HP MLIB User's Guide Vol. 1 7th Ed.

Chapter 2 Basic Vector Operations 173
Environmental inquiry F_SFPINFO/F_DFPINFO
Table 2-1 describes floating point parameters and values returned by FPINFO.
Table 2-1 FPINFO return values
Floating
point
parameter
Fortran77 named
constant
Description
Value in
IEEE single
Value in IEEE
double
BASE BLAS_BASE Base of machine 2 2
T BLAS_T Number of digits 24 53
RND BLAS_RND
Equals 1 when proper rounding
occurs in addition. Otherwise,
equals 0
11
IEEE BLAS_IEEE
Equals 1 when rounding in
addition is IEEE style.
Otherwise, equals 0
11
EMIN BLAS_EMIN
Minimum exponent before
(gradual) underflow
-126 -1022
EMAX BLAS_EMAX
Minimum exponent before
overflow
127 1023
EPS BLAS_EPS
Machine epsilon
PREC BLAS_PREC EPS*BASE
2
-23
2
-52
UN BLAS_UNDERFLOW
Underflow threshold
OV BLAS_OVERFLOW
Overflow threshold
SFMIN BLAS_SFMIN
Safe minimum, such that
does not overflow.
If < UN, SFMIN = UN.
Otherwise,
SFMIN = (1+EPS) / OV
EPS 0.5BASE
1 T–
if RND = 1=
EPS BASE
1 T–
if RND = 0=
2
24–
5e 8–≈ 2
53–
1e 16–≈
BASE
EMIN
=
2
126–
1e 38–≈ 2
1022–
1e 308–≈
BASE
EMAX 1+
1 EPS–()×=
2
128
1e38≈ 2
1024
1e308≈
1 SFMIN⁄
1OV⁄
2
126–
1e 38–≈ 2
1022–
1e 308–≈