Developer Reference

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

p?syevr

Computes selected eigenvalues and, optionally, eigenvectors of a real symmetric matrix using Relatively Robust Representation.

Syntax

call pssyevr
(
jobz
,
range
,
uplo
,
n
,
a
,
ia
,
ja
,
desca
,
vl
,
vu
,
il
,
iu
,
m
,
nz
,
w
,
z
,
iz
,
jz
,
descz
,
work
,
lwork
,
iwork
,
liwork
,
info
)
call pdsyevr
(
jobz
,
range
,
uplo
,
n
,
a
,
ia
,
ja
,
desca
,
vl
,
vu
,
il
,
iu
,
m
,
nz
,
w
,
z
,
iz
,
jz
,
descz
,
work
,
lwork
,
iwork
,
liwork
,
info
)
Include Files
Description
p?syevr
computes selected eigenvalues and, optionally, eigenvectors of a real symmetric matrix
A
distributed in 2D blockcyclic format by calling the recommended sequence of ScaLAPACK
routines
.
First, the matrix
A
is reduced to real symmetric tridiagonal form. Then, the eigenproblem is solved using the parallel MRRR algorithm. Last, if eigenvectors have been computed, a backtransformation is done.
Upon successful completion, each processor stores a copy of all computed eigenvalues in
w
. The eigenvector matrix
z
is stored in 2D block-cyclic format distributed over all processors.
Note that subsets of eigenvalues/vectors can be selected by specifying a range of values or a range of indices for the desired 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
jobz
(global)
CHARACTER
*1
Specifies whether or not to compute the eigenvectors:
= 'N': Compute eigenvalues only.
= 'V': Compute eigenvalues and eigenvectors.
range
(global)
CHARACTER
*1
= 'A': all eigenvalues will be found.
= 'V': all eigenvalues in the interval [
vl
,
vu
] will be found.
= 'I': the
il
-th through
iu
-th eigenvalues will be found.
uplo
(global)
CHARACTER
*1
Specifies whether the upper or lower triangular part of the symmetric matrix
A
is stored:
= 'U': Upper triangular
= 'L': Lower triangular
n
(global )
INTEGER
The number of rows and columns of the matrix
a
.
n
0
a
REAL
for
pssyevr
DOUBLE PRECISION
for
pdsyevr
Block cyclic array of global size
(
n
,
n
)
, local size
(
lld_a
,
LOC
c
(