F06KCF (PDF version)
F06 Chapter Contents
F06 Chapter Introduction
NAG Library Manual

NAG Library Routine Document

F06KCF

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.

 Contents

    1  Purpose
    7  Accuracy
    10  Example

1  Purpose

F06KCF multiplies a complex vector by a real diagonal matrix.

2  Specification

SUBROUTINE F06KCF ( N, D, INCD, X, INCX)
INTEGER  N, INCD, INCX
REAL (KIND=nag_wp)  D(*)
COMPLEX (KIND=nag_wp)  X(*)

3  Description

F06KCF performs the operation
xDx  
where x is an n-element complex vector and D=diagd is a real diagonal matrix.
Equivalently, the routine performs the element-by-element product of the vectors x and d 
xi=dixi,  i=1,2,,n.  

4  References

None.

5  Parameters

1:     N – INTEGERInput
On entry: n, the number of elements in d and x.
2:     D* – REAL (KIND=nag_wp) arrayInput
Note: the dimension of the array D must be at least max1, 1+N-1 ×INCD .
On entry: the vector d.
If INCD>0, di must be stored in Di-1×INCD+1 , for i=1,2,,N.
If INCD<0, di must be stored in D 1-N-i×INCD , for i=1,2,,N.
3:     INCD – INTEGERInput
On entry: the increment in the subscripts of D between successive elements of d.
4:     X* – COMPLEX (KIND=nag_wp) arrayInput/Output
Note: the dimension of the array X must be at least max1, 1+N-1 ×INCX .
On entry: the array X must contain the n-element vector x.
If INCX>0, xi must be stored in X 1+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.
On exit: the updated vector x stored in the array elements used to supply the original vector x.
Intermediate elements of X are unchanged.
5:     INCX – INTEGERInput
On entry: the increment in the subscripts of X between successive elements of x.

6  Error Indicators and Warnings

None.

7  Accuracy

Not applicable.

8  Parallelism and Performance

F06KCF is not threaded by NAG in any implementation.
F06KCF makes calls to BLAS and/or LAPACK routines, which may be threaded within the vendor library used by this implementation. Consult the documentation for the vendor library for further information.
Please consult the X06 Chapter Introduction for information on how to control and interrogate the OpenMP environment used within this routine. Please also consult the Users' Note for your implementation for any additional implementation-specific information.

9  Further Comments

None.

10  Example

None.

F06KCF (PDF version)
F06 Chapter Contents
F06 Chapter Introduction
NAG Library Manual

© The Numerical Algorithms Group Ltd, Oxford, UK. 2015