NAG Library Routine Document

f06taf  (zsymv)

 Contents

    1  Purpose
    7  Accuracy
    10  Example

1
Purpose

f06taf performs the matrix-vector operation
yαAx + βy,  
where A is an n by n complex symmetric matrix, x and y are n-element complex vectors, and α and β are complex scalars.

2
Specification

Fortran Interface
Subroutine f06taf ( uplo, n, alpha, a, lda, x, incx, beta, y, incy)
Integer, Intent (In):: n, lda, incx, incy
Complex (Kind=nag_wp), Intent (In):: alpha, a(lda,*), x(*), beta
Complex (Kind=nag_wp), Intent (Inout):: y(*)
Character (1), Intent (In):: uplo
C Header Interface
#include nagmk26.h
void  f06taf_ ( const char *uplo, const Integer *n, const Complex *alpha, const Complex a[], const Integer *lda, const Complex x[], const Integer *incx, const Complex *beta, Complex y[], const Integer *incy, const Charlen length_uplo)

3
Description

None.

4
References

None.

5
Arguments

1:     uplo – Character(1)Input
On entry: specifies whether the upper or lower triangular part of A is stored.
uplo='U'
The upper triangular part of A is stored.
uplo='L'
The lower triangular part of A is stored.
Constraint: uplo='U' or 'L'.
2:     n – IntegerInput
On entry: n, the order of the matrix A.
Constraint: n0.
3:     alpha – Complex (Kind=nag_wp)Input
On entry: the scalar α.
4:     alda* – Complex (Kind=nag_wp) arrayInput
Note: the second dimension of the array a must be at least max1,n.
On entry: the n by n symmetric matrix A.
  • If uplo='U', the upper triangular part of A must be stored and the elements of the array below the diagonal are not referenced.
  • If uplo='L', the lower triangular part of A must be stored and the elements of the array above the diagonal are not referenced.
5:     lda – IntegerInput
On entry: the first dimension of the array a as declared in the (sub)program from which f06taf is called.
Constraint: lda max1,n .
6:     x* – Complex (Kind=nag_wp) arrayInput
Note: the dimension of the array x must be at least max1, 1+n-1 ×incx .
On entry: the n-element vector x.
If incx>0, xi must be stored in x1+i-1×incx, for i=1,2,,n.
If incx<0, xi must be stored in x1-n-i×incx, for i=1,2,,n.
Intermediate elements of x are not referenced.
7:     incx – IntegerInput
On entry: the increment in the subscripts of x between successive elements of x.
Constraint: incx0.
8:     beta – Complex (Kind=nag_wp)Input
On entry: the scalar β.
9:     y* – Complex (Kind=nag_wp) arrayInput/Output
Note: the dimension of the array y must be at least max1, 1+n-1 ×incy .
On entry: the n-element vector y.
If incy>0, yi must be stored in y1+i1×incy , for i=1,2,,n.
If incy<0, yi must be stored in y1ni×incy , for i=1,2,,n.
On exit: the updated vector y stored in the array elements used to supply the original vector y.
10:   incy – IntegerInput
On entry: the increment in the subscripts of y between successive elements of y.
Constraint: incy0.

6
Error Indicators and Warnings

None.

7
Accuracy

Not applicable.

8
Parallelism and Performance

f06taf is not threaded in any implementation.

9
Further Comments

None.

10
Example

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