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 Arguments

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

Background information to multithreading can be found in the Multithreading documentation.

a02acf is not threaded in any implementation.

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)

a02ac: FL CL CPP AD PY MB

NAG FL Interfacea02acf (divide)

▸▿ Contents

1 Purpose

2 Specification

3 Description

4 References

5 Arguments

6 Error Indicators and Warnings

7 Accuracy

8 Parallelism and Performance

9 Further Comments

10 Example

10.1 Program Text

10.2 Program Data

10.3 Program Results

NAG FL Interface
a02acf (divide)