【发布时间】：2014-09-20 21:15:10
【问题描述】：
我想在 python 中对代码进行 cythonize 以加快代码速度。在下面你可以看到我试图让我的 python 类可以被 cython 理解：
import numpy as np
cimport numpy as np
ctypedef np.double_t DTYPE_T
cpdef double std_G,v_c
std_G=4.3e-9 # Newton's const in Mpc (km/s)^2 M_sol^{-1}
v_c = 299792.458 #km/s
cdef extern from "math.h":
double log(double) nogil
double sqrt(double) nogil
cdef extern from "gsl/gsl_math.h":
ctypedef struct gsl_function:
double (* function) (double x, void * params)
void * params
cdef extern from "gsl/gsl_integration.h":
ctypedef struct gsl_integration_workspace
gsl_integration_workspace * gsl_integration_workspace_alloc(size_t n)
void gsl_integration_workspace_free(gsl_integration_workspace * w)
int gsl_integration_qags(const gsl_function * f, double a, double b, double epsabs, double epsrel, size_t limit, gsl_integration_workspace * workspace, double *result, double *abserr)
cdef double do_callback(double x, void* params):
return (<ComovingDistMemoization>params).eval(x)
cdef class ComovingDistMemoization(object):
cdef list _memotable
cdef cosmolgy
def __cinit__(self, cosmology, memotable = None):
if memotable is None:
self._memotable = []
self._memotable = memotable
self.cosmology = cosmology
def __call__(self, double z):
if z in self._memotable:
return self._memotable[z]
def eval(z):
return 1./sqrt(self.cosmology.hubble2(z))
cdef gsl_integration_workspace* w =gsl_integration_workspace_alloc(1000)
cdef gsl_function F
F.function = &do_callback
F.params = <void*>self
cdef double result = 3, error = 5
cdef double y, err, dist
gsl_integration_qags (&F, 0, z, 0, 1e-7, 1000, w, &result, &error)
y, err = result, error
gsl_integration_workspace_free(w)
dist = self.cosmology.v_c * y #to get proper units, ie to put in the hubble length
self._memotable[z] = dist
return dist
cdef class cosmology(object):
cdef comovingdist
cdef public double omega_m, omega_l, h, w, omega_r, G, v_c
cdef double H0, hubble_length
def __init__(self, omega_m = 0.3, omega_l = 0.7, h = 0.7, w = -1, omega_r = 0., G = std_G):
self.omega_m = omega_m
self.omega_l = omega_l
self.omega_r = omega_r
self.h = h
self.w = w
self.G = G
self.v_c = v_c
self.comovingdist = ComovingDistMemoization(self)
def __copy__(self):
return cosmology(omega_m = self.omega_m, omega_l = self.omega_l, h = self.h, w = self.w, omega_r = self.omega_r, G = self.G)
property H0:
def __get__(self):
return 100*self.h #km/s/MPC
def hubble2(self, double z):
cdef double inv_a
inv_a = 1.+z
return (self.omega_r*inv_a**4 + self.omega_m*inv_a**3 + \
self.omega_l*(inv_a**(3*(1+self.w))) + (1 - self.omega_m - self.omega_l - self.omega_r)*inv_a**2)*self.H0**2
property hubble_length:
def __get__(self):
return self.v_c / self.H0
def rho_crit(self, double z):
return 3.*self.hubble2(z)/(8*np.pi*self.G)
def angulardist(self, double z, double z2 = None):
if z2 is None:
return self.comovingdist(z) / (1+z)
return (self.comovingdist(z2) - self.comovingdist(z)) / (1+z2)
但是，引发错误的地方之一，到目前为止我找不到任何替换，我的调查刚刚达到这一点，即 cython 不支持 __copy__(self) 函数。
第一个问题：如何在cython 中复制class 的一种方法？
我用pickle.Pickler 读到，可以为类的实例提供替换，但我不知道它应该如何在类中生成类的copy？
更新：
用以下代码替换__copy__是否正确：
def __reduce__(self):
return (self.__class__, (), self.__getstate__())
def __getstate__(self):
return (self.omega_m, self.omega_l, self.omega_r, self.h, self.w, self.G, self.v_c)
def __setstate__(self, data):
(self.omega_m, self.omega_l, self.omega_r, self.h, self.w, self.G, self.v_c) = data
我的第二个问题是关于 property，我是否在 cython 中定义了该属性，或者我还需要一个 __set__ 函数？
我的最后一个问题：当我使用 ComovingDistMemoization 调用 cosmology 类的所有实例时，它们返回零。我想知道我在ComovingDistMemoization 类中调用例如cosmology 类的方式是否会导致问题，并且不能在它们之间传递信息？
【问题讨论】：
-
我对 cython 知之甚少，但是您当前的
__copy__代码在常规 Python 中不起作用，因为当您尝试在类名开始时调用Cosmology时使用的是大写 C用小写字母 c。我也不确定为什么您根本需要__copy__方法，因为您似乎没有在其中做任何花哨的事情（如果没有定义该方法，常规 Python 类的功能完全相同）。 -
@Blckknght 哈哈！你说的对。我更新了它。但是我仍然想知道它是否可以替换为
pickle.Pickler以及如何替换？另外一点__copy__是否符合 cython 条件，哪个更快__copy__或使用 pickle？ -
@Dalek 下面的答案是否解决了您关于财产的这个问题？
-
@SaulloCastro 不幸的是，在 cython 中定义这样的属性不起作用！