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NAME

       PCLASE2  -  initialize  an  M-by-N distributed matrix sub( A ) denoting
       A(IA:IA+M-1,JA:JA+N-1) to  BETA  on  the  diagonal  and  ALPHA  on  the
       offdiagonals

SYNOPSIS

       SUBROUTINE PCLASE2( UPLO, M, N, ALPHA, BETA, A, IA, JA, DESCA )

           CHARACTER       UPLO

           INTEGER         IA, JA, M, N

           COMPLEX         ALPHA, BETA

           INTEGER         DESCA( * )

           COMPLEX         A( * )

PURPOSE

       PCLASE2  initializes  an  M-by-N  distributed  matrix sub( A ) denoting
       A(IA:IA+M-1,JA:JA+N-1) to  BETA  on  the  diagonal  and  ALPHA  on  the
       offdiagonals.   PCLASE2  requires  that  only  dimension  of the matrix
       operand is distributed.

       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

       UPLO    (global input) CHARACTER
               Specifies  the  part  of  the distributed matrix sub( A ) to be
               set:
               = ’U’:      Upper triangular part is set;  the  strictly  lower
               triangular  part  of sub( A ) is not changed; = ’L’:      Lower
               triangular part is set; the strictly upper triangular  part  of
               sub( A ) is not changed; Otherwise:  All of the matrix sub( A )
               is set.

       M       (global input) INTEGER
               The number of rows to be operated on i.e the number of rows  of
               the distributed submatrix sub( A ). M >= 0.

       N       (global input) INTEGER
               The  number  of  columns  to  be  operated on i.e the number of
               columns of the distributed submatrix sub( A ). N >= 0.

       ALPHA   (global input) COMPLEX
               The constant to which the offdiagonal elements are to be set.

       BETA    (global input) COMPLEX
               The constant to which the diagonal elements are to be set.

       A       (local output) COMPLEX pointer into the local memory
               to an array  of  dimension  (LLD_A,LOCc(JA+N-1)).   This  array
               contains the local pieces of the distributed matrix sub( A ) to
               be set.  On exit, the leading M-by-N submatrix sub( A ) is  set
               as follows:

               if UPLO = ’U’, A(IA+i-1,JA+j-1) = ALPHA, 1<=i<=j-1, 1<=j<=N, if
               UPLO =  ’L’,  A(IA+i-1,JA+j-1)  =  ALPHA,  j+1<=i<=M,  1<=j<=N,
               otherwise,      A(IA+i-1,JA+j-1)  =  ALPHA,  1<=i<=M,  1<=j<=N,
               IA+i.NE.JA+j, and,  for  all  UPLO,  A(IA+i-1,JA+i-1)  =  BETA,
               1<=i<=min(M,N).

       IA      (global input) INTEGER
               The row index in the global array A indicating the first row of
               sub( A ).

       JA      (global input) INTEGER
               The column index in the global array  A  indicating  the  first
               column of sub( A ).

       DESCA   (global and local input) INTEGER array of dimension DLEN_.
               The array descriptor for the distributed matrix A.