Man Linux: Main Page and Category List

NAME

       PSLASCL  -  multiplie  the  M-by-N  real  distributed  matrix  sub( A )
       denoting A(IA:IA+M-1,JA:JA+N-1) by the real scalar CTO/CFROM

SYNOPSIS

       SUBROUTINE PSLASCL( TYPE, CFROM, CTO, M, N, A, IA, JA, DESCA, INFO )

           CHARACTER       TYPE

           INTEGER         IA, INFO, JA, M, N

           REAL            CFROM, CTO

           INTEGER         DESCA( * )

           REAL            A( * )

PURPOSE

       PSLASCL multiplies the M-by-N real distributed matrix sub( A ) denoting
       A(IA:IA+M-1,JA:JA+N-1)  by  the  real  scalar  CTO/CFROM.  This is done
       without over/underflow as long as the final result CTO * A(I,J) / CFROM
       does  not  over/underflow.  TYPE  specifies  that sub( A ) may be full,
       upper triangular, lower triangular or upper Hessenberg.

       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

       TYPE    (global input) CHARACTER
               TYPE  indices the storage type of the input distributed matrix.
               = ’G’:  sub( A ) is a full matrix,
               = ’L’:  sub( A ) is a lower triangular matrix,
               = ’U’:  sub( A ) is an upper triangular matrix,
               = ’H’:  sub( A ) is an upper Hessenberg matrix.

       CFROM   (global input) REAL
               CTO     (global input) REAL The distributed matrix sub( A )  is
               multiplied   by   CTO/CFROM.    A(I,J)   is   computed  without
               over/underflow if the final result CTO * A(I,J) / CFROM can  be
               represented without over/underflow.  CFROM must be nonzero.

       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.

       A       (local input/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 ). On exit, this array contains the local pieces of the
               distributed matrix multiplied by CTO/CFROM.

       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.

       INFO    (local output) INTEGER
               = 0:  successful exit
               < 0:  If the i-th argument is an array and the j-entry  had  an
               illegal  value, then INFO = -(i*100+j), if the i-th argument is
               a scalar and had an illegal value, then INFO = -i.