table of contents
PZLAQSY(l) | LAPACK auxiliary routine (version 1.5) | PZLAQSY(l) |
NAME¶
PZLAQSY - equilibrate a symmetric distributed matrix sub( A ) = A(IA:IA+N-1,JA:JA+N-1) using the scaling factors in the vectors SR and SCSYNOPSIS¶
- SUBROUTINE PZLAQSY(
- UPLO, N, A, IA, JA, DESCA, SR, SC, SCOND, AMAX, EQUED )
- CHARACTER
- EQUED, UPLO
- INTEGER
- IA, JA, N
- DOUBLE
- PRECISION AMAX, SCOND
- INTEGER
- DESCA( * )
- DOUBLE
- PRECISION SC( * ), SR( * )
- COMPLEX*16
- A( * )
PURPOSE¶
PZLAQSY equilibrates a symmetric distributed matrix sub( A ) = A(IA:IA+N-1,JA:JA+N-1) using the scaling factors in the vectors SR and SC.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)).
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 whether the upper or lower triangular part of the
symmetric distributed matrix sub( A ) is to be referenced:
- N (global input) INTEGER
- The number of rows and columns to be operated on, i.e. the order of the distributed submatrix sub( A ). N >= 0.
- A (input/output) COMPLEX*16 pointer into the local
- memory to an array of local dimension (LLD_A,LOCc(JA+N-1)).
On entry, the local pieces of the distributed symmetric matrix sub( A ).
If UPLO = 'U', the leading N-by-N upper triangular part of sub( A )
contains the upper triangular part of the matrix, and the strictly lower
triangular part of sub( A ) is not referenced. If UPLO = 'L', the leading
N-by-N lower triangular part of sub( A ) contains the lower triangular
part of the matrix, and the strictly upper trian- gular part of sub( A )
is not referenced. On exit, if EQUED = 'Y', the equilibrated matrix:
- 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.
- SR (local input) DOUBLE PRECISION array, dimension LOCr(M_A)
- The scale factors for A(IA:IA+M-1,JA:JA+N-1). SR is aligned with the distributed matrix A, and replicated across every process column. SR is tied to the distributed matrix A.
- SC (local input) DOUBLE PRECISION array, dimension LOCc(N_A)
- The scale factors for sub( A ). SC is aligned with the dis- tributed matrix A, and replicated down every process row. SC is tied to the distributed matrix A.
- SCOND (global input) DOUBLE PRECISION
- Ratio of the smallest SR(i) (respectively SC(j)) to the largest SR(i) (respectively SC(j)), with IA <= i <= IA+N-1 and JA <= j <= JA+N-1.
- AMAX (global input) DOUBLE PRECISION
- Absolute value of the largest distributed submatrix entry.
- EQUED (output) CHARACTER*1
- Specifies whether or not equilibration was done. = 'N': No
equilibration.
PARAMETERS¶
THRESH is a threshold value used to decide if scaling should be done based on the ratio of the scaling factors. If SCOND < THRESH, scaling is done.12 May 1997 | LAPACK version 1.5 |