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    1: *> \brief \b DLAMCH
    2: *
    3: *  =========== DOCUMENTATION ===========
    4: *
    5: * Online html documentation available at 
    6: *            http://www.netlib.org/lapack/explore-html/ 
    7: *
    8: *  Definition:
    9: *  ===========
   10: *
   11: *      DOUBLE PRECISION FUNCTION DLAMCH( CMACH )
   12: *  
   13: *
   14: *> \par Purpose:
   15: *  =============
   16: *>
   17: *> \verbatim
   18: *>
   19: *> DLAMCH determines double precision machine parameters.
   20: *> \endverbatim
   21: *
   22: *  Arguments:
   23: *  ==========
   24: *
   25: *> \param[in] CMACH
   26: *> \verbatim
   27: *>          Specifies the value to be returned by DLAMCH:
   28: *>          = 'E' or 'e',   DLAMCH := eps
   29: *>          = 'S' or 's ,   DLAMCH := sfmin
   30: *>          = 'B' or 'b',   DLAMCH := base
   31: *>          = 'P' or 'p',   DLAMCH := eps*base
   32: *>          = 'N' or 'n',   DLAMCH := t
   33: *>          = 'R' or 'r',   DLAMCH := rnd
   34: *>          = 'M' or 'm',   DLAMCH := emin
   35: *>          = 'U' or 'u',   DLAMCH := rmin
   36: *>          = 'L' or 'l',   DLAMCH := emax
   37: *>          = 'O' or 'o',   DLAMCH := rmax
   38: *>          where
   39: *>          eps   = relative machine precision
   40: *>          sfmin = safe minimum, such that 1/sfmin does not overflow
   41: *>          base  = base of the machine
   42: *>          prec  = eps*base
   43: *>          t     = number of (base) digits in the mantissa
   44: *>          rnd   = 1.0 when rounding occurs in addition, 0.0 otherwise
   45: *>          emin  = minimum exponent before (gradual) underflow
   46: *>          rmin  = underflow threshold - base**(emin-1)
   47: *>          emax  = largest exponent before overflow
   48: *>          rmax  = overflow threshold  - (base**emax)*(1-eps)
   49: *> \endverbatim
   50: *
   51: *  Authors:
   52: *  ========
   53: *
   54: *> \author Univ. of Tennessee 
   55: *> \author Univ. of California Berkeley 
   56: *> \author Univ. of Colorado Denver 
   57: *> \author NAG Ltd. 
   58: *
   59: *> \date November 2011
   60: *
   61: *> \ingroup auxOTHERauxiliary
   62: *
   63: *  =====================================================================
   64:       DOUBLE PRECISION FUNCTION DLAMCH( CMACH )
   65: *
   66: *  -- LAPACK auxiliary routine (version 3.4.0) --
   67: *  -- LAPACK is a software package provided by Univ. of Tennessee,    --
   68: *  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
   69: *     November 2011
   70: *
   71: *     .. Scalar Arguments ..
   72:       CHARACTER          CMACH
   73: *     ..
   74: *
   75: *     .. Scalar Arguments ..
   76:       DOUBLE PRECISION   A, B
   77: *     ..
   78: *
   79: * =====================================================================
   80: *
   81: *     .. Parameters ..
   82:       DOUBLE PRECISION   ONE, ZERO
   83:       PARAMETER          ( ONE = 1.0D+0, ZERO = 0.0D+0 )
   84: *     ..
   85: *     .. Local Scalars ..
   86:       DOUBLE PRECISION   RND, EPS, SFMIN, SMALL, RMACH
   87: *     ..
   88: *     .. External Functions ..
   89:       LOGICAL            LSAME
   90:       EXTERNAL           LSAME
   91: *     ..
   92: *     .. Intrinsic Functions ..
   93:       INTRINSIC          DIGITS, EPSILON, HUGE, MAXEXPONENT,
   94:      $                   MINEXPONENT, RADIX, TINY
   95: *     ..
