C++与Fortran混编 type里值的传递和allocate相关的问题

kyra

在 Fortran 语言里。pointchain 大小是 1:3 * 1:cylinderinfo%pointcount
则 C 语言中正好相反，所以应该视为 0:cylinderinfo%pointcount-1 * 0:2

因此 fortran 中 pointchain(2,6) = 381 ，则 C 中应该输出 cout << cylinderinfo.pointchain[ (6-1)*3+(2-1) ]

kyra

问题1，无需额外处理。
问题2，不能在type里存放fortran语言的动态分配数组。否则C语言无法用标准化的手段访问。解决办法是，用 C 指针，fortran分配后把地址赋给 C 指针。具体看注释

（这方法适合于fortran的动态分配返回给 C，并不适合 C 分配的数组传递给 fortran）

[Fortran] 纯文本查看 复制代码

module hydromodelUtil
  use iso_c_binding
  implicit none
  double precision, parameter :: pi=acos(-1.d0)
  !这部分为输出值
  type ,Bind(C):: singleinfo
    integer(c_int) :: controlno
    integer(c_int) :: unittype
    integer(c_int) :: solid
    real(c_double) :: coearea
    real(c_double):: volume
    real(c_double), dimension(3) :: center
    integer (c_int):: pointcount, trianglecount
    type(C_PTR) :: pointchain , trianglechain!!!!!!!用C指针
  end type singleinfo

contains
  subroutine cylindermeshing(r, h, cylinderinfo) Bind(C,Name="cylindermeshing")
    !DEC$ ATTRIBUTES DLLEXPORT::cylindermeshing
    implicit none
    real(c_double) :: r, h
    type(singleinfo) :: cylinderinfo
    integer(c_int) :: polyedge=60
    double precision, dimension(:,:), allocatable :: point
    double precision, dimension(:,:), allocatable , target ,save :: pointchain!!!!!!!Fortran分配数组
    real(c_double) :: dtheta
    integer(c_int) :: meshi

    dtheta=2*pi/real(polyedge)

    cylinderinfo%volume=(0.5d0*polyedge*sin(dtheta)*r**2)*h
    cylinderinfo%center=(/ 0.0d0, 0.0d0, 0.5d0*h /)
    cylinderinfo%pointcount=2*polyedge
    cylinderinfo%trianglecount=4*polyedge
    allocate(point(2,polyedge+1) )
    allocate(pointchain(3,cylinderinfo%pointcount) )!!!!!!!

    do meshi=1, polyedge, 1
      point(1,meshi)=r*cos( (real(meshi)-1.0d0)*dtheta)
      point(2,meshi)=r*sin( (real(meshi)-1.0d0)*dtheta)
    end do
    point(:, polyedge+1)=point(:, 1)

    do meshi=1, polyedge, 1
      pointchain(1:2,meshi)=point(1:2,meshi)
      pointchain(3,meshi)=0.0d0
      pointchain(1:2,polyedge+meshi)=point(1:2,meshi)
      pointchain(3,polyedge+meshi)=h
    end do
    cylinderinfo%pointchain = c_loc( pointchain )!!!!!!!把地址给C指针
  end subroutine cylindermeshing
  
end module hydromodelUtil

[C++] 纯文本查看 复制代码

#include <iostream>

struct singleinfo{
  int controlno;
  int unittype;
  int solid;
  double coearea;
  double volume;
  double center[3];
  int pointcount , trianglecount;
  double *pointchain , *trianglechain;/////// C 指针
};

extern "C" {
  void cylindermeshing( double & , double & , struct singleinfo *  );
  double thirddet( double * );
}

using namespace std;

int main()
{
  struct singleinfo cylinderinfo;
  double r = 3.0;
  double h = 4.0;
  cylinderinfo.controlno  = 1;
  cylinderinfo.unittype   = 2;
  cylinderinfo.solid      = 3;
  cylinderinfo.coearea    = 4;
  cylinderinfo.volume     = 5;
  cylinderinfo.unittype   = 6;
  cylinderinfo.pointcount = 7;
  cylinderinfo.trianglecount = 8;
  cylinderinfo.center[0] = 11;
  cylinderinfo.center[1] = 11;
  cylinderinfo.center[2] = 11;
  cylindermeshing(r, h, &cylinderinfo);
  double deta[3][3];
  for (int i = 0; i < 3; i++){
    for (int j = 0; j < 3; j++){
      deta[j][i] = j*4 + i;
    }
  }
  cout << cylinderinfo.pointchain[0] << endl;
}

kyra

不需要转换。使用的时候注意顺序即可。