MA01DD

Approximate symmetric chordal metric for two finite complex numbers

[Specification] [Arguments] [Method] [References] [Comments] [Example]

Purpose

  To compute an approximate symmetric chordal metric for two complex
  numbers A1 and A2, with Aj = ARj + i*AIj, j = 1, 2.

Specification
      SUBROUTINE MA01DD( AR1, AI1, AR2, AI2, EPS, SAFEMN, D )
C     .. Scalar Arguments ..
      DOUBLE PRECISION  AI1, AI2, AR1, AR2, D, EPS, SAFEMN

Arguments

Input/Output Parameters

  AR1     (input) DOUBLE PRECISION
  AI1     (input) DOUBLE PRECISION
          These scalars define the real and imaginary parts of the
          number A1.

  AR2     (input) DOUBLE PRECISION
  AI2     (input) DOUBLE PRECISION
          These scalars define the real and imaginary parts of the
          number A2.

  EPS     (input) DOUBLE PRECISION
          The relative machine precision. See the LAPACK Library
          routine DLAMCH.

  SAFEMN  (input) DOUBLE PRECISION
          The "safe minimum", such that its reciprocal does not
          overflow. See the LAPACK Library routine DLAMCH.

  D       (output) DOUBLE PRECISION
          The approximate symmetric chordal metric D.  D >= 0.

Method
  The approximate symmetric chordal metric is evaluated using the
  formula

     D = MIN( | A1 - A2 |, |1/A1 - 1/A2| ).

  The chordal metric is finite even if A1 and A2 are both infinite,
  or if one of them is infinite and the other is finite, nonzero.

Further Comments
  None
Example

Program Text

  None
Program Data
  None
Program Results
  None

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