C++ Python Ctypes调用C++；功能

我尝试使用Python cType来与发布的（封闭源代码）C++库接口。I（尝试）编写了一个基本的C样式函数包装器来构造C++向量样式对象并调用C++例程。我还（尝试）编写了一个基本的python脚本来加载共享库。除了调用C++例程的行外，其他都在工作：

*** glibc detected *** python: free(): invalid next size (fast): 0x0000000001e73c00 ***

#include "nr3.h"
#include "cholesky.h"
#include "gaumixmod.h"

extern "C" {

  void cGaumixmod(double* D, int Dm, int Dn,  double* M, int Mm, int Mn) {

    MatDoub ddata(Dm,Dn,*D); // construct Matrix (vector) type                       
    MatDoub mmeans(Mm,Mn,*M); // construct Matrix (vector) type                      

    //XXX test numpy array is coming through as C array and we can rw, checks OK
    int i;
    // for(i=0;i<Dn*Dm;++i) {                                               
    //   printf("Address %x : ",(D+i));                                     
    //   printf("was %f \t" , D[i]);                                        
    //   D[i]+=1.0;                                                         
    //   printf("now: %f \n" , D[i]);                                       
    // }                                                                    

    // check that array D was copied to matrix ddata, and we can r/w
    for(i=0;i<Dm*Dn;++i) {
      printf("iter %d Address %x : ",i,ddata[i/Dm][i%Dm]);
      printf("was %f \t" , ddata[i/Dm][i%Dm]);
      ddata[i/Dm][i%Dm]+=1.0;
      printf("now: %f \n" ,ddata[i/Dm][i%Dm]);
    }


    Gaumixmod::Gaumixmod(ddata,mmeans);

    //return data from vector to ctypes array C so we can check data returns to python
    //via numpy array, checks ok
    for(i=0;i<Dm*Dn;++i) {
      D[i] = ddata[i/Dm][i%Dm];
    }


  }

}

这里是文件，不幸的是我不能共享标题，但如果需要，我可以写一些类似的东西

#include "nr3.h"
#include "cholesky.h"
#include "gaumixmod.h"

extern "C" {

  void cGaumixmod(double* D, int Dm, int Dn,  double* M, int Mm, int Mn) {

    MatDoub ddata(Dm,Dn,*D); // construct Matrix (vector) type                       
    MatDoub mmeans(Mm,Mn,*M); // construct Matrix (vector) type                      

    //XXX test numpy array is coming through as C array and we can rw, checks OK
    int i;
    // for(i=0;i<Dn*Dm;++i) {                                               
    //   printf("Address %x : ",(D+i));                                     
    //   printf("was %f \t" , D[i]);                                        
    //   D[i]+=1.0;                                                         
    //   printf("now: %f \n" , D[i]);                                       
    // }                                                                    

    // check that array D was copied to matrix ddata, and we can r/w
    for(i=0;i<Dm*Dn;++i) {
      printf("iter %d Address %x : ",i,ddata[i/Dm][i%Dm]);
      printf("was %f \t" , ddata[i/Dm][i%Dm]);
      ddata[i/Dm][i%Dm]+=1.0;
      printf("now: %f \n" ,ddata[i/Dm][i%Dm]);
    }


    Gaumixmod::Gaumixmod(ddata,mmeans);

    //return data from vector to ctypes array C so we can check data returns to python
    //via numpy array, checks ok
    for(i=0;i<Dm*Dn;++i) {
      D[i] = ddata[i/Dm][i%Dm];
    }


  }

}

gaumixmod.cpp：

#include "nr3.h"
#include "cholesky.h"
#include "gaumixmod.h"

extern "C" {

  void cGaumixmod(double* D, int Dm, int Dn,  double* M, int Mm, int Mn) {

    MatDoub ddata(Dm,Dn,*D); // construct Matrix (vector) type                       
    MatDoub mmeans(Mm,Mn,*M); // construct Matrix (vector) type                      

    //XXX test numpy array is coming through as C array and we can rw, checks OK
    int i;
    // for(i=0;i<Dn*Dm;++i) {                                               
    //   printf("Address %x : ",(D+i));                                     
    //   printf("was %f \t" , D[i]);                                        
    //   D[i]+=1.0;                                                         
    //   printf("now: %f \n" , D[i]);                                       
    // }                                                                    

    // check that array D was copied to matrix ddata, and we can r/w
    for(i=0;i<Dm*Dn;++i) {
      printf("iter %d Address %x : ",i,ddata[i/Dm][i%Dm]);
      printf("was %f \t" , ddata[i/Dm][i%Dm]);
      ddata[i/Dm][i%Dm]+=1.0;
      printf("now: %f \n" ,ddata[i/Dm][i%Dm]);
    }


