psb_cdbldext -- Build an extended communication descriptor

call psb_cdbldext(a,desc_a,nl,desc_out, info, extype)

This subroutine builds an extended communication descriptor, based on the input descriptor desc_a and on the stencil specified through the input sparse matrix a.

Type:

Synchronous.

On Entry

a

A sparse matrix Scope:local.
Type:required.
Intent: in.
Specified as: a structured data type.

desc_a

the communication descriptor.
Scope:local.
Type:required.
Intent: in.
Specified as: a structured data of type spdatapsb_Tspmat_type.

nl

the number of additional layers desired.
Scope:global.
Type:required.
Intent: in.
Specified as: an integer value $nl\ge 0$.

extype

the kind of estension required.
Scope:global.
Type:optional .
Intent: in.
Specified as: an integer value psb_ovt_xhal_, psb_ovt_asov_, default: psb_ovt_xhal_

On Return

desc_out

the extended communication descriptor.
Scope:local.
Type:required.
Intent: inout.
Specified as: a structured data of type descdatapsb_desc_type.

info

Error code.
Scope: local
Type: required
Intent: out.
An integer value; 0 means no error has been detected.

Notes

1. Specifying psb_ovt_xhal_ for the extype argument the user will obtain a descriptor for a domain partition in which the additional layers are fetched as part of an (extended) halo; however the index-to-process mapping is identical to that of the base descriptor;
2. Specifying psb_ovt_asov_ for the extype argument the user will obtain a descriptor with an overlapped decomposition: the additional layer is aggregated to the local subdomain (and thus is an overlap), and a new halo extending beyond the last additional layer is formed.