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    1: *> \brief \b SLAMCH
    2: *
    3: *  =========== DOCUMENTATION ===========
    4: *
    5: * Online html documentation available at 
    6: *            http://www.netlib.org/lapack/explore-html/ 
    7: *
    8: *  Definition:
    9: *  ===========
   10: *
   11: *      REAL             FUNCTION SLAMCH( CMACH )
   12: *
   13: *     .. Scalar Arguments ..
   14: *      CHARACTER          CMACH
   15: *     ..
   16: *  
   17: *
   18: *> \par Purpose:
   19: *  =============
   20: *>
   21: *> \verbatim
   22: *>
   23: *> SLAMCH determines single precision machine parameters.
   24: *> \endverbatim
   25: *
   26: *  Arguments:
   27: *  ==========
   28: *
   29: *> \param[in] CMACH
   30: *> \verbatim
   31: *>          Specifies the value to be returned by SLAMCH:
   32: *>          = 'E' or 'e',   SLAMCH := eps
   33: *>          = 'S' or 's ,   SLAMCH := sfmin
   34: *>          = 'B' or 'b',   SLAMCH := base
   35: *>          = 'P' or 'p',   SLAMCH := eps*base
   36: *>          = 'N' or 'n',   SLAMCH := t
   37: *>          = 'R' or 'r',   SLAMCH := rnd
   38: *>          = 'M' or 'm',   SLAMCH := emin
   39: *>          = 'U' or 'u',   SLAMCH := rmin
   40: *>          = 'L' or 'l',   SLAMCH := emax
   41: *>          = 'O' or 'o',   SLAMCH := rmax
   42: *>          where
   43: *>          eps   = relative machine precision
   44: *>          sfmin = safe minimum, such that 1/sfmin does not overflow
   45: *>          base  = base of the machine
   46: *>          prec  = eps*base
   47: *>          t     = number of (base) digits in the mantissa
   48: *>          rnd   = 1.0 when rounding occurs in addition, 0.0 otherwise
   49: *>          emin  = minimum exponent before (gradual) underflow
   50: *>          rmin  = underflow threshold - base**(emin-1)
   51: *>          emax  = largest exponent before overflow
   52: *>          rmax  = overflow threshold  - (base**emax)*(1-eps)
   53: *> \endverbatim
   54: *
   55: *  Authors:
   56: *  ========
   57: *
   58: *> \author Univ. of Tennessee 
   59: *> \author Univ. of California Berkeley 
   60: *> \author Univ. of Colorado Denver 
   61: *> \author NAG Ltd. 
   62: *
   63: *> \date November 2011
   64: *
   65: *> \ingroup auxOTHERauxiliary
   66: *
   67: *  =====================================================================
   68:       REAL             FUNCTION SLAMCH( CMACH )
   69: *
   70: *  -- LAPACK auxiliary routine (version 3.4.0) --
   71: *  -- LAPACK is a software package provided by Univ. of Tennessee,    --
   72: *  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
   73: *     November 2011
   74: *
   75: *     .. Scalar Arguments ..
   76:       CHARACTER          CMACH
   77: *     ..
   78: *
   79: * =====================================================================
   80: *
   81: *     .. Parameters ..
   82:       REAL               ONE, ZERO
   83:       PARAMETER          ( ONE = 1.0E+0, ZERO = 0.0E+0 )
   84: *     ..
   85: *     .. Local Scalars ..
   86:       REAL               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:       SLAMCH = RMACH
  143:       RETURN
  144: *
  145: *     End of SLAMCH
  146: *
  147:       END
  148: ************************************************************************
  149: *> \brief \b SLAMC3
  150: *> \details
  151: *> \b Purpose:
  152: *> \verbatim
  153: *> SLAMC3  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: *> \endverbatim
  164: *>
  165: *> \param[in] B
  166: *> \verbatim
  167: *>          The values A and B.
  168: *> \endverbatim
  169: *>
  170: *
  171:       REAL             FUNCTION SLAMC3( A, B )
  172: *
  173: *  -- LAPACK auxiliary routine (version 3.4.0) --
  174: *     Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd..
  175: *     November 2010
  176: *
  177: *     .. Scalar Arguments ..
  178:       REAL               A, B
  179: *     ..
  180: * =====================================================================
  181: *
  182: *     .. Executable Statements ..
  183: *
  184:       SLAMC3 = A + B
  185: *
  186:       RETURN
  187: *
  188: *     End of SLAMC3
  189: *
  190:       END
  191: *
  192: ************************************************************************