PCLAEVSWP(3)  ScaLAPACK routine of NEC Numeric Library Collection PCLAEVSWP(3)



NAME
       PCLAEVSWP  -  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 PCLAEVSWP( N,  ZIN, LDZI, Z, IZ, JZ, DESCZ, NVS, KEY, RWORK,
                             LRWORK )

           INTEGER           IZ, JZ, LDZI, LRWORK, N

           INTEGER           DESCZ( * ), KEY( * ), NVS( * )

           REAL              RWORK( * ), ZIN( LDZI, * )

           COMPLEX           Z( * )

PURPOSE
       PCLAEVSWP 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  vec-
       tor.  This vector stores the information required to establish the map-
       ping 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 col-
       umn.
       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) COMPLEX 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 sub-
               matrix 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.

       RWORK    (local workspace) REAL array, dimension (LRWORK)

       LRWORK   (local input) INTEGER dimension of RWORK



ScaLAPACK routine               31 October 2017                   PCLAEVSWP(3)