view libcruft/lapack/dladiv.f @ 6469:a848b846cb3a ss-2-9-10

[project @ 2007-03-27 18:42:11 by jwe]
author jwe
date Tue, 27 Mar 2007 18:42:11 +0000
parents 15cddaacbc2d
children 68db500cb558
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      SUBROUTINE DLADIV( A, B, C, D, P, Q )
*
*  -- LAPACK auxiliary routine (version 3.0) --
*     Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd.,
*     Courant Institute, Argonne National Lab, and Rice University
*     October 31, 1992
*
*     .. Scalar Arguments ..
      DOUBLE PRECISION   A, B, C, D, P, Q
*     ..
*
*  Purpose
*  =======
*
*  DLADIV 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) DOUBLE PRECISION
*  B       (input) DOUBLE PRECISION
*  C       (input) DOUBLE PRECISION
*  D       (input) DOUBLE PRECISION
*          The scalars a, b, c, and d in the above expression.
*
*  P       (output) DOUBLE PRECISION
*  Q       (output) DOUBLE PRECISION
*          The scalars p and q in the above expression.
*
*  =====================================================================
*
*     .. Local Scalars ..
      DOUBLE PRECISION   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 DLADIV
*
      END