pslaevswp(3)
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 distributed over. The context itself is global, 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