source: pacpussensors/trunk/Vislab/lib3dv/eigen/lapack/slamch.f@ 137

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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************************************************************************
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