Annotation of rpl/lapack/lapack/dlamch.f, revision 1.11
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: *
59: *> \date November 2011
60: *
61: *> \ingroup auxOTHERauxiliary
62: *
63: * =====================================================================
1.1 bertrand 64: DOUBLE PRECISION FUNCTION DLAMCH( CMACH )
65: *
1.10 bertrand 66: * -- LAPACK auxiliary routine (version 3.4.0) --
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..--
1.10 bertrand 69: * November 2011
1.1 bertrand 70: *
71: * .. Scalar Arguments ..
72: CHARACTER CMACH
73: * ..
74: *
1.10 bertrand 75: * .. Scalar Arguments ..
76: DOUBLE PRECISION A, B
77: * ..
1.1 bertrand 78: *
79: * =====================================================================
80: *
81: * .. Parameters ..
82: DOUBLE PRECISION ONE, ZERO
83: PARAMETER ( ONE = 1.0D+0, ZERO = 0.0D+0 )
84: * ..
85: * .. Local Scalars ..
1.7 bertrand 86: DOUBLE PRECISION RND, EPS, SFMIN, SMALL, RMACH
1.1 bertrand 87: * ..
88: * .. External Functions ..
89: LOGICAL LSAME
90: EXTERNAL LSAME
91: * ..
1.7 bertrand 92: * .. Intrinsic Functions ..
93: INTRINSIC DIGITS, EPSILON, HUGE, MAXEXPONENT,
94: $ MINEXPONENT, RADIX, TINY
1.1 bertrand 95: * ..
96: * .. Executable Statements ..
97: *
1.7 bertrand 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)
1.1 bertrand 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
1.7 bertrand 123: RMACH = RADIX(ZERO)
1.1 bertrand 124: ELSE IF( LSAME( CMACH, 'P' ) ) THEN
1.7 bertrand 125: RMACH = EPS * RADIX(ZERO)
1.1 bertrand 126: ELSE IF( LSAME( CMACH, 'N' ) ) THEN
1.7 bertrand 127: RMACH = DIGITS(ZERO)
1.1 bertrand 128: ELSE IF( LSAME( CMACH, 'R' ) ) THEN
129: RMACH = RND
130: ELSE IF( LSAME( CMACH, 'M' ) ) THEN
1.7 bertrand 131: RMACH = MINEXPONENT(ZERO)
1.1 bertrand 132: ELSE IF( LSAME( CMACH, 'U' ) ) THEN
1.7 bertrand 133: RMACH = tiny(zero)
1.1 bertrand 134: ELSE IF( LSAME( CMACH, 'L' ) ) THEN
1.7 bertrand 135: RMACH = MAXEXPONENT(ZERO)
1.1 bertrand 136: ELSE IF( LSAME( CMACH, 'O' ) ) THEN
1.7 bertrand 137: RMACH = HUGE(ZERO)
138: ELSE
139: RMACH = ZERO
1.1 bertrand 140: END IF
141: *
142: DLAMCH = RMACH
143: RETURN
144: *
145: * End of DLAMCH
146: *
147: END
148: ************************************************************************
1.10 bertrand 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: *>
1.1 bertrand 172: DOUBLE PRECISION FUNCTION DLAMC3( A, B )
173: *
1.10 bertrand 174: * -- LAPACK auxiliary routine (version 3.4.0) --
1.1 bertrand 175: * Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd..
1.7 bertrand 176: * November 2010
1.1 bertrand 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: ************************************************************************
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