PDLAEVSWP - 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
- SUBROUTINE PDLAEVSWP(
- N, ZIN, LDZI, Z, IZ, JZ, DESCZ, NVS, KEY, WORK, LWORK )
INTEGER IZ, JZ, LDZI, LWORK, N INTEGER DESCZ( * ), KEY( * ), NVS( * ) DOUBLE
PRECISION WORK( * ), Z( * ), ZIN( LDZI, * )
PDLAEVSWP 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
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) DOUBLE PRECISION 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) DOUBLE PRECISION 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) DOUBLE PRECISION array, dimension (LWORK)
- LWORK (local input) INTEGER dimension of WORK