determine floating-point parameters
pr = number_properties(prop)
string
real or boolean scalar
This function may be used to get the characteristic
numbers/properties of the floating point set denoted here by
F(b,p,emin,emax)
(usually the 64 bits float numbers set
prescribe by IEEE 754). Numbers of F
are of the
form:
sign * m * b^e
e
is the exponent and m
the
mantissa:
the digits are in
[0, b-1]
and e
in [emin, emax]
, the number is
said "normalized" if
. The following queries may be used:
then pr
is the radix b
of the set F
then pr
is the number of digits
p
then pr
is the max positive float of
F
then pr
is the min positive normalized
float of F
then pr
is a boolean (%t if denormalized
numbers are used)
then if denorm = %t, pr
is the min positive
denormalized number else pr
= tiny
then pr
is the epsilon machine ( generally
(
) which is the relative max error
between a real
x
(such than
|x|
in [tiny, huge]
) and
fl(x)
, its floating point approximation in
F
then pr
is emin
then pr
is emax
![]() | This function uses the lapack routine dlamch to get the machine
parameters (the names (radix, digit, huge, etc...) are those recommended by the LIA 1
standard and are different from the corresponding lapack's ones). |
![]() | Sometimes you can see the following definition for the epsilon machine :
![]() ![]() ![]() |