Developer Reference

  • 2021.1
  • 12/04/2020
  • Public Content
Contents

p?labad

Returns the square root of the underflow and overflow thresholds if the exponent-range is very large.

Syntax

void
pslabad
(
MKL_INT
*ictxt
,
float
*small
,
float
*large
);
void
pdlabad
(
MKL_INT
*ictxt
,
double
*small
,
double
*large
);
Include Files
  • mkl_scalapack.h
Description
The
p?labad
function
takes as input the values computed by
p?lamch
for underflow and overflow, and returns the square root of each of these values if the log of
large
is sufficiently large. This
function
is intended to identify machines with a large exponent range, such as the Crays, and redefine the underflow and overflow limits to be the square roots of the values computed by
p?lamch
. This
function
is needed because
p?lamch
does not compensate for poor arithmetic in the upper half of the exponent range, as is found on a Cray.
In addition, this
function
performs a global minimization and maximization on these values, to support heterogeneous computing networks.
Input Parameters
ictxt
(global)
The BLACS context handle in which the computation takes place.
small
(local).
On entry, the underflow threshold as computed by
p?lamch
.
large
(local).
On entry, the overflow threshold as computed by
p?lamch
.
Output Parameters
small
(local).
On exit, if
log10
(
large
) is sufficiently large, the square root of
small
, otherwise unchanged.
large
(local).
On exit, if
log10
(
large
) is sufficiently large, the square root of
large
, otherwise unchanged.

Product and Performance Information

1

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