NAME

       PSLASET - 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 PSLASET( UPLO, M, N, ALPHA, BETA, A, IA, JA, DESCA )

           CHARACTER       UPLO

           INTEGER         IA, JA, M, N

           REAL            ALPHA, BETA

           INTEGER         DESCA( * )

           REAL            A( * )

PURPOSE

       PSLASET 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.

       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) REAL
               The constant to which the offdiagonal elements are to be set.

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

       A       (local output) REAL 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.