F06GTF (ZAXPYI) (PDF version)
F06 Chapter Contents
F06 Chapter Introduction
NAG Library Manual

# NAG Library Routine DocumentF06GTF (ZAXPYI)

Note:  before using this routine, please read the Users' Note for your implementation to check the interpretation of bold italicised terms and other implementation-dependent details.

## 1  Purpose

F06GTF (ZAXPYI) adds a scaled sparse complex vector to an unscaled complex vector.

## 2  Specification

 SUBROUTINE F06GTF ( NZ, A, X, INDX, Y)
 INTEGER NZ, INDX(*) COMPLEX (KIND=nag_wp) A, X(*), Y(*)
The routine may be called by its BLAS name zaxpyi.

## 3  Description

F06GTF (ZAXPYI) performs the operation
 $y←αx+y$
where $x$ is a sparse complex vector stored in compressed form, and $y$ is a complex vector in full storage form.
Dodson D S, Grimes R G and Lewis J G (1991) Sparse extensions to the Fortran basic linear algebra subprograms ACM Trans. Math. Software 17 253–263

## 5  Parameters

1:     $\mathrm{NZ}$ – INTEGERInput
On entry: the number of nonzeros in the sparse vector $x$.
2:     $\mathrm{A}$ – COMPLEX (KIND=nag_wp)Input
On entry: the scalar $\alpha$.
3:     $\mathrm{X}\left(*\right)$ – COMPLEX (KIND=nag_wp) arrayInput
Note: the dimension of the array X must be at least $\mathrm{max}\phantom{\rule{0.125em}{0ex}}\left(1,{\mathbf{NZ}}\right)$.
On entry: the compressed vector $x$. X contains ${x}_{i}$ for $i\in J$.
4:     $\mathrm{INDX}\left(*\right)$ – INTEGER arrayInput
Note: the dimension of the array INDX must be at least $\mathrm{max}\phantom{\rule{0.125em}{0ex}}\left(1,{\mathbf{NZ}}\right)$.
On entry: the indices of the elements in the compressed vector $x$.
Constraint: the indices must be distinct.
5:     $\mathrm{Y}\left(*\right)$ – COMPLEX (KIND=nag_wp) arrayInput/Output
Note: the dimension of the array Y must be at least $\underset{\mathit{k}}{\mathrm{max}}\phantom{\rule{0.25em}{0ex}}\left\{{\mathbf{INDX}}\left(\mathit{k}\right)\right\}$.
On entry: the vector $y$. Only elements corresponding to indices in INDX are accessed.
On exit: the updated vector $y$.

None.

Not applicable.

Not applicable.

None.

## 10  Example

None.

F06GTF (ZAXPYI) (PDF version)
F06 Chapter Contents
F06 Chapter Introduction
NAG Library Manual