scipy.integrate.quad ctypes函数错误“ quadpack.error：quad：第一个参数是签名不正确的ctypes函数指针”。 [英] scipy.integrate.quad ctypes function error "quadpack.error: quad: first argument is a ctypes function pointer with incorrect signature"

问题描述

我正在尝试将 scipy.integrate.nquad 与 ctypes 函数一起使用。我完全按照使用以下方法进行快速集成的说明进行操作Ctypes 。

I am trying to use scipy.integrate.nquad with a ctypes function. I exactly followed the instruction on Faster integration using Ctypes.

ctypes 集成可以用几个简单的方法完成步骤：

ctypes integration can be done in a few simple steps:

1. 在C中用函数签名 double f（int n，double args [n ]），其中 args 是一个包含函数 f 的参数的数组。 / li>
   

1. Write an integrand function in C with the function signature double f(int n, double args[n]), where args is an array containing the arguments of the function f.

//testlib.c

double f(int n, double args[n])    
{
   return args[0] - args[1] * args[2]; //corresponds to x0 - x1 * x2
}

1. 现在将此文件编译为共享/动态库（快速搜索将对此有所帮助，因为它与操作系统有关）。用户必须链接使用的所有数学库等。在Linux上看起来像这样：

$ gcc -shared -o testlib.so -fPIC testlib.c

输出库将被称为 testlib.so ，但文件扩展名可能不同。现在已经创建了一个库，可以使用 ctypes 将其加载到Python中。

The output library will be referred to as testlib.so, but it may have a different file extension. A library has now been created that can be loaded into Python with ctypes.

1. 使用 ctypes 将共享库加载到Python中，并设置 restypes 和 argtypes -这允许Scipy正确解释函数
   ：

1. Load shared library into Python using ctypes and set restypes and argtypes - this allows Scipy to interpret the function correctly:

>>> import ctypes

>>> from scipy import integrate

>>> lib = ctypes.CDLL('/**/testlib.so') # Use absolute path to testlib

>>> func = lib.f # Assign specific function to name func (for simplicity)

>>> func.restype = ctypes.c_double

>>> func.argtypes = (ctypes.c_int, ctypes.c_double)

请注意，argtypes始终为（ctypes.c_int，ctypes.c_double）而不考虑参数的数量，并且restype始终为 ctypes.c_double 。

Note that the argtypes will always be (ctypes.c_int, ctypes.c_double) regardless of the number of parameters, and restype will always be ctypes.c_double.

1. 现在像往常一样集成库函数，这里使用 nquad ：

1. Now integrate the library function as normally, here using nquad:

>>> integrate.nquad(func, [[0,10],[-10,0],[-1,1]])

(1000.0, 1.1102230246251565e-11)

但是，在最后一步，我没有得到积分的结果，但是而是显示以下错误：

However, at the final step, I didn't get the result of the integral, but the following errors instead:

>>> integrate.nquad(func,[[0,1.0],[-2.0,3.0],[1.0,2.0]])

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>

  File "/home/bfn097/apps/scipy/0.13.3_mkl-11.1.2_gcc-4.4.7/lib64/python/scipy/integrate/quadpack.py", line 618, in nquad
      return _NQuad(func, ranges, opts).integrate(*args)

  File "/home/bfn097/apps/scipy/0.13.3_mkl-11.1.2_gcc-4.4.7/lib64/python/scipy/integrate/quadpack.py", line 670, in integrate

    value, abserr = quad(f, low, high, args=args, **opt)

  File "/home/bfn097/apps/scipy/0.13.3_mkl-11.1.2_gcc-4.4.7/lib64/python/scipy/integrate/quadpack.py", line 254, in quad

    retval = _quad(func,a,b,args,full_output,epsabs,epsrel,limit,points)

  File "/home/bfn097/apps/scipy/0.13.3_mkl-11.1.2_gcc-4.4.7/lib64/python/scipy/integrate/quadpack.py", line 319, in _quad

    return _quadpack._qagse(func,a,b,args,full_output,epsabs,epsrel,limit)

  File "/home/bfn097/apps/scipy/0.13.3_mkl-11.1.2_gcc-4.4.7/lib64/python/scipy/integrate/quadpack.py", line 670, in integrate

    value, abserr = quad(f, low, high, args=args, **opt)

  File "/home/bfn097/apps/scipy/0.13.3_mkl-11.1.2_gcc-4.4.7/lib64/python/scipy/integrate/quadpack.py", line 254, in quad

    retval = _quad(func,a,b,args,full_output,epsabs,epsrel,limit,points)

  File "/home/bfn097/apps/scipy/0.13.3_mkl-11.1.2_gcc-4.4.7/lib64/python/scipy/integrate/quadpack.py", line 319, in _quad

    return _quadpack._qagse(func,a,b,args,full_output,epsabs,epsrel,limit)

  File "/home/bfn097/apps/scipy/0.13.3_mkl-11.1.2_gcc-4.4.7/lib64/python/scipy/integrate/quadpack.py", line 670, in integrate

    value, abserr = quad(f, low, high, args=args, **opt)

  File "/home/bfn097/apps/scipy/0.13.3_mkl-11.1.2_gcc-4.4.7/lib64/python/scipy/integrate/quadpack.py", line 254, in quad

    retval = _quad(func,a,b,args,full_output,epsabs,epsrel,limit,points)

  File "/home/bfn097/apps/scipy/0.13.3_mkl-11.1.2_gcc-4.4.7/lib64/python/scipy/integrate/quadpack.py", line 319, in _quad

    return _quadpack._qagse(func,a,b,args,full_output,epsabs,epsrel,limit)

quadpack.error: quad: first argument is a ctypes function pointer with incorrect signature

我正在使用gcc-4.4.7 ，python 2.6.6，numpy-1.7.1，scipy-0.13.3

I am using gcc-4.4.7,python 2.6.6, numpy-1.7.1, scipy-0.13.3

推荐答案

自变量的类型应为： ctypes.POINTER（ctypes.c_double）

The type of the argument should be: ctypes.POINTER(ctypes.c_double)

但是您是否考虑过使用 cffi ？除了比 ctypes 快外，您还不必手写参数，只需复制C声明并让 cffi 解析它们。

But have you considered using cffi? Besides being faster than ctypes, you also don't have to hand-write the argument stuff, just copy the C declarations and let cffi parse them.

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