PSPOTRS(l) | LAPACK routine (version 1.5) | PSPOTRS(l) |
NAME¶
PSPOTRS - solve a system of linear equations sub( A ) * X = sub( B ) A(IA:IA+N-1,JA:JA+N-1)*X = B(IB:IB+N-1,JB:JB+NRHS-1)SYNOPSIS¶
- SUBROUTINE PSPOTRS(
- UPLO, N, NRHS, A, IA, JA, DESCA, B, IB, JB, DESCB, INFO )
PURPOSE¶
PSPOTRS solves a system of linear equations where sub( A ) denotes A(IA:IA+N-1,JA:JA+N-1) and is a N-by-N symmetric positive definite distributed matrix using the Cholesky factorization sub( A ) = U**T*U or L*L**T computed by PSPOTRF. sub( B ) denotes the distributed matrix B(IB:IB+N-1,JB:JB+NRHS-1). NotesDTYPE_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¶
- UPLO (global input) CHARACTER
- = 'U': Upper triangle of sub( A ) is stored;
- 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.
- NRHS (global input) INTEGER
- The number of right hand sides, i.e., the number of columns of the distributed submatrix sub( B ). NRHS >= 0.
- A (local input) REAL pointer into local memory to
- an array of dimension (LLD_A, LOCc(JA+N-1)). On entry, this array contains the factors L or U from the Cholesky facto- rization sub( A ) = L*L**T or U**T*U, as computed by PSPOTRF.
- 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 input/local output) REAL pointer into the
- local memory to an array of local dimension (LLD_B,LOCc(JB+NRHS-1)). On entry, this array contains the the local pieces of the right hand sides sub( B ). On exit, this array contains the local pieces of the solution distributed matrix X.
- 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.
- INFO (global output) INTEGER
- = 0: successful exit
12 May 1997 | LAPACK version 1.5 |