Developer Reference

  • 0.10
  • 10/21/2020
  • Public Content
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

Intel's compilers may or may not optimize to the same degree for non-Intel microprocessors for optimizations that are not unique to Intel microprocessors. These optimizations include SSE2, SSE3, and SSSE3 instruction sets and other optimizations. Intel does not guarantee the availability, functionality, or effectiveness of any optimization on microprocessors not manufactured by Intel. Microprocessor-dependent optimizations in this product are intended for use with Intel microprocessors. Certain optimizations not specific to Intel microarchitecture are reserverd for Intel microprocessors. Please refer to the applicable product User and Reference Guides for more information regarding the specific instruction sets covered by this notice.

Notice revision #20110804