self.max_val = 50000
        ## Initial awareness status.          
        self.awarenessStatus = (self.max_val, -1)

最佳答案

作为一般说明，您可以通过运行带有 -a“annotate”选项的 cython 命令来准确查看 Cython 为每个源代码行生成的 C 代码。参见 Cython documentation举些例子。这在尝试查找函数主体中的瓶颈时非常有帮助。

此外，还有 "early binding for speed" 的概念当 Cython-ing 你的代码时。 Python 对象(如下面的 Person 类的实例)使用通用 Python 代码进行属性访问，在内循环中速度很慢。我怀疑如果将 Person 类更改为 cdef class，那么您会看到一些加速。此外，您需要在内部循环中键入 p1 和 p2 对象。

由于您的代码有很多 Python 调用(例如 random.sample)，您可能不会获得巨大的加速，除非您找到一种方法将这些行放入 C 中，这需要很长时间付出的努力。

您可以将内容输入为tuple 或list，但这通常不会带来很大的加速。尽可能使用 C 数组；您必须查找的内容。

通过以下微不足道的修改，我获得了 1.6 倍的加速。请注意，我必须在这里和那里更改一些内容才能使其编译。

ctypedef int ITYPE_t

cdef class CyPerson:
    # These attributes are placed in the extension type's C-struct, so C-level
    # access is _much_ faster.
    cdef ITYPE_t value, id, max_val
    cdef tuple awareness_status

    def __init__(self, ITYPE_t id, ITYPE_t value):
        # The __init__ function is much the same as before.
        self.value = value
        self.id = id
        self.max_val = 50000
        ## Initial awareness status.          
        self.awareness_status = (self.max_val, -1)

NPERSONS = 10000

import math
import random

class Some_class(object):

    def __init__(self):
        ri = lambda: random.randint(0, 10)
        self.possibilities = [(CyPerson(ri(), ri()), CyPerson(ri(), ri())) for i in range(NPERSONS)]

    def update_awareness_status(self, this_var, timePd):
        '''Inputs: this_var (type: float)
           timePd (type: int)
           Output: None'''

        cdef CyPerson p1, p2
        price = 10

        max_number = len(self.possibilities)
        # self.possibilities is a list of tuples.
        # Each tuple is a pair of person objects. 

        k = int(math.ceil(0.3 * max_number))
        actual_number = random.choice(range(k))
        chosen_possibilities = random.sample(self.possibilities,
                                         actual_number)
        if len(chosen_possibilities) > 0:
            # chosen_possibilities is a list of tuples, each tuple is a pair
            # of person objects. I have included the code for the Person class
            # below.
            for persons in chosen_possibilities:
                p1, p2 = persons
                # awareness_status is a tuple (float, int)
                if p1.awareness_status[1] < p2.awareness_status[1]:
                    if p1.value > p2.awareness_status[0]:
                        p1.awareness_status = (this_var, timePd)
                    else:
                        p1.awareness_status = p2.awareness_status
                elif p1.awareness_status[1] > p2.awareness_status[1]:
                    if p2.value > p1.awareness_status[0]:
                        p2.awareness_status = (price, timePd)
                    else:
                        p2.awareness_status = p1.awareness_status

关于python - Cythonize Python 函数以使其更快，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/4872715/