Developer Reference

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

p?laconsb

Looks for two consecutive small subdiagonal elements.

Syntax

void
pslaconsb
(
const
float
*
a
,
const
MKL_INT
*
desca
,
const
MKL_INT
*
i
,
const
MKL_INT
*
l
,
MKL_INT
*
m
,
const
float
*
h44
,
const
float
*
h33
,
const
float
*
h43h34
,
float
*
buf
,
const
MKL_INT
*
lwork
);
void
pdlaconsb
(
const
double
*
a
,
const
MKL_INT
*
desca
,
const
MKL_INT
*
i
,
const
MKL_INT
*
l
,
MKL_INT
*
m
,
const
double
*
h44
,
const
double
*
h33
,
const
double
*
h43h34
,
double
*
buf
,
const
MKL_INT
*
lwork
);
void
pclaconsb
(
const
MKL_Complex8
*
a
,
const
MKL_INT
*
desca
,
const
MKL_INT
*
i
,
const
MKL_INT
*
l
,
MKL_INT
*
m
,
const
MKL_Complex8
*
h44
,
const
MKL_Complex8
*
h33
,
const
MKL_Complex8
*
h43h34
,
MKL_Complex8
*
buf
,
const
MKL_INT
*
lwork
);
void
pzlaconsb
(
const
MKL_Complex16
*
a
,
const
MKL_INT
*
desca
,
const
MKL_INT
*
i
,
const
MKL_INT
*
l
,
MKL_INT
*
m
,
const
MKL_Complex16
*
h44
,
const
MKL_Complex16
*
h33
,
const
MKL_Complex16
*
h43h34
,
MKL_Complex16
*
buf
,
const
MKL_INT
*
lwork
);
Include Files
  • mkl_scalapack.h
Description
The
p?laconsb
function
looks for two consecutive small subdiagonal elements by analyzing the effect of starting a double shift
QR
iteration given by
h44
,
h33
, and
h43h34
to see if this process makes a subdiagonal negligible.
Input Parameters
a
(local)
Array of size
lld_a
*
LOCc
(
n_a
)
. On entry, the Hessenberg matrix whose tridiagonal part is being scanned. Unchanged on exit.
desca
(global and local)
Array of size
dlen_
. The array descriptor for the distributed matrix
A
.
i
(global)
The global location of the bottom of the unreduced submatrix of
A
. Unchanged on exit.
l
(global)
The global location of the top of the unreduced submatrix of
A
. Unchanged on exit.
h44
,
h33
,
h43h34
(global).
These three values are for the double shift
QR
iteration.
lwork
(local)
This must be at least
7*ceil(ceil( (
i
-l)/
mb_a
)/lcm(
nprow
,
npcol
))
. Here
lcm
is the least common multiple and
nprow
*
npcol
is the logical grid size.
Output Parameters
m
(global). On exit, this yields the starting location of the
QR
double shift. This will satisfy:
l
m
i
-2.
buf
(local).
Array of size
lwork
.

Product and Performance Information

1

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