 LAPACK 3.11.0 LAPACK: Linear Algebra PACKage
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## ◆ slamch()

 real function slamch ( character CMACH )

SLAMCH

Purpose:
` SLAMCH determines single precision machine parameters.`
Parameters
 [in] CMACH ``` CMACH is CHARACTER*1 Specifies the value to be returned by SLAMCH: = 'E' or 'e', SLAMCH := eps = 'S' or 's , SLAMCH := sfmin = 'B' or 'b', SLAMCH := base = 'P' or 'p', SLAMCH := eps*base = 'N' or 'n', SLAMCH := t = 'R' or 'r', SLAMCH := rnd = 'M' or 'm', SLAMCH := emin = 'U' or 'u', SLAMCH := rmin = 'L' or 'l', SLAMCH := emax = 'O' or 'o', SLAMCH := rmax where eps = relative machine precision sfmin = safe minimum, such that 1/sfmin does not overflow base = base of the machine prec = eps*base t = number of (base) digits in the mantissa rnd = 1.0 when rounding occurs in addition, 0.0 otherwise emin = minimum exponent before (gradual) underflow rmin = underflow threshold - base**(emin-1) emax = largest exponent before overflow rmax = overflow threshold - (base**emax)*(1-eps)```

Definition at line 67 of file slamch.f.

68*
69* -- LAPACK auxiliary routine --
70* -- LAPACK is a software package provided by Univ. of Tennessee, --
71* -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
72*
73* .. Scalar Arguments ..
74 CHARACTER CMACH
75* ..
76*
77* =====================================================================
78*
79* .. Parameters ..
80 REAL ONE, ZERO
81 parameter( one = 1.0e+0, zero = 0.0e+0 )
82* ..
83* .. Local Scalars ..
84 REAL RND, EPS, SFMIN, SMALL, RMACH
85* ..
86* .. External Functions ..
87 LOGICAL LSAME
88 EXTERNAL lsame
89* ..
90* .. Intrinsic Functions ..
91 INTRINSIC digits, epsilon, huge, maxexponent,
93* ..
94* .. Executable Statements ..
95*
96*
97* Assume rounding, not chopping. Always.
98*
99 rnd = one
100*
101 IF( one.EQ.rnd ) THEN
102 eps = epsilon(zero) * 0.5
103 ELSE
104 eps = epsilon(zero)
105 END IF
106*
107 IF( lsame( cmach, 'E' ) ) THEN
108 rmach = eps
109 ELSE IF( lsame( cmach, 'S' ) ) THEN
110 sfmin = tiny(zero)
111 small = one / huge(zero)
112 IF( small.GE.sfmin ) THEN
113*
114* Use SMALL plus a bit, to avoid the possibility of rounding
115* causing overflow when computing 1/sfmin.
116*
117 sfmin = small*( one+eps )
118 END IF
119 rmach = sfmin
120 ELSE IF( lsame( cmach, 'B' ) ) THEN
122 ELSE IF( lsame( cmach, 'P' ) ) THEN
123 rmach = eps * radix(zero)
124 ELSE IF( lsame( cmach, 'N' ) ) THEN
125 rmach = digits(zero)
126 ELSE IF( lsame( cmach, 'R' ) ) THEN
127 rmach = rnd
128 ELSE IF( lsame( cmach, 'M' ) ) THEN
129 rmach = minexponent(zero)
130 ELSE IF( lsame( cmach, 'U' ) ) THEN
131 rmach = tiny(zero)
132 ELSE IF( lsame( cmach, 'L' ) ) THEN
133 rmach = maxexponent(zero)
134 ELSE IF( lsame( cmach, 'O' ) ) THEN
135 rmach = huge(zero)
136 ELSE
137 rmach = zero
138 END IF
139*
140 slamch = rmach
141 RETURN
142*
143* End of SLAMCH
144*
logical function lsame(CA, CB)
LSAME
Definition: lsame.f:53
real function slamch(CMACH)
SLAMCH
Definition: slamch.f:68
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