NAG Library Routine Document

f06gtf  (zaxpyi)

 Contents

    1  Purpose
    7  Accuracy
    10  Example

1
Purpose

f06gtf (zaxpyi) adds a scaled sparse complex vector to an unscaled complex vector.

2
Specification

Fortran Interface
Subroutine f06gtf ( nz, a, x, indx, y)
Integer, Intent (In):: nz, indx(*)
Complex (Kind=nag_wp), Intent (In):: a, x(*)
Complex (Kind=nag_wp), Intent (Inout):: y(*)
C Header Interface
#include nagmk26.h
void  f06gtf_ ( const Integer *nz, const Complex *a, const Complex x[], const Integer indx[], Complex y[])
The routine may be called by its BLAS name zaxpyi.

3
Description

f06gtf (zaxpyi) performs the operation
yαx+y  
where x is a sparse complex vector stored in compressed form, and y is a complex vector in full storage form.

4
References

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
Arguments

1:     nz – IntegerInput
On entry: the number of nonzeros in the sparse vector x.
2:     a – Complex (Kind=nag_wp)Input
On entry: the scalar α.
3:     x* – Complex (Kind=nag_wp) arrayInput
Note: the dimension of the array x must be at least max1,nz .
On entry: the compressed vector x. x contains xi for iJ.
4:     indx* – Integer arrayInput
Note: the dimension of the array indx must be at least max1,nz .
On entry: the indices of the elements in the compressed vector x.
Constraint: the indices must be distinct.
5:     y* – Complex (Kind=nag_wp) arrayInput/Output
Note: the dimension of the array y must be at least maxkindxk .
On entry: the vector y. Only elements corresponding to indices in indx are accessed.
On exit: the updated vector y.

6
Error Indicators and Warnings

None.

7
Accuracy

Not applicable.

8
Parallelism and Performance

f06gtf (zaxpyi) is not threaded in any implementation.

9
Further Comments

None.

10
Example

None.
© The Numerical Algorithms Group Ltd, Oxford, UK. 2017