dget06.f

来自「famous linear algebra library (LAPACK) p」· F 代码 · 共 66 行

      DOUBLE PRECISION FUNCTION DGET06( RCOND, RCONDC )
*
*  -- LAPACK test routine (version 3.1) --
*     Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd..
*     November 2006
*
*     .. Scalar Arguments ..
      DOUBLE PRECISION   RCOND, RCONDC
*     ..
*
*  Purpose
*  =======
*
*  DGET06 computes a test ratio to compare two values for RCOND.
*
*  Arguments
*  ==========
*
*  RCOND   (input) DOUBLE PRECISION
*          The estimate of the reciprocal of the condition number of A,
*          as computed by DGECON.
*
*  RCONDC  (input) DOUBLE PRECISION
*          The reciprocal of the condition number of A, computed as
*          ( 1/norm(A) ) / norm(inv(A)).
*
*  =====================================================================
*
*     .. Parameters ..
      DOUBLE PRECISION   ZERO, ONE
      PARAMETER          ( ZERO = 0.0D+0, ONE = 1.0D+0 )
*     ..
*     .. Local Scalars ..
      DOUBLE PRECISION   EPS, RAT
*     ..
*     .. External Functions ..
      DOUBLE PRECISION   DLAMCH
      EXTERNAL           DLAMCH
*     ..
*     .. Intrinsic Functions ..
      INTRINSIC          MAX, MIN
*     ..
*     .. Executable Statements ..
*
      EPS = DLAMCH( 'Epsilon' )
      IF( RCOND.GT.ZERO ) THEN
         IF( RCONDC.GT.ZERO ) THEN
            RAT = MAX( RCOND, RCONDC ) / MIN( RCOND, RCONDC ) -
     $            ( ONE-EPS )
         ELSE
            RAT = RCOND / EPS
         END IF
      ELSE
         IF( RCONDC.GT.ZERO ) THEN
            RAT = RCONDC / EPS
         ELSE
            RAT = ZERO
         END IF
      END IF
      DGET06 = RAT
      RETURN
*
*     End of DGET06
*
      END