view libcruft/lapack/sladiv.f @ 7789:82be108cc558

First attempt at single precision tyeps * * * corrections to qrupdate single precision routines * * * prefer demotion to single over promotion to double * * * Add single precision support to log2 function * * * Trivial PROJECT file update * * * Cache optimized hermitian/transpose methods * * * Add tests for tranpose/hermitian and ChangeLog entry for new transpose code
author David Bateman <dbateman@free.fr>
date Sun, 27 Apr 2008 22:34:17 +0200
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      SUBROUTINE SLADIV( A, B, C, D, P, Q )
*
*  -- LAPACK auxiliary routine (version 3.1) --
*     Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd..
*     November 2006
*
*     .. Scalar Arguments ..
      REAL               A, B, C, D, P, Q
*     ..
*
*  Purpose
*  =======
*
*  SLADIV performs complex division in  real arithmetic
*
*                        a + i*b
*             p + i*q = ---------
*                        c + i*d
*
*  The algorithm is due to Robert L. Smith and can be found
*  in D. Knuth, The art of Computer Programming, Vol.2, p.195
*
*  Arguments
*  =========
*
*  A       (input) REAL
*  B       (input) REAL
*  C       (input) REAL
*  D       (input) REAL
*          The scalars a, b, c, and d in the above expression.
*
*  P       (output) REAL
*  Q       (output) REAL
*          The scalars p and q in the above expression.
*
*  =====================================================================
*
*     .. Local Scalars ..
      REAL               E, F
*     ..
*     .. Intrinsic Functions ..
      INTRINSIC          ABS
*     ..
*     .. Executable Statements ..
*
      IF( ABS( D ).LT.ABS( C ) ) THEN
         E = D / C
         F = C + D*E
         P = ( A+B*E ) / F
         Q = ( B-A*E ) / F
      ELSE
         E = C / D
         F = D + C*E
         P = ( B+A*E ) / F
         Q = ( -A+B*E ) / F
      END IF
*
      RETURN
*
*     End of SLADIV
*
      END