psb_genrm2 -- 2-Norm of Vector

This function computes the 2-norm of a vector $x$.
If $x$ is a double precision real vector it computes 2-norm as:

$$nrm2 \leftarrow \sqrt{x^T x}$$

else if $x$ is double precision complex vector then it computes 2-norm as:

$$nrm2 \leftarrow \sqrt{x^H x}$$

Table 8: Data types

$nrm2$	$x$	Function
Short Precision Real	Short Precision Real	psb_genrm2
Long Precision Real	Long Precision Real	psb_genrm2
Short Precision Real	Short Precision Complex	psb_genrm2
Long Precision Real	Long Precision Complex	psb_genrm2

psb_genrm2(x, desc_a, info)

Type:

Synchronous.

On Entry

x

the local portion of global dense matrix $x$.
Scope: local
Type: required
Intent: in.
Specified as: a rank one or two array containing numbers of type specified in Table 8.

desc_a

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

On Return

Function Value

is the 2-norm of subvector $x$.
Scope: global
Type: required
Specified as: a long precision real number.

info

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