    Gaumixmod::Gaumixmod(ddata,mmeans);

    //return data from vector to ctypes array C so we can check data returns to python
    //via numpy array, checks ok
    for(i=0;i<Dm*Dn;++i) {
      D[i] = ddata[i/Dm][i%Dm];
    }


  }

}

我编译这个jazz时使用了：

#include "nr3.h"
#include "cholesky.h"
#include "gaumixmod.h"

extern "C" {

  void cGaumixmod(double* D, int Dm, int Dn,  double* M, int Mm, int Mn) {

    MatDoub ddata(Dm,Dn,*D); // construct Matrix (vector) type                       
    MatDoub mmeans(Mm,Mn,*M); // construct Matrix (vector) type                      

    //XXX test numpy array is coming through as C array and we can rw, checks OK
    int i;
    // for(i=0;i<Dn*Dm;++i) {                                               
    //   printf("Address %x : ",(D+i));                                     
    //   printf("was %f \t" , D[i]);                                        
    //   D[i]+=1.0;                                                         
    //   printf("now: %f \n" , D[i]);                                       
    // }                                                                    

    // check that array D was copied to matrix ddata, and we can r/w
    for(i=0;i<Dm*Dn;++i) {
      printf("iter %d Address %x : ",i,ddata[i/Dm][i%Dm]);
      printf("was %f \t" , ddata[i/Dm][i%Dm]);
      ddata[i/Dm][i%Dm]+=1.0;
      printf("now: %f \n" ,ddata[i/Dm][i%Dm]);
    }


    Gaumixmod::Gaumixmod(ddata,mmeans);

    //return data from vector to ctypes array C so we can check data returns to python
    //via numpy array, checks ok
    for(i=0;i<Dm*Dn;++i) {
      D[i] = ddata[i/Dm][i%Dm];
    }


  }

}

g++ -fPIC -c gaumixmod.cpp;
g++ -shared -o gaumixmod.so gaumixmod.o

跑

#include "nr3.h"
#include "cholesky.h"
#include "gaumixmod.h"

extern "C" {

  void cGaumixmod(double* D, int Dm, int Dn,  double* M, int Mm, int Mn) {

    MatDoub ddata(Dm,Dn,*D); // construct Matrix (vector) type                       
    MatDoub mmeans(Mm,Mn,*M); // construct Matrix (vector) type                      

    //XXX test numpy array is coming through as C array and we can rw, checks OK
    int i;
    // for(i=0;i<Dn*Dm;++i) {                                               
    //   printf("Address %x : ",(D+i));                                     
    //   printf("was %f \t" , D[i]);                                        
    //   D[i]+=1.0;                                                         
    //   printf("now: %f \n" , D[i]);                                       
    // }                                                                    

    // check that array D was copied to matrix ddata, and we can r/w
    for(i=0;i<Dm*Dn;++i) {
      printf("iter %d Address %x : ",i,ddata[i/Dm][i%Dm]);
      printf("was %f \t" , ddata[i/Dm][i%Dm]);
      ddata[i/Dm][i%Dm]+=1.0;
      printf("now: %f \n" ,ddata[i/Dm][i%Dm]);
    }


    Gaumixmod::Gaumixmod(ddata,mmeans);

    //return data from vector to ctypes array C so we can check data returns to python
    //via numpy array, checks ok
    for(i=0;i<Dm*Dn;++i) {
      D[i] = ddata[i/Dm][i%Dm];
    }


  }

}

python gaumixmod.py

我的研究表明，这个错误类似于segFault，python试图访问超出其范围的内存。。。这是我不理解的部分，因为注释C++行GAUMIXMOD::GUMIXMODE（），所有的工作都很好，并且例程应该在CGAUMIXMODE（）函数中实例化的向量上运行，而不是Python Nuffy数组。我对C++非常陌生，虽然我已经多次使用C类型来支持C库。我希望有C++、Python和cType体验的人能在这里提供一些见解/指导。

#include "nr3.h"
#include "cholesky.h"
#include "gaumixmod.h"

extern "C" {

  void cGaumixmod(double* D, int Dm, int Dn,  double* M, int Mm, int Mn) {

    MatDoub ddata(Dm,Dn,*D); // construct Matrix (vector) type                       
    MatDoub mmeans(Mm,Mn,*M); // construct Matrix (vector) type                      

