[MPICH] How to create a Window for 2D array

[Rajeev Thakur]

To create a window for a dynamically allocated 2D array, you need to
allocate a single contiguous chunk of memory and then set up the pointers so
that it can be addressed as a 2D array. For example:

double *temp; 
error = MPI_Alloc_mem(n1D * sizeof(double*), MPI_INFO_NULL, &pp);
error = MPI_Alloc_mem(n1D * n2D * sizeof(double), MPI_INFO_NULL, &temp);  
pp[0] = temp; 
for(i=1; i<n1D; i++)
    pp[i] = pp[i-1] + n2D;
error = MPI_Win_create(pp, n1D*n2D, sizeof(double), MPI_INFO_NULL,
MPI_COMM_WORLD, &win);

Rajeev
 

> -----Original Message-----
> From: owner-mpich-discuss at mcs.anl.gov 
> [mailto:owner-mpich-discuss at mcs.anl.gov] On Behalf Of Tao He
> Sent: Thursday, January 05, 2006 5:00 PM
> To: mpich-discuss at mcs.anl.gov
> Subject: [MPICH] How to create a Window for 2D array
> 
> Dear All,
>  
> I am a newer for One Sided-Communcation. I have a question 
> how to create a window for 2D array. For example, I create a 
> 2D double array by this function:
>  
> double** NewMPI2_2DPointer(int n1D, int n2D)
> { double **pp;
>   int error;
>   error = MPI_Alloc_mem(n1D * sizeof(double*), MPI_INFO_NULL, &pp);
>   if (error != MPI_SUCCESS)
>   {
>     printf("Memory allocation failed for PP 1D array, aborting.\n");
>     MPI_Abort(MPI_COMM_WORLD, -1);
>     exit(-1);
>   }
>  
>   for(i=0; i<n1D; i++)
>   {
>     error = MPI_Alloc_mem(n2D * sizeof(double), 
> MPI_INFO_NULL, &pp[i]);
>     if (error != MPI_SUCCESS)
>     {
>         printf("Memory allocation failed for PP 1D array, 
> aborting.\n");
>         MPI_Abort(MPI_COMM_WORLD, -1);
>        exit(-1);
>     }
>   }
>  
> }
>  
> I want to create a window for this memory:
> Like:
>      error = MPI_Win_create(pp, n1D, sizeof(double*), 
> MPI_INFO_NULL, MPI_COMM_WORLD, &win);
> 
> or should be
>     error = MPI_Win_create(pp, n1D*n2D, sizeof(double), 
> MPI_INFO_NULL, MPI_COMM_WORLD, &win);
>                                         
> Which is the right? Please tell me! THanks very much!
>  
> Tao
>