PDLAPV2(l) | LAPACK auxiliary routine (version 1.5) | PDLAPV2(l) |
NAME¶
PDLAPV2 - applie either P (permutation matrix indicated by IPIV) or inv( P ) to a M-by-N distributed matrix sub( A ) denoting A(IA:IA+M-1,JA:JA+N-1), resulting in row or column pivotingSYNOPSIS¶
- SUBROUTINE PDLAPV2(
- DIREC, ROWCOL, M, N, A, IA, JA, DESCA, IPIV,IP, JP, DESCIP )
PURPOSE¶
PDLAPV2 applies either P (permutation matrix indicated by IPIV) or inv( P ) to a M-by-N distributed matrix sub( A ) denoting A(IA:IA+M-1,JA:JA+N-1), resulting in row or column pivoting. The pivot vector should be aligned with the distributed matrix A. For pivoting the rows of sub( A ), IPIV should be distributed along a process column and replicated over all process rows. Similarly, IPIV should be distributed along a process row and replicated over all process columns for column pivoting.DTYPE_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)). 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( 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¶
- DIREC (global input) CHARACTER
- Specifies in which order the permutation is applied:= 'F' (Forward) Applies pivots Forward from top of matrix. Computes P * sub( A ); = 'B' (Backward) Applies pivots Backward from bottom of matrix. Computes inv( P ) * sub( A ).
- ROWCOL (global input) CHARACTER
- Specifies if the rows or columns are to be permuted:= 'R' Rows will be permuted, = 'C' Columns will be permuted.
- M (global input) INTEGER
- The number of rows to be operated on, i.e. the number of rowsof the distributed submatrix sub( A ). M >= 0.
- N (global input) INTEGER
- The number of columns to be operated on, i.e. the number ofcolumns of the distributed submatrix sub( A ). N >= 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, this local array contains the local pieces of the distributed matrix sub( A ) to which the row or columns interchanges will be applied. On exit, this array contains the local pieces of the permuted distributed matrix.
- IA (global input) INTEGER
- The row index in the global array A indicating the firstrow of sub( A ).
- JA (global input) INTEGER
- The column index in the global array A indicating thefirst column of sub( A ).
- DESCA (global and local input) INTEGER array of dimension DLEN_.
- The array descriptor for the distributed matrix A.
- IPIV (input) INTEGER array, dimension >= LOCr(M_A)+MB_A if
- ROWCOL = 'R', LOCc(N_A)+NB_A otherwise. It containsthe pivoting information. IPIV(i) is the global row (column), local row (column) i was swapped with. The last piece of the array of size MB_A (resp. NB_A) is used as workspace. IPIV is tied to the distributed matrix A.
- IP (global input) INTEGER
- IPIV's global row index, which points to the beginning of thesubmatrix which is to be operated on.
- JP (global input) INTEGER
- IPIV's global column index, which points to the beginning ofthe submatrix which is to be operated on.
- DESCIP (global and local input) INTEGER array of dimension 8
- The array descriptor for the distributed matrix IPIV.
12 May 1997 | LAPACK version 1.5 |