NAG Library Routine Document

f06guf  (zgthr)

 Contents

    1  Purpose
    7  Accuracy
    10  Example

1
Purpose

f06guf (zgthr) gathers specified (usually nonzero) elements of a complex vector y in full storage form into a sparse complex vector x in compressed form.

2
Specification

Fortran Interface
Subroutine f06guf ( nz, y, x, indx)
Integer, Intent (In):: nz, indx(*)
Complex (Kind=nag_wp), Intent (In):: y(*)
Complex (Kind=nag_wp), Intent (Inout):: x(*)
C Header Interface
#include nagmk26.h
void  f06guf_ ( const Integer *nz, const Complex y[], Complex x[], const Integer indx[])
The routine may be called by its BLAS name zgthr.

3
Description

None.

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:     y* – Complex (Kind=nag_wp) arrayInput
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.
3:     x* – Complex (Kind=nag_wp) arrayOutput
Note: the dimension of the array x must be at least max1,nz.
On exit: the compressed vector x.
4:     indx* – Integer arrayInput
Note: the dimension of the array indx must be at least max1,nz .
On entry: indx must contain the set of indices J.

6
Error Indicators and Warnings

None.

7
Accuracy

Not applicable.

8
Parallelism and Performance

f06guf (zgthr) is not threaded in any implementation.

9
Further Comments

None.

10
Example

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