NAG FL Interface
f16ghf (zwaxpby)

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1 Purpose

f16ghf computes the sum of two scaled vectors, preserving input, for complex scalars and vectors.

2 Specification

Fortran Interface
Subroutine f16ghf ( n, alpha, x, incx, beta, y, incy, w, incw)
Integer, Intent (In) :: n, incx, incy, incw
Complex (Kind=nag_wp), Intent (In) :: alpha, x(1+(n-1)*ABS(incx)), beta, y(1+(n-1)*ABS(incy))
Complex (Kind=nag_wp), Intent (Inout) :: w(1+(n-1)*ABS(incw))
C Header Interface
#include <nag.h>
void  f16ghf_ (const Integer *n, const Complex *alpha, const Complex x[], const Integer *incx, const Complex *beta, const Complex y[], const Integer *incy, Complex w[], const Integer *incw)
The routine may be called by the names f16ghf, nagf_blast_zwaxpby or its BLAST name blas_zwaxpby.

3 Description

f16ghf performs the operation
w αx+βy,  
where x and y are n-element complex vectors, and α and β are complex scalars.

4 References

Basic Linear Algebra Subprograms Technical (BLAST) Forum (2001) Basic Linear Algebra Subprograms Technical (BLAST) Forum Standard University of Tennessee, Knoxville, Tennessee https://www.netlib.org/blas/blast-forum/blas-report.pdf

5 Arguments

1: n Integer Input
On entry: n, the number of elements in x, y and w.
2: alpha Complex (Kind=nag_wp) Input
On entry: the scalar α.
3: x(1+(n-1)×|incx|) Complex (Kind=nag_wp) array Input
On entry: the n-element vector x.
If incx>0, xi must be stored in x((i-1)×incx+1), for i=1,2,,n.
If incx<0, xi must be stored in x((n-i)×|incx|+1), for i=1,2,,n.
Intermediate elements of x are not referenced. If n=0, x is not referenced.
4: incx Integer Input
On entry: the increment in the subscripts of x between successive elements of x.
Constraint: incx0.
5: beta Complex (Kind=nag_wp) Input
On entry: the scalar β.
6: y(1+(n-1)×|incy|) Complex (Kind=nag_wp) array Input
On entry: the n-element vector y.
If incy>0, yi must be stored in y((i-1)×incy+1), for i=1,2,,n.
If incy<0, yi must be stored in y((n-i)×|incy|+1), for i=1,2,,n.
Intermediate elements of y are not referenced. If β=0.0 or n=0, y is not referenced.
7: incy Integer Input
On entry: the increment in the subscripts of y between successive elements of y.
Constraint: incy0.
8: w(1+(n-1)×|incw|) Complex (Kind=nag_wp) array Input/Output
On entry: if |incw|1, intermediate elements of w may contain values and will not be referenced; the other elements will be overwritten and need not be set.
On exit: the elements wi of the vector w will be stored in w as follows.
If incw>0, wi is in w((i-1)×incw+1), for i=1,2,,n.
If incw<0, wi is in w((n-i)×|incw|+1), for i=1,2,,n.
Intermediate elements of w are not referenced.
9: incw Integer Input
On entry: the increment in the subscripts of w between successive elements of w.
Constraint: incw0.

6 Error Indicators and Warnings

If incx=0 or incy=0 or incw=0, an error message is printed and program execution is terminated.

7 Accuracy

The BLAS standard requires accurate implementations which avoid unnecessary over/underflow (see Section 2.7 of Basic Linear Algebra Subprograms Technical (BLAST) Forum (2001)).

8 Parallelism and Performance

Background information to multithreading can be found in the Multithreading documentation.
f16ghf is not threaded in any implementation.

9 Further Comments

None.

10 Example

This example computes the result of a scaled vector accumulation for
α=3+2i,   x = (-6+1.2i,3.7+4.5i,-4+2.1i) T , β=-i,   y = (-5.1,6.4-5i,-3-2.4i) T .  
x and y, and also the sum vector w, are stored in reverse order.

10.1 Program Text

Program Text (f16ghfe.f90)

10.2 Program Data

Program Data (f16ghfe.d)

10.3 Program Results

Program Results (f16ghfe.r)