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Man Pages


Manual Reference Pages  -  PSLACP2 (l)

NAME

PSLACP2 - copie all or part of a distributed matrix A to another distributed matrix B

CONTENTS

Synopsis
Purpose
Arguments

SYNOPSIS

SUBROUTINE PSLACP2( UPLO, M, N, A, IA, JA, DESCA, B, IB, JB, DESCB )
    CHARACTER UPLO
    INTEGER IA, IB, JA, JB, M, N
    INTEGER DESCA( * ), DESCB( * )
    REAL A( * ), B( * )

PURPOSE

PSLACP2 copies all or part of a distributed matrix A to another distributed matrix B. No communication is performed, PSLACP2 performs a local copy sub( A ) := sub( B ), where sub( A ) denotes A(IA:IA+M-1,JA:JA+N-1) and sub( B ) denotes B(IB:IB+M-1,JB:JB+N-1). PSLACP2 requires that only dimension of the matrix operands 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 copied:
= ’U’: Upper triangular part is copied; the strictly lower triangular part of sub( A ) is not referenced; = ’L’: Lower triangular part is copied; the strictly upper triangular part of sub( A ) is not referenced; Otherwise: All of the matrix sub( A ) is copied.
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) 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 copied from.
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.
B (local output) REAL pointer into the local memory
  to an array of dimension (LLD_B, LOCc(JB+N-1) ). This array contains on exit the local pieces of the distributed matrix sub( B ) set as follows:

if UPLO = ’U’, B(IB+i-1,JB+j-1) = A(IA+i-1,JA+j-1), 1<=i<=j, 1<=j<=N; if UPLO = ’L’, B(IB+i-1,JB+j-1) = A(IA+i-1,JA+j-1), j<=i<=M, 1<=j<=N; otherwise, B(IB+i-1,JB+j-1) = A(IA+i-1,JA+j-1), 1<=i<=M, 1<=j<=N.

IB (global input) INTEGER
  The row index in the global array B indicating the first row of sub( B ).
JB (global input) INTEGER
  The column index in the global array B indicating the first column of sub( B ).
DESCB (global and local input) INTEGER array of dimension DLEN_.
  The array descriptor for the distributed matrix B.
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ScaLAPACK version 1.7 PSLACP2 (l) 13 August 2001

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