Developer Reference

Contents

?lamch

Determines machine parameters for floating-point arithmetic.

Syntax

float
LAPACKE_slamch
(
char
cmach
);
double
LAPACKE_dlamch
(
char
cmach
);
Include Files
  • mkl.h
Description
The function
?lamch
determines single precision and double precision machine parameters.
Input Parameters
cmach
Specifies the value to be returned by
?lamch
:
= '
E
' or '
e
',
val
=
eps
= '
S
' or '
s
',
val
=
sfmin
= '
B
' or '
b
',
val
=
base
= '
P
' or '
p
',
val
=
eps
*
base
= '
n
' or '
n
',
val
=
t
= '
R
' or '
r
',
val
=
rnd
= '
M
' or '
m
',
val
=
emin
= '
U
' or '
u
',
val
=
rmin
=
'L'
or '
l
',
val
=
emax
= '
O
' or '
o
',
val
=
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
).
You can use a character string for
cmach
instead of a single character in order to make your code more readable. The first character of the string determines the value to be returned. For example, '
Precision
' is interpreted as '
p
'.
Output Parameters
val
Value returned by the function.

Product and Performance Information

1

Performance varies by use, configuration and other factors. Learn more at www.Intel.com/PerformanceIndex.