NAG Library Routine Document

A02ACF

is calculated using Smith's algorithm with scaling, from Li et al. (2002), which ensures that no unnecessary overflow or underflow occurs at intermediate stages of the computation.

4 References

Li X S, Demmel J W, Bailey D H, Henry G, Hida Y, Iskandar J, Kahan W, Kapur A, Martin M C, Tung T and Yoo D J (2002) Design, implementation and testing of extended and mixed precision BLAS ACM Trans. Math. Soft. 28(2) 152–205

5 Parameters

1: $XR$ – REAL (KIND=nag_wp)Input
2: $XI$ – REAL (KIND=nag_wp)Input: On entry: $x_{r}$ and $x_{i}$ , the real and imaginary parts of $x$ , respectively.
3: $YR$ – REAL (KIND=nag_wp)Input
4: $YI$ – REAL (KIND=nag_wp)Input: On entry: $y_{r}$ and $y_{i}$ , the real and imaginary parts of $y$ , respectively.
5: $ZR$ – REAL (KIND=nag_wp)Output
6: $ZI$ – REAL (KIND=nag_wp)Output: On exit: $z_{r}$ and $z_{i}$ , the real and imaginary parts of $z$ , respectively.

6 Error Indicators and Warnings

None.

7 Accuracy

The result should be correct to machine precision.

8 Parallelism and Performance

Not applicable.

9 Further Comments

The time taken by A02ACF is negligible.

This routine must not be called with

YR = 0.0

and

YI = 0.0

10 Example

This example finds the value of

(- 1.7 + 2.6 i) / (- 3.1 - 0.9 i)

NAG Library Routine DocumentA02ACF

▸▿ Contents

1 Purpose

2 Specification

3 Description