    //XXX test numpy array is coming through as C array and we can rw, checks OK
    int i;
    // for(i=0;i<Dn*Dm;++i) {                                               
    //   printf("Address %x : ",(D+i));                                     
    //   printf("was %f \t" , D[i]);                                        
    //   D[i]+=1.0;                                                         
    //   printf("now: %f \n" , D[i]);                                       
    // }                                                                    

    // check that array D was copied to matrix ddata, and we can r/w
    for(i=0;i<Dm*Dn;++i) {
      printf("iter %d Address %x : ",i,ddata[i/Dm][i%Dm]);
      printf("was %f \t" , ddata[i/Dm][i%Dm]);
      ddata[i/Dm][i%Dm]+=1.0;
      printf("now: %f \n" ,ddata[i/Dm][i%Dm]);
    }


    Gaumixmod::Gaumixmod(ddata,mmeans);

    //return data from vector to ctypes array C so we can check data returns to python
    //via numpy array, checks ok
    for(i=0;i<Dm*Dn;++i) {
      D[i] = ddata[i/Dm][i%Dm];
    }


  }

}

---

谢谢

有一个用于与C接口的新库，您可以查看它：

#include "nr3.h"
#include "cholesky.h"
#include "gaumixmod.h"

extern "C" {

  void cGaumixmod(double* D, int Dm, int Dn,  double* M, int Mm, int Mn) {

    MatDoub ddata(Dm,Dn,*D); // construct Matrix (vector) type                       
    MatDoub mmeans(Mm,Mn,*M); // construct Matrix (vector) type                      

    //XXX test numpy array is coming through as C array and we can rw, checks OK
    int i;
    // for(i=0;i<Dn*Dm;++i) {                                               
    //   printf("Address %x : ",(D+i));                                     
    //   printf("was %f \t" , D[i]);                                        
    //   D[i]+=1.0;                                                         
    //   printf("now: %f \n" , D[i]);                                       
    // }                                                                    

    // check that array D was copied to matrix ddata, and we can r/w
    for(i=0;i<Dm*Dn;++i) {
      printf("iter %d Address %x : ",i,ddata[i/Dm][i%Dm]);
      printf("was %f \t" , ddata[i/Dm][i%Dm]);
      ddata[i/Dm][i%Dm]+=1.0;
      printf("now: %f \n" ,ddata[i/Dm][i%Dm]);
    }


    Gaumixmod::Gaumixmod(ddata,mmeans);

    //return data from vector to ctypes array C so we can check data returns to python
    //via numpy array, checks ok
    for(i=0;i<Dm*Dn;++i) {
      D[i] = ddata[i/Dm][i%Dm];
    }


  }

}

---

看看您的_gaumixmod.argtypes行。np.ctypeslib.ndpointer（dtype=np.float64，flags='C_continuous'）真的是一种类型吗？我会尝试使用ctypes.POINTER（ctypes.c_double）来确定。因为“C_contract”与指针类型无关，因为它只指向内存中的某个位置。另一种情况可能更为可能_gaumixmod（D，…）正在寻找一个double*，您正在给它一个np.array。如果没有其他内容，它应该是D.ctypes.data_as（ctypes.POINTER（ctypes.c_double））您是否考虑过使用Cython？@K.Brafford，好建议。与尝试使用ctypes相比，这种方法更不容易出错。

#include "nr3.h"
#include "cholesky.h"
#include "gaumixmod.h"

extern "C" {

  void cGaumixmod(double* D, int Dm, int Dn,  double* M, int Mm, int Mn) {

    MatDoub ddata(Dm,Dn,*D); // construct Matrix (vector) type                       
    MatDoub mmeans(Mm,Mn,*M); // construct Matrix (vector) type                      

    //XXX test numpy array is coming through as C array and we can rw, checks OK
    int i;
    // for(i=0;i<Dn*Dm;++i) {                                               
    //   printf("Address %x : ",(D+i));                                     
    //   printf("was %f \t" , D[i]);                                        
    //   D[i]+=1.0;                                                         
    //   printf("now: %f \n" , D[i]);                                       
    // }                                                                    

    // check that array D was copied to matrix ddata, and we can r/w
    for(i=0;i<Dm*Dn;++i) {
      printf("iter %d Address %x : ",i,ddata[i/Dm][i%Dm]);
      printf("was %f \t" , ddata[i/Dm][i%Dm]);
      ddata[i/Dm][i%Dm]+=1.0;
      printf("now: %f \n" ,ddata[i/Dm][i%Dm]);
    }


    Gaumixmod::Gaumixmod(ddata,mmeans);

    //return data from vector to ctypes array C so we can check data returns to python
    //via numpy array, checks ok
    for(i=0;i<Dm*Dn;++i) {
      D[i] = ddata[i/Dm][i%Dm];
    }


  }

}