Annotation of rpl/lapack/lapack/dlamch.f, revision 1.17
1.10 bertrand 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: *
1.17 ! bertrand 59: *> \date November 2015
1.10 bertrand 60: *
61: *> \ingroup auxOTHERauxiliary
62: *
63: * =====================================================================
1.1 bertrand 64: DOUBLE PRECISION FUNCTION DLAMCH( CMACH )
65: *
1.17 ! bertrand 66: * -- LAPACK auxiliary routine (version 3.6.0) --
1.7 bertrand 67: * -- LAPACK is a software package provided by Univ. of Tennessee, --
68: * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
1.17 ! bertrand 69: * November 2015
1.1 bertrand 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 ..
1.7 bertrand 82: DOUBLE PRECISION RND, EPS, SFMIN, SMALL, RMACH
1.1 bertrand 83: * ..
84: * .. External Functions ..
85: LOGICAL LSAME
86: EXTERNAL LSAME
87: * ..
1.7 bertrand 88: * .. Intrinsic Functions ..
89: INTRINSIC DIGITS, EPSILON, HUGE, MAXEXPONENT,
90: $ MINEXPONENT, RADIX, TINY
1.1 bertrand 91: * ..
92: * .. Executable Statements ..
93: *
1.7 bertrand 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)
1.1 bertrand 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
1.7 bertrand 119: RMACH = RADIX(ZERO)
1.1 bertrand 120: ELSE IF( LSAME( CMACH, 'P' ) ) THEN
1.7 bertrand 121: RMACH = EPS * RADIX(ZERO)
1.1 bertrand 122: ELSE IF( LSAME( CMACH, 'N' ) ) THEN
1.7 bertrand 123: RMACH = DIGITS(ZERO)
1.1 bertrand 124: ELSE IF( LSAME( CMACH, 'R' ) ) THEN
125: RMACH = RND
126: ELSE IF( LSAME( CMACH, 'M' ) ) THEN
1.7 bertrand 127: RMACH = MINEXPONENT(ZERO)
1.1 bertrand 128: ELSE IF( LSAME( CMACH, 'U' ) ) THEN
1.7 bertrand 129: RMACH = tiny(zero)
1.1 bertrand 130: ELSE IF( LSAME( CMACH, 'L' ) ) THEN
1.7 bertrand 131: RMACH = MAXEXPONENT(ZERO)
1.1 bertrand 132: ELSE IF( LSAME( CMACH, 'O' ) ) THEN
1.7 bertrand 133: RMACH = HUGE(ZERO)
134: ELSE
135: RMACH = ZERO
1.1 bertrand 136: END IF
137: *
138: DLAMCH = RMACH
139: RETURN
140: *
141: * End of DLAMCH
142: *
143: END
144: ************************************************************************
1.10 bertrand 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..
1.17 ! bertrand 154: *> \date November 2015
1.10 bertrand 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: *>
1.1 bertrand 168: DOUBLE PRECISION FUNCTION DLAMC3( A, B )
169: *
1.17 ! bertrand 170: * -- LAPACK auxiliary routine (version 3.6.0) --
1.1 bertrand 171: * Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd..
1.7 bertrand 172: * November 2010
1.1 bertrand 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: ************************************************************************
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