Developer Reference

  • 2020.2
  • 07/15/2020
  • Public Content
Contents

p?stebz

Computes the eigenvalues of a symmetric tridiagonal matrix by bisection.

Syntax

call psstebz
(
ictxt
,
range
,
order
,
n
,
vl
,
vu
,
il
,
iu
,
abstol
,
d
,
e
,
m
,
nsplit
,
w
,
iblock
,
isplit
,
work
,
iwork
,
liwork
,
info
)
call pdstebz
(
ictxt
,
range
,
order
,
n
,
vl
,
vu
,
il
,
iu
,
abstol
,
d
,
e
,
m
,
nsplit
,
w
,
iblock
,
isplit
,
work
,
iwork
,
liwork
,
info
)
Include Files
Description
The
p?stebz
routine
computes the eigenvalues of a symmetric tridiagonal matrix in parallel. These may be all eigenvalues, all eigenvalues in the interval
[
vl
vu
]
, or the eigenvalues
indexed
il
through
iu
. A static partitioning of work is done at the beginning of
p?stebz
which results in all processes finding an (almost) equal number of eigenvalues.
Optimization Notice
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 reserved 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
This notice covers the following instruction sets: SSE2, SSE4.2, AVX2, AVX-512.
Input Parameters
ictxt
(global)
INTEGER
.
The
BLACS
context handle.
range
(global)
CHARACTER
.
Must be
'A'
or
'V'
or
'I'
.
If
range
=
'A'
, the
routine
computes all eigenvalues.
If
range
=
'V'
, the
routine
computes eigenvalues in the interval
[
vl
,
vu
]
.
If
range
=
'I'
, the
routine
computes eigenvalues
with indices
il
through
iu
.
order
(global)
CHARACTER
.
Must be
'B'
or
'E'
.
If
order
=
'B'
, the eigenvalues are to be ordered from smallest to largest within each split-off block.
If
order
=
'E'
, the eigenvalues for the entire matrix are to be ordered from smallest to largest.
n
(global)
INTEGER
.
The order of the tridiagonal matrix
T
(
n
0)
.
vl
,
vu
(global)
REAL
for
psstebz
DOUBLE PRECISION
for
pdstebz
.
If
range
=
'V'
, the
routine
computes the lower and the upper bounds for the eigenvalues on the interval
[
1
,
vu
]
.
If
range
=
'A'
or
'I'
,
vl
and
vu
are not referenced.
il
,
iu
(global)
INTEGER
.
Constraint:
1≤
il
iu
n
.
If
range
=
'I'
, the index of the