dbcsr_t_pgrid_create_expert Subroutine

public subroutine dbcsr_t_pgrid_create_expert(mp_comm, dims, pgrid, map1_2d, map2_2d, tensor_dims, nsplit, dimsplit)

Create an n-dimensional process grid. We can not use a n-dimensional MPI cartesian grid for tensors since the mapping between n-dim. and 2-dim. index allows for an arbitrary reordering of tensor index. Therefore we can not use n-dim. MPI Cartesian grid because it may not be consistent with the respective 2d grid. The 2d Cartesian MPI grid is the reference grid (since tensor data is stored as DBCSR matrix) and this routine creates an object that is a n-dim. interface to this grid. map1_2d and map2_2d don't need to be specified (correctly), grid may be redefined in dbcsr_t_distribution_new Note that pgrid is equivalent to a MPI cartesian grid only if map1_2d and map2_2d don't reorder indices (which is the case if [map1_2d, map2_2d] == [1, 2, ..., ndims]). Otherwise the mapping of grid coordinates to processes depends on the ordering of the indices and is not equivalent to a MPI cartesian grid.

Arguments

Type	Intent	Optional	Attributes		Name
type(mp_comm_type),	intent(in)			::	mp_comm	simple MPI Communicator
integer,	intent(inout),		DIMENSION(:)	::	dims	grid dimensions - if entries are 0, dimensions are chosen automatically.
type(dbcsr_t_pgrid_type),	intent(out)			::	pgrid	n-dimensional grid object
integer,	intent(in),		DIMENSION(:)	::	map1_2d	which nd-indices map to first matrix index and in which order which nd-indices map to first matrix index and in which order
integer,	intent(in),		DIMENSION(:)	::	map2_2d	which nd-indices map to first matrix index and in which order which nd-indices map to first matrix index and in which order
integer,	intent(in),	optional,	DIMENSION(:)	::	tensor_dims	tensor block dimensions. If present, process grid dimensions are created such that good load balancing is ensured even if some of the tensor dimensions are small (i.e. on the same order or smaller than nproc**(1/ndim) where ndim is the tensor rank)
integer,	intent(in),	optional		::	nsplit	impose a constant split factor which matrix dimension to split
integer,	intent(in),	optional		::	dimsplit	impose a constant split factor which matrix dimension to split