194 lines
5.2 KiB
Fortran
194 lines
5.2 KiB
Fortran
*> \brief \b DLAMCH
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*
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* =========== DOCUMENTATION ===========
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*
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* Online html documentation available at
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* http://www.netlib.org/lapack/explore-html/
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*
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* Definition:
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* ===========
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*
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* DOUBLE PRECISION FUNCTION DLAMCH( CMACH )
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*
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*
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*> \par Purpose:
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* =============
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*>
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*> \verbatim
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*>
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*> DLAMCH determines double precision machine parameters.
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*> \endverbatim
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*
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* Arguments:
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* ==========
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*
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*> \param[in] CMACH
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*> \verbatim
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*> Specifies the value to be returned by DLAMCH:
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*> = 'E' or 'e', DLAMCH := eps
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*> = 'S' or 's , DLAMCH := sfmin
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*> = 'B' or 'b', DLAMCH := base
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*> = 'P' or 'p', DLAMCH := eps*base
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*> = 'N' or 'n', DLAMCH := t
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*> = 'R' or 'r', DLAMCH := rnd
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*> = 'M' or 'm', DLAMCH := emin
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*> = 'U' or 'u', DLAMCH := rmin
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*> = 'L' or 'l', DLAMCH := emax
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*> = 'O' or 'o', DLAMCH := rmax
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*> where
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*> eps = relative machine precision
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*> sfmin = safe minimum, such that 1/sfmin does not overflow
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*> base = base of the machine
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*> prec = eps*base
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*> t = number of (base) digits in the mantissa
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*> rnd = 1.0 when rounding occurs in addition, 0.0 otherwise
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*> emin = minimum exponent before (gradual) underflow
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*> rmin = underflow threshold - base**(emin-1)
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*> emax = largest exponent before overflow
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*> rmax = overflow threshold - (base**emax)*(1-eps)
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*> \endverbatim
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*
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* Authors:
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* ========
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*
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*> \author Univ. of Tennessee
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*> \author Univ. of California Berkeley
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*> \author Univ. of Colorado Denver
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*> \author NAG Ltd.
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*
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*> \date November 2011
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*
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*> \ingroup auxOTHERauxiliary
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*
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* =====================================================================
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DOUBLE PRECISION FUNCTION DLAMCH( CMACH )
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*
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* -- LAPACK auxiliary routine (version 3.4.0) --
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* -- LAPACK is a software package provided by Univ. of Tennessee, --
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* -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
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* November 2011
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*
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* .. Scalar Arguments ..
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CHARACTER CMACH
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* ..
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*
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* .. Scalar Arguments ..
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DOUBLE PRECISION A, B
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* ..
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*
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* =====================================================================
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*
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* .. Parameters ..
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DOUBLE PRECISION ONE, ZERO
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PARAMETER ( ONE = 1.0D+0, ZERO = 0.0D+0 )
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* ..
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* .. Local Scalars ..
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DOUBLE PRECISION RND, EPS, SFMIN, SMALL, RMACH
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* ..
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* .. External Functions ..
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LOGICAL LSAME
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EXTERNAL LSAME
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* ..
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* .. Intrinsic Functions ..
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INTRINSIC DIGITS, EPSILON, HUGE, MAXEXPONENT,
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$ MINEXPONENT, RADIX, TINY
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* ..
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* .. Executable Statements ..
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*
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*
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* Assume rounding, not chopping. Always.
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*
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RND = ONE
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*
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IF( ONE.EQ.RND ) THEN
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EPS = EPSILON(ZERO) * 0.5
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ELSE
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EPS = EPSILON(ZERO)
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END IF
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*
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IF( LSAME( CMACH, 'E' ) ) THEN
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RMACH = EPS
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ELSE IF( LSAME( CMACH, 'S' ) ) THEN
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SFMIN = TINY(ZERO)
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SMALL = ONE / HUGE(ZERO)
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IF( SMALL.GE.SFMIN ) THEN
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*
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* Use SMALL plus a bit, to avoid the possibility of rounding
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* causing overflow when computing 1/sfmin.
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*
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SFMIN = SMALL*( ONE+EPS )
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END IF
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RMACH = SFMIN
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ELSE IF( LSAME( CMACH, 'B' ) ) THEN
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RMACH = RADIX(ZERO)
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ELSE IF( LSAME( CMACH, 'P' ) ) THEN
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RMACH = EPS * RADIX(ZERO)
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ELSE IF( LSAME( CMACH, 'N' ) ) THEN
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RMACH = DIGITS(ZERO)
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ELSE IF( LSAME( CMACH, 'R' ) ) THEN
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RMACH = RND
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ELSE IF( LSAME( CMACH, 'M' ) ) THEN
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RMACH = MINEXPONENT(ZERO)
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ELSE IF( LSAME( CMACH, 'U' ) ) THEN
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RMACH = tiny(zero)
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ELSE IF( LSAME( CMACH, 'L' ) ) THEN
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RMACH = MAXEXPONENT(ZERO)
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ELSE IF( LSAME( CMACH, 'O' ) ) THEN
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RMACH = HUGE(ZERO)
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ELSE
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RMACH = ZERO
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END IF
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*
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DLAMCH = RMACH
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RETURN
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*
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* End of DLAMCH
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*
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END
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************************************************************************
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*> \brief \b DLAMC3
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*> \details
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*> \b Purpose:
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*> \verbatim
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*> DLAMC3 is intended to force A and B to be stored prior to doing
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*> the addition of A and B , for use in situations where optimizers
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*> might hold one of these in a register.
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*> \endverbatim
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*> \author LAPACK is a software package provided by Univ. of Tennessee, Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..
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*> \date November 2011
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*> \ingroup auxOTHERauxiliary
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*>
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*> \param[in] A
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*> \verbatim
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*> A is a DOUBLE PRECISION
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*> \endverbatim
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*>
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*> \param[in] B
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*> \verbatim
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*> B is a DOUBLE PRECISION
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*> The values A and B.
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*> \endverbatim
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*>
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DOUBLE PRECISION FUNCTION DLAMC3( A, B )
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*
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* -- LAPACK auxiliary routine (version 3.4.0) --
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* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd..
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* November 2010
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*
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* .. Scalar Arguments ..
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DOUBLE PRECISION A, B
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* ..
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* =====================================================================
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*
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* .. Executable Statements ..
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*
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DLAMC3 = A + B
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*
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RETURN
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*
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* End of DLAMC3
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*
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END
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*
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************************************************************************
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