python - 导入SWIG+python模块报错"undefined symbol"

Question

我使用 SWIG 创建了一个用于 Python 的 *.so 文件，但是当我导入它时，我得到了这个:

/_analyzer.so: undefined symbol: autocorellation

我几乎按照以下说明做了所有事情:https://scipy.github.io/old-wiki/pages/Cookbook/SWIG_NumPy_examples.html

我的代码如下:

分析器.h:

void autocorellation(double *in, double *out, long long n);

分析器.cpp:

#include "analyzer.h"
#include <math.h>
#include <stdlib.h>

#define PI 3.14159265358979323846

typedef struct {
    double real;
    double im;
} Complex;

void complex_multiply(Complex a,Complex b,Complex* c){
    c->real = a.real * b.real - a.im * b.im;
    c->im = a.real * b.im + a.im * b.real;
}

void complex_multiply_int(int a, Complex b,Complex* c){
    c->real = a * b.real;
    c->im = a * b.im;
}

void complex_sum(Complex a,Complex b,Complex* c){
    c->real = a.real + b.real;
    c->im = a.im + b.im;
}

void complex_conjugate(Complex* a,Complex* b,long long n){
    for(int i = 0; i < n; ++i){
        b[i].real = a[i].real;
        b[i].im = -1 * a[i].im;
    }
}

long long rev (long long num, long long lg_n) {
    long long res = 0;
    for (long long i=0; i < lg_n; ++i)
        if (num & (1 << i))
            res |= 1 << (lg_n-1-i);
    return res;
}

void fft (Complex* a, long long n,bool invert) {
    long long lg_n = 0;
    while ((1 << lg_n) < n)
        ++lg_n;
    for (long long  i=0; i<n; ++i){
        long long r= rev(i,lg_n);
        if (i < r){
            a[i].real = a[i].real +  a[r].real;
            a[r].real = a[i].real -  a[r].real;
            a[i].real = a[i].real -  a[r].real;
            a[i].im = a[i].im +  a[r].im;
            a[r].im = a[i].im -  a[r].im;
            a[i].im = a[i].im -  a[r].im;
        }
    }
    for (long long len=2; len<=n; len <<= 1) {
        double ang = 2*PI/len * (invert ? -1 : 1);
        Complex wn;
        wn.real = cos(ang);
        wn.im = sin(ang);
        for (long long i=0; i<n; i+=len) {
            Complex w;
            w.real = 1;
            w.im = 0;
            long long ll = (long long)(len * 0.5);
            for (long long j=0; j< ll; ++j) {
                Complex u = a[i+j],v;
                complex_multiply(a[i+j+ll],w,&v);
                complex_sum(u,v,&a[i+j]);
                complex_multiply_int(-1,v,&v);
                complex_sum(u,v,&a[i+j+ll]);
                complex_multiply(w,wn,&w);
            }
        }
    }
    if (invert)
        for (long long i=0; i<n; ++i){
            a[i].real /= n;
            a[i].im /= n;
        }
}

void autocorellation(double *in, double *out, long long n){
    long long le = 1;
    while(n > le)
        le *= 2;
    double m = 0;
    for(int i = 0; i < n; ++i)
        m+=in[i];
    m /= n;
    for(int i = 0; i < n; ++i)
        in[i] -= m;
    Complex* a = (Complex*) malloc(le*sizeof(Complex));
    Complex* b = (Complex*) malloc(le*sizeof(Complex));
    for(long long i = 0; i < n; ++i){
        a[i].im = 0;
        a[i].real = in[i];
    }
    for(long long i = n; i < le; ++i){
        a[i].im = 0;
        a[i].real = 0;
    }
    fft(a,le,false);
    complex_conjugate(a,b,le);
    Complex* c = (Complex*) malloc(le*sizeof(Complex));
    for(long long i = 0; i < le; ++i)
        complex_multiply(b[i],a[i],&c[i]);
    fft(c,le,true);
    for(long long i = 0; i < n; ++i)
        out[i] = (c[i].real/c[0].real);
    free(a);
    free(b);
    free(c);
}

分析器.i:

    %module analyzer

%{
    #define SWIG_FILE_WITH_INIT
    #include "analyzer.h"
%}

%include "numpy.i"

%init %{
    import_array();
%}

%apply (double* IN_ARRAY1,int DIM1) {(double *in, long long n)}
%apply (double* ARGOUT_ARRAY1,int DIM1) {(double *out, long long n)}
%include "analyzer.h"

设置.py:

    #! /usr/bin/env python

# System imports
from distutils.core import *
from distutils      import sysconfig

# Third-party modules - we depend on numpy for everything
import numpy

# Obtain the numpy include directory.  This logic works across numpy versions.
try:
    numpy_include = numpy.get_include()
except AttributeError:
    numpy_include = numpy.get_numpy_include()

# ezrange extension module
_analyzer = Extension("_analyzer",
                   ["analyzer.i","analyzer.cpp"],
                   include_dirs = [numpy_include],
                   )

# ezrange setup
setup(  name        = "range function",
        description = "Autocorellation function evaluation",
        author      = "Bodya",
        version     = "1.0",
        ext_modules = [_analyzer]
        )

Answer 1

您的代码与食谱示例之间的区别在于您的代码是 C++。因此，您需要将 -c++ 选项传递给 SWIG。在setup.py中构造Extension(...)，只需添加swig_opts=['-c++'],即可。

请注意，distutils 仍会在生成的包装文件上调用 C 编译器，但这将具有 .cpp 扩展名，因此如果编译器是 gcc 或 clang，它应该可以正确编译。

我使用 distutils 或 setuptools 进行 C++ SWIG 扩展的经验很差，甚至稍微超出了微不足道，所以我调用 SWIG 在 distutils 之外生成一个包装器(我通过 Makefile 完成)并且只使用 distutils 来编译扩展来自包装文件。