RGX_Find_Task_Grid_endpts

Determine local task grid's end-points coodinates

Synopsis


int RGX_Find_Task_Grid_endpts(
                               MPI_Comm    Comm,
                               int         Ndim,
                               int         Glb_Grid_sz[],

                               int         task_Grid_endpts[]
                             )

Unmodified Input Variables

Comm - Input Communicator of all the tasks involved.
Ndim - Dimensionality of the Grid (Integer).
Glb_Grid_sz - Integer Array, of size Ndim, specifies the maximum grid size of the global grid. Glb_Grid_sz[ ii ] is the maximum grid size in the dimension ii, where the minimum is assumed to be 1.

Modified Output Variables

task_Grid_endpts - Integer Array, of size 2 x Ndim, of the two end-points' coordinates of the LOCAL task grid. It is implicitly assumed to be declared like task_Grid_endpts[ 2 ][ Ndim ].
returned value - returns MPI_SUCCESS if completed successfully

Notes on Fortran Interface

The RGX routines which have this message have a Fortran interface. If the C function that is defined here has a returned integer status, the Fortran interface will have an additional argument, ierr, at the end of its argument list.

Notes on Minimal Set of Variables

In order to use RGX for a regualr grid calculation. There is a minimal set of variables needed to be used with the RGX_XXX routines. The set of variables is listed as follows,


   const int     MD_type = MPI_DOUBLE_PRECISION;
   double       *Task_xGrid;         // Data of Local Task Grid              
   int           Ndim;               // Dimensionality of the 
   //                                // grid           
   MPI_Comm      RGX_Comm;           // Communicator of all 
   //                                // sub-grids        
   int           N_task;             // No. of process/tasks 
   //                                // in Communicator 
   int          *Glb_Grid_sz;        // Global grid sizes :
   //                                // Glb_Grid_sz(Ndim) 
   int          *task_Ngbrs;         // the tid of the nearest
   //                                // neighbor task :
   //                                // task_Ngbrs(2, Ndim)                
   int          *task_Grid_endpts;   // local sub-grid's end
   //                                // points :
   //                                // task_Grid_endpts(Ndim, 2)          
   int          *N_task_1dims;       // No of task 
   //                                // per dimension :             
   //                                // N_task_1dims(Ndim)                 
   int          *stride_width;       // width of the stride of
   //                                // ghost point :
   //                                // stride_width(Ndim)                 
   MPI_Datatype *task_bndry_strides; // local task/grid's 
   //                                // boundary strides :
   //                                // task_bndry_strides(Ndim)           

Memory for each of these pointer variables can be allocated dynammically/statically, but it has to be continuous.

Supported Data Type of the Block Array

There are currently 5 datatypes supported in RGX. The types are identified by MPI_Datatype. They are MPI_INTEGER, MPI_REAL, MPI_DOUBLE_PRECISION, MPI_COMPLEX and MPI_DOUBLE_COMPLEX.

Definition Location

This subroutine is defined in the librgx.a.

Location:../src/librgx/RGX_Find_Task_Grid_endpts.c