## psb_get_boundary -- Extract list of boundary elements

    call psb_get_boundary(bndel, desc, info)

Type:
  Asynchronous.
On Entry
desc
  the communication descriptor.
  Scope:local.
  Type:required.
  Intent: in.
  Specified as: a structured data of type descdata`psb_desc_type`.

On Return
bndel
  The list of boundary elements on the calling process, in local numbering.
  Scope: local
  Type: required
  Intent: out.
  Specified as: a rank one array with the ALLOCATABLE attribute, of type integer.
info
  Error code.
  Scope: local
  Type: required
  Intent: out.
  An integer value; 0 means no error has been detected.

Notes

1. If there are no boundary elements (i.e., if the local part of the connectivity graph is self-contained) the output vector is set to the “not allocated” state.
2. Otherwise the size of `bndel` will be exactly equal to the number of boundary elements.