psb_gather -- Gather Global Dense Matrix

These subroutines collect the portions of global dense matrix distributed over all process into one single array stored on one process.

$$glob\_x \leftarrow collect(loc\_x_i)$$

where:

$glob\_x$

is the global submatrix $glob\_x_{1:m,1:n}$

$loc\_x_i$

is the local portion of global dense matrix on process $i$.

$collect$

is the collect function.

Table 19: Data types

$x_i, y$	Subroutine
Integer	psb_gather
Short Precision Real	psb_gather
Long Precision Real	psb_gather
Short Precision Complex	psb_gather
Long Precision Complex	psb_gather

Type:

Synchronous.

On Entry

loc_x

the local portion of global dense matrix $glob\_x$.
Scope: local
Type: required
Intent: in.
Specified as: a rank one or two array or an object of type vdatapsb_T_vect_type indicated in Table 19.

desc_a

contains data structures for communications.
Scope: local
Type: required
Intent: in.
Specified as: a structured data of type descdatapsb_desc_type.

root

The process that holds the global copy. If $root=-1$ all the processes will have a copy of the global vector.
Scope: global
Type: optional
Intent: in.
Specified as: an integer variable $-1\le root\le np-1$, default $-1$.

On Return

glob_x

The array where the local parts must be gathered.
Scope: global
Type: required
Intent: out.
Specified as: a rank one or two array with the ALLOCATABLE attribute.

info

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