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 * ===================================================================== 76 * 77 * .. Parameters .. 78 DOUBLE PRECISION ONE, ZERO 79 PARAMETER ( ONE = 1.0D+0, ZERO = 0.0D+0 ) 80 * .. 81 * .. Local Scalars .. 82 DOUBLE PRECISION RND, EPS, SFMIN, SMALL, RMACH 83 * .. 84 * .. External Functions .. 85 LOGICAL LSAME 86 EXTERNAL LSAME 87 * .. 88 * .. Intrinsic Functions .. 89 INTRINSIC DIGITS, EPSILON, HUGE, MAXEXPONENT, 90 $ MINEXPONENT, RADIX, TINY 91 * .. 92 * .. Executable Statements .. 93 * 94 * 95 * Assume rounding, not chopping. Always. 96 * 97 RND = ONE 98 * 99 IF( ONE.EQ.RND ) THEN 100 EPS = EPSILON(ZERO) * 0.5 101 ELSE 102 EPS = EPSILON(ZERO) 103 END IF 104 * 105 IF( LSAME( CMACH, 'E' ) ) THEN 106 RMACH = EPS 107 ELSE IF( LSAME( CMACH, 'S' ) ) THEN 108 SFMIN = TINY(ZERO) 109 SMALL = ONE / HUGE(ZERO) 110 IF( SMALL.GE.SFMIN ) THEN 111 * 112 * Use SMALL plus a bit, to avoid the possibility of rounding 113 * causing overflow when computing 1/sfmin. 114 * 115 SFMIN = SMALL*( ONE+EPS ) 116 END IF 117 RMACH = SFMIN 118 ELSE IF( LSAME( CMACH, 'B' ) ) THEN 119 RMACH = RADIX(ZERO) 120 ELSE IF( LSAME( CMACH, 'P' ) ) THEN 121 RMACH = EPS * RADIX(ZERO) 122 ELSE IF( LSAME( CMACH, 'N' ) ) THEN 123 RMACH = DIGITS(ZERO) 124 ELSE IF( LSAME( CMACH, 'R' ) ) THEN 125 RMACH = RND 126 ELSE IF( LSAME( CMACH, 'M' ) ) THEN 127 RMACH = MINEXPONENT(ZERO) 128 ELSE IF( LSAME( CMACH, 'U' ) ) THEN 129 RMACH = tiny(zero) 130 ELSE IF( LSAME( CMACH, 'L' ) ) THEN 131 RMACH = MAXEXPONENT(ZERO) 132 ELSE IF( LSAME( CMACH, 'O' ) ) THEN 133 RMACH = HUGE(ZERO) 134 ELSE 135 RMACH = ZERO 136 END IF 137 * 138 DLAMCH = RMACH 139 RETURN 140 * 141 * End of DLAMCH 142 * 143 END 144 ************************************************************************ 145 *> \brief \b DLAMC3 146 *> \details 147 *> \b Purpose: 148 *> \verbatim 149 *> DLAMC3 is intended to force A and B to be stored prior to doing 150 *> the addition of A and B , for use in situations where optimizers 151 *> might hold one of these in a register. 152 *> \endverbatim 153 *> \author LAPACK is a software package provided by Univ. of Tennessee, Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd.. 154 *> \date November 2011 155 *> \ingroup auxOTHERauxiliary 156 *> 157 *> \param[in] A 158 *> \verbatim 159 *> A is a DOUBLE PRECISION 160 *> \endverbatim 161 *> 162 *> \param[in] B 163 *> \verbatim 164 *> B is a DOUBLE PRECISION 165 *> The values A and B. 166 *> \endverbatim 167 *> 168 DOUBLE PRECISION FUNCTION DLAMC3( A, B ) 169 * 170 * -- LAPACK auxiliary routine (version 3.4.0) -- 171 * Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. 172 * November 2010 173 * 174 * .. Scalar Arguments .. 175 DOUBLE PRECISION A, B 176 * .. 177 * ===================================================================== 178 * 179 * .. Executable Statements .. 180 * 181 DLAMC3 = A + B 182 * 183 RETURN 184 * 185 * End of DLAMC3 186 * 187 END 188 * 189 ************************************************************************ 190
