Go to the documentation of this file.
00001 *> \brief \b DLAMCH
00002 *
00003 *  =========== DOCUMENTATION ===========
00004 *
00005 * Online html documentation available at 
00006 *            http://www.netlib.org/lapack/explore-html/ 
00007 *
00008 *  Definition:
00009 *  ===========
00010 *
00011 *      DOUBLE PRECISION FUNCTION DLAMCH( CMACH )
00012 *  
00013 *
00014 *> \par Purpose:
00015 *  =============
00016 *>
00017 *> \verbatim
00018 *>
00019 *> DLAMCH determines double precision machine parameters.
00020 *> \endverbatim
00021 *
00022 *  Arguments:
00023 *  ==========
00024 *
00025 *> \param[in] CMACH
00026 *> \verbatim
00027 *>          Specifies the value to be returned by DLAMCH:
00028 *>          = 'E' or 'e',   DLAMCH := eps
00029 *>          = 'S' or 's ,   DLAMCH := sfmin
00030 *>          = 'B' or 'b',   DLAMCH := base
00031 *>          = 'P' or 'p',   DLAMCH := eps*base
00032 *>          = 'N' or 'n',   DLAMCH := t
00033 *>          = 'R' or 'r',   DLAMCH := rnd
00034 *>          = 'M' or 'm',   DLAMCH := emin
00035 *>          = 'U' or 'u',   DLAMCH := rmin
00036 *>          = 'L' or 'l',   DLAMCH := emax
00037 *>          = 'O' or 'o',   DLAMCH := rmax
00038 *>          where
00039 *>          eps   = relative machine precision
00040 *>          sfmin = safe minimum, such that 1/sfmin does not overflow
00041 *>          base  = base of the machine
00042 *>          prec  = eps*base
00043 *>          t     = number of (base) digits in the mantissa
00044 *>          rnd   = 1.0 when rounding occurs in addition, 0.0 otherwise
00045 *>          emin  = minimum exponent before (gradual) underflow
00046 *>          rmin  = underflow threshold - base**(emin-1)
00047 *>          emax  = largest exponent before overflow
00048 *>          rmax  = overflow threshold  - (base**emax)*(1-eps)
00049 *> \endverbatim
00050 *
00051 *  Authors:
00052 *  ========
00053 *
00054 *> \author Univ. of Tennessee 
00055 *> \author Univ. of California Berkeley 
00056 *> \author Univ. of Colorado Denver 
00057 *> \author NAG Ltd. 
00058 *
00059 *> \date November 2011
00060 *
00061 *> \ingroup auxOTHERauxiliary
00062 *
00063 *  =====================================================================
00064       DOUBLE PRECISION FUNCTION DLAMCH( CMACH )
00065 *
00066 *  -- LAPACK auxiliary routine (version 3.4.0) --
00067 *  -- LAPACK is a software package provided by Univ. of Tennessee,    --
00068 *  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
00069 *     November 2011
00070 *
00071 *     .. Scalar Arguments ..
00072       CHARACTER          CMACH
00073 *     ..
00074 *
00075 *     .. Scalar Arguments ..
00076       DOUBLE PRECISION   A, B
00077 *     ..
00078 *
00079 * =====================================================================
00080 *
00081 *     .. Parameters ..
00082       DOUBLE PRECISION   ONE, ZERO
00083       PARAMETER          ( ONE = 1.0D+0, ZERO = 0.0D+0 )
00084 *     ..
00085 *     .. Local Scalars ..
00086       DOUBLE PRECISION   RND, EPS, SFMIN, SMALL, RMACH
00087 *     ..
00088 *     .. External Functions ..
00089       LOGICAL            LSAME
00090       EXTERNAL           LSAME
00091 *     ..
00092 *     .. Intrinsic Functions ..
00093       INTRINSIC          DIGITS, EPSILON, HUGE, MAXEXPONENT,
00094      $                   MINEXPONENT, RADIX, TINY
00095 *     ..
00096 *     .. Executable Statements ..
00097 *
00098 *
00099 *     Assume rounding, not chopping. Always.
00100 *
00101       RND = ONE
00102 *
00103       IF( ONE.EQ.RND ) THEN
00104          EPS = EPSILON(ZERO) * 0.5
00105       ELSE
00106          EPS = EPSILON(ZERO)
00107       END IF
00108 *
00109       IF( LSAME( CMACH, 'E' ) ) THEN
00110          RMACH = EPS
00111       ELSE IF( LSAME( CMACH, 'S' ) ) THEN
00112          SFMIN = TINY(ZERO)
00113          SMALL = ONE / HUGE(ZERO)
00114          IF( SMALL.GE.SFMIN ) THEN
00115 *
00116 *           Use SMALL plus a bit, to avoid the possibility of rounding
00117 *           causing overflow when computing  1/sfmin.
00118 *
00119             SFMIN = SMALL*( ONE+EPS )
00120          END IF
00121          RMACH = SFMIN
00122       ELSE IF( LSAME( CMACH, 'B' ) ) THEN
00123          RMACH = RADIX(ZERO)
00124       ELSE IF( LSAME( CMACH, 'P' ) ) THEN
00125          RMACH = EPS * RADIX(ZERO)
00126       ELSE IF( LSAME( CMACH, 'N' ) ) THEN
00127          RMACH = DIGITS(ZERO)
00128       ELSE IF( LSAME( CMACH, 'R' ) ) THEN
00129          RMACH = RND
00130       ELSE IF( LSAME( CMACH, 'M' ) ) THEN
00131          RMACH = MINEXPONENT(ZERO)
00132       ELSE IF( LSAME( CMACH, 'U' ) ) THEN
00133          RMACH = tiny(zero)
00134       ELSE IF( LSAME( CMACH, 'L' ) ) THEN
00135          RMACH = MAXEXPONENT(ZERO)
00136       ELSE IF( LSAME( CMACH, 'O' ) ) THEN
00137          RMACH = HUGE(ZERO)
00138       ELSE
00139          RMACH = ZERO
00140       END IF
00141 *
00142       DLAMCH = RMACH
00143       RETURN
00144 *
00145 *     End of DLAMCH
00146 *
00147       END
00148 ************************************************************************
00149 *> \brief \b DLAMC3
00150 *> \details
00151 *> \b Purpose:
00152 *> \verbatim
00153 *> DLAMC3  is intended to force  A  and  B  to be stored prior to doing
00154 *> the addition of  A  and  B ,  for use in situations where optimizers
00155 *> might hold one of these in a register.
00156 *> \endverbatim
00157 *> \author LAPACK is a software package provided by Univ. of Tennessee, Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..
00158 *> \date November 2011
00159 *> \ingroup auxOTHERauxiliary
00160 *>
00161 *> \param[in] A
00162 *> \verbatim
00163 *>          A is a DOUBLE PRECISION
00164 *> \endverbatim
00165 *>
00166 *> \param[in] B
00167 *> \verbatim
00168 *>          B is a DOUBLE PRECISION
00169 *>          The values A and B.
00170 *> \endverbatim
00171 *>
00172       DOUBLE PRECISION FUNCTION DLAMC3( A, B )
00173 *
00174 *  -- LAPACK auxiliary routine (version 3.4.0) --
00175 *     Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd..
00176 *     November 2010
00177 *
00178 *     .. Scalar Arguments ..
00179       DOUBLE PRECISION   A, B
00180 *     ..
00181 * =====================================================================
00182 *
00183 *     .. Executable Statements ..
00184 *
00185       DLAMC3 = A + B
00186 *
00187       RETURN
00188 *
00189 *     End of DLAMC3
00190 *
00191       END
00192 *
00193 ************************************************************************