PDORGL2(l) | LAPACK routine (version 1.5) | PDORGL2(l) |
NAME¶
PDORGL2 - generate an M-by-N real distributed matrix Q denoting A(IA:IA+M-1,JA:JA+N-1) with orthonormal rows, which is defined as the first M rows of a product of K elementary reflectors of order N Q = H(k)SYNOPSIS¶
- SUBROUTINE PDORGL2(
- M, N, K, A, IA, JA, DESCA, TAU, WORK, LWORK, INFO )
- INTEGER
- IA, INFO, JA, K, LWORK, M, N
- INTEGER
- DESCA( * )
- DOUBLE
- PRECISION A( * ), TAU( * ), WORK( * )
PURPOSE¶
PDORGL2 generates an M-by-N real distributed matrix Q denoting A(IA:IA+M-1,JA:JA+N-1) with orthonormal rows, which is defined as the first M rows of a product of K elementary reflectors of order NDTYPE_A = 1.
the BLACS process grid A is distribu-
ted over. The context itself is glo-
bal, but the handle (the integer
value) may vary.
array A.
array A.
the rows of the array.
the columns of the array.
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.
array. LLD_A >= MAX(1,LOCr(M_A)).
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¶
- M (global input) INTEGER
- The number of rows to be operated on i.e the number of rows of the distributed submatrix Q. M >= 0.
- N (global input) INTEGER
- The number of columns to be operated on i.e the number of columns of the distributed submatrix Q. N >= M >= 0.
- K (global input) INTEGER
- The number of elementary reflectors whose product defines the matrix Q. M >= K >= 0.
- A (local input/local output) DOUBLE PRECISION pointer into the
- local memory to an array of dimension (LLD_A,LOCc(JA+N-1)). On entry, the i-th row must contain the vector which defines the elementary reflector H(i), IA <= i <= IA+K-1, as returned by PDGELQF in the K rows of its distributed matrix argument A(IA:IA+K-1,JA:*). On exit, this array contains the local pieces of the M-by-N distributed matrix Q.
- 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.
- TAU (local input) DOUBLE PRECISION, array, dimension LOCr(IA+K-1).
- This array contains the scalar factors TAU(i) of the elementary reflectors H(i) as returned by PDGELQF. TAU is tied to the distributed matrix A.
- WORK (local workspace/local output) DOUBLE PRECISION array,
- dimension (LWORK) On exit, WORK(1) returns the minimal and optimal LWORK.
- LWORK (local or global input) INTEGER
- The dimension of the array WORK. LWORK is local input and
must be at least LWORK >= NqA0 + MAX( 1, MpA0 ), where
- INFO (local output) INTEGER
- = 0: successful exit
12 May 1997 | LAPACK version 1.5 |