使用MPI_Gather在c++中3d数组

我正在尝试并行化for循环操作，该操作夹在两个for循环之间。

在每个处理器中计算完数据(3d数组)后，我想将每个处理器的数据收集回根节点以进行进一步处理。我尝试使用MPI_Gather函数将数据返回到根节点。使用此函数，从根处理器收集回数据，但不从其他处理器收集数据。

int main(int argc, char * argv[]) {
  int i,k,l,j;
  int Np = 7, Nz = 7, Nr = 4;
  int mynode, totalnodes;
  MPI_Status status;
  long double ***k_p, ***k_p1; 
  int startvalp,endvalp;
  MPI_Init(&argc,&argv);
  MPI_Comm_size(MPI_COMM_WORLD, &totalnodes);
  MPI_Comm_rank(MPI_COMM_WORLD, &mynode);
  // Allocation of memory
  Allocate_3D_R(k_p,(Nz+1),(Np+1),(Nr+1));
  Allocate_3D_R(k_p1,(Nz+1),(Np+1),(Nr+1));
  // startvalp represents the local starting value for each processor
  // endvalp represents the local ending value for each processor
  startvalp = (Np+1)*mynode/totalnodes - 0;
  endvalp = startvalp + (((Np+1)/totalnodes) -1);
  for(l = 0 ; l <= 1 ; l++){
    for(k=startvalp; k<=endvalp; k++){
      // for loop parallelized between the processors 
      // original loop: for(k=0; k<= Np; k++) 
      for(i=0; i<=1; i++){
        k_p[i][k][l] =  l+k+i;
      }
    }
  }
  // For Np = 7  and for two processors ; 
  //   k = 0 - 3 is calculated in processor 0;
  //   k = 4 - 7 is calculated in processor 1;
  // Now I need to collect the value of k_p from processor 1 
  // back to the root processor.
  // MPI_Gather function  is used.
  for(l = 0 ; l <= 1 ; l++){
    for(k=startvalp; k<=endvalp; k++){      
      for(i=0; i<=1; i++){
        MPI_Gather(&(k_p[i][k][l]),1, MPI_LONG_DOUBLE,&(k_p1[i][k][l]),1, MPI_LONG_DOUBLE, 0, MPI_COMM_WORLD);
      }
    }
  }
  // Using this the k_p is collected from root processor and stored
  // in the k_p1 variable, but from the slave processor it is not
  // collected back to the root processor.
  if(mynode == 0){
    for(l = 0 ; l <= 1 ; l++){
      for(k=0; k<=Np; k++){
        for(i=0i<=1;i++){
          cout << "Processor "<<mynode;
          cout << ": k_p["<<i<<"]["<<k<<"]["<<l<<"] = " <<k_p1[i][k][l]<<endl;
        }
      }
    }
  }
  MPI_Finalize();
} // end of main

void Allocate_3D_R(long double***& m, int d1, int d2, int d3) {
  m=new long double** [d1];
  for (int i=0; i<d1; ++i) {
    m[i]=new long double* [d2];
    for (int j=0; j<d2; ++j) {
      m[i][j]=new long double [d3];
      for (int k=0; k<d3; ++k) {
        m[i][j][k]=0.0;
      }
    }
  }
}

输出如下:

Processor 0: k_p[0][0][0] = 0
Processor 0: k_p[1][0][0] = 1
Processor 0: k_p[0][1][0] = 1
Processor 0: k_p[1][1][0] = 2
Processor 0: k_p[0][2][0] = 2
Processor 0: k_p[1][2][0] = 3
Processor 0: k_p[0][3][0] = 3
Processor 0: k_p[1][3][0] = 4
Processor 0: k_p[0][4][0] = 0
Processor 0: k_p[1][4][0] = 0
Processor 0: k_p[0][5][0] = 0
Processor 0: k_p[1][5][0] = 0
Processor 0: k_p[0][6][0] = 0
Processor 0: k_p[1][6][0] = 0
Processor 0: k_p[0][7][0] = 0
Processor 0: k_p[1][7][0] = 0
Processor 0: k_p[0][0][1] = 1
Processor 0: k_p[1][0][1] = 2
Processor 0: k_p[0][1][1] = 2
Processor 0: k_p[1][1][1] = 3
Processor 0: k_p[0][2][1] = 3
Processor 0: k_p[1][2][1] = 4
Processor 0: k_p[0][3][1] = 4
Processor 0: k_p[1][3][1] = 5
Processor 0: k_p[0][4][1] = 0
Processor 0: k_p[1][4][1] = 0
Processor 0: k_p[0][5][1] = 0
Processor 0: k_p[1][5][1] = 0
Processor 0: k_p[0][6][1] = 0
Processor 0: k_p[1][6][1] = 0
Processor 0: k_p[0][7][1] = 0
Processor 0: k_p[1][7][1] = 0

根处理器的数据被传输，但不从其他处理器传输。我尝试使用MPI_Send和MPI_Recv函数，没有遇到上述问题，但对于for循环的大值，它需要更多的时间。

因此，有人能提供解决上述问题的方法吗?