NAME
PSLAEVSWP - move the eigenvectors (potentially unsorted) from where
they are computed, to a ScaLAPACK standard block cyclic array, sorted
so that the corresponding eigenvalues are sorted
SYNOPSIS
SUBROUTINE PSLAEVSWP( N, ZIN, LDZI, Z, IZ, JZ, DESCZ, NVS, KEY, WORK,
LWORK )
INTEGER IZ, JZ, LDZI, LWORK, N
INTEGER DESCZ( * ), KEY( * ), NVS( * )
REAL WORK( * ), Z( * ), ZIN( LDZI, * )
PURPOSE
PSLAEVSWP moves the eigenvectors (potentially unsorted) from where they
are computed, to a ScaLAPACK standard block cyclic array, sorted so
that the corresponding eigenvalues are sorted.
Notes
=====
Each global data object is described by an associated description
vector. This vector stores the information required to establish the
mapping between an object element and its corresponding process and
memory location.
Let A be a generic term for any 2D block cyclicly distributed array.
Such a global array has an associated description vector DESCA. In the
following comments, the character _ should be read as "of the global
array".
NOTATION STORED IN EXPLANATION
--------------- -------------- --------------------------------------
DTYPE_A(global) DESCA( DTYPE_ )The descriptor type. In this case,
DTYPE_A = 1.
CTXT_A (global) DESCA( CTXT_ ) The BLACS context handle, indicating
the BLACS process grid A is distribu-
ted over. The context itself is glo-
bal, but the handle (the integer
value) may vary.
M_A (global) DESCA( M_ ) The number of rows in the global
array A.
N_A (global) DESCA( N_ ) The number of columns in the global
array A.
MB_A (global) DESCA( MB_ ) The blocking factor used to distribute
the rows of the array.
NB_A (global) DESCA( NB_ ) The blocking factor used to distribute
the columns of the array.
RSRC_A (global) DESCA( RSRC_ ) The process row over which the first
row of the array A is distributed.
CSRC_A (global) DESCA( CSRC_ ) The process column over which the
first column of the array A is
distributed.
LLD_A (local) DESCA( LLD_ ) The leading dimension of the local
array. LLD_A >= MAX(1,LOCr(M_A)).
Let K be the number of rows or columns of a distributed matrix, and
assume that its process grid has dimension p x q.
LOCr( K ) denotes the number of elements of K that a process would
receive if K were distributed over the p processes of its process
column.
Similarly, LOCc( K ) denotes the number of elements of K that a process
would receive if K were distributed over the q processes of its process
row.
The values of LOCr() and LOCc() may be determined via a call to the
ScaLAPACK tool function, NUMROC:
LOCr( M ) = NUMROC( M, MB_A, MYROW, RSRC_A, NPROW ),
LOCc( N ) = NUMROC( N, NB_A, MYCOL, CSRC_A, NPCOL ). An upper
bound for these quantities may be computed by:
LOCr( M ) <= ceil( ceil(M/MB_A)/NPROW )*MB_A
LOCc( N ) <= ceil( ceil(N/NB_A)/NPCOL )*NB_A
ARGUMENTS
NP = the number of rows local to a given process. NQ = the number of
columns local to a given process.
N (global input) INTEGER
The order of the matrix A. N >= 0.
ZIN (local input) REAL array,
dimension ( LDZI, NVS(iam) ) The eigenvectors on input. Each
eigenvector resides entirely in one process. Each process
holds a contiguous set of NVS(iam) eigenvectors. The first
eigenvector which the process holds is: sum for i=[0,iam-1) of
NVS(i)
LDZI (locl input) INTEGER
leading dimension of the ZIN array
Z (local output) REAL array
global dimension (N, N), local dimension (DESCZ(DLEN_), NQ) The
eigenvectors on output. The eigenvectors are distributed in a
block cyclic manner in both dimensions, with a block size of
NB.
IZ (global input) INTEGER
Z’s global row index, which points to the beginning of the
submatrix which is to be operated on.
JZ (global input) INTEGER
Z’s global column index, which points to the beginning of the
submatrix which is to be operated on.
DESCZ (global and local input) INTEGER array of dimension DLEN_.
The array descriptor for the distributed matrix Z.
NVS (global input) INTEGER array, dimension( nprocs+1 )
nvs(i) = number of processes number of eigenvectors held by
processes [0,i-1) nvs(1) = number of eigen vectors held by
[0,1-1) == 0 nvs(nprocs+1) = number of eigen vectors held by
[0,nprocs) == total number of eigenvectors
KEY (global input) INTEGER array, dimension( N )
Indicates the actual index (after sorting) for each of the
eigenvectors.
WORK (local workspace) REAL array, dimension (LWORK)
LWORK (local input) INTEGER dimension of WORK