PZLACP2 - copie all or part of a distributed matrix A to another distributed
matrix B
- SUBROUTINE PZLACP2(
- UPLO, M, N, A, IA, JA, DESCA, B, IB, JB, DESCB )
CHARACTER UPLO INTEGER IA, IB, JA, JB, M, N INTEGER DESCA( * ), DESCB( * )
COMPLEX*16 A( * ), B( * )
PZLACP2 copies all or part of a distributed matrix A to another distributed
matrix B. No communication is performed, PZLACP2 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). PZLACP2 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
- 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) COMPLEX*16 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) COMPLEX*16 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.