   96: *     .. Executable Statements ..
   97: *
   98: *
   99: *     Assume rounding, not chopping. Always.
  100: *
  101:       RND = ONE
  102: *
  103:       IF( ONE.EQ.RND ) THEN
  104:          EPS = EPSILON(ZERO) * 0.5
  105:       ELSE
  106:          EPS = EPSILON(ZERO)
  107:       END IF
  108: *
  109:       IF( LSAME( CMACH, 'E' ) ) THEN
  110:          RMACH = EPS
  111:       ELSE IF( LSAME( CMACH, 'S' ) ) THEN
  112:          SFMIN = TINY(ZERO)
  113:          SMALL = ONE / HUGE(ZERO)
  114:          IF( SMALL.GE.SFMIN ) THEN
  115: *
  116: *           Use SMALL plus a bit, to avoid the possibility of rounding
  117: *           causing overflow when computing  1/sfmin.
  118: *
  119:             SFMIN = SMALL*( ONE+EPS )
  120:          END IF
  121:          RMACH = SFMIN
  122:       ELSE IF( LSAME( CMACH, 'B' ) ) THEN
  123:          RMACH = RADIX(ZERO)
  124:       ELSE IF( LSAME( CMACH, 'P' ) ) THEN
  125:          RMACH = EPS * RADIX(ZERO)
  126:       ELSE IF( LSAME( CMACH, 'N' ) ) THEN
  127:          RMACH = DIGITS(ZERO)
  128:       ELSE IF( LSAME( CMACH, 'R' ) ) THEN
  129:          RMACH = RND
  130:       ELSE IF( LSAME( CMACH, 'M' ) ) THEN
  131:          RMACH = MINEXPONENT(ZERO)
  132:       ELSE IF( LSAME( CMACH, 'U' ) ) THEN
  133:          RMACH = tiny(zero)
  134:       ELSE IF( LSAME( CMACH, 'L' ) ) THEN
  135:          RMACH = MAXEXPONENT(ZERO)
  136:       ELSE IF( LSAME( CMACH, 'O' ) ) THEN
  137:          RMACH = HUGE(ZERO)
  138:       ELSE
  139:          RMACH = ZERO
  140:       END IF
  141: *
  142:       DLAMCH = RMACH
  143:       RETURN
  144: *
  145: *     End of DLAMCH
  146: *
  147:       END
  148: ************************************************************************
  149: *> \brief \b DLAMC3
  150: *> \details
  151: *> \b Purpose:
  152: *> \verbatim
  153: *> DLAMC3  is intended to force  A  and  B  to be stored prior to doing
  154: *> the addition of  A  and  B ,  for use in situations where optimizers
  155: *> might hold one of these in a register.
  156: *> \endverbatim
  157: *> \author LAPACK is a software package provided by Univ. of Tennessee, Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..
  158: *> \date November 2011
  159: *> \ingroup auxOTHERauxiliary
  160: *>
  161: *> \param[in] A
  162: *> \verbatim
  163: *>          A is a DOUBLE PRECISION
  164: *> \endverbatim
  165: *>
  166: *> \param[in] B
  167: *> \verbatim
  168: *>          B is a DOUBLE PRECISION
  169: *>          The values A and B.
  170: *> \endverbatim
  171: *>
  172:       DOUBLE PRECISION FUNCTION DLAMC3( A, B )
  173: *
  174: *  -- LAPACK auxiliary routine (version 3.4.0) --
  175: *     Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd..
  176: *     November 2010
  177: *
  178: *     .. Scalar Arguments ..
  179:       DOUBLE PRECISION   A, B
  180: *     ..
  181: * =====================================================================
  182: *
  183: *     .. Executable Statements ..
  184: *
  185:       DLAMC3 = A + B
  186: *
  187:       RETURN
  188: *
  189: *     End of DLAMC3
  190: *
  191:       END
  192: *
  193: ************************************************************************