dlavsy.f - Man Page
TESTING/LIN/dlavsy.f
Synopsis
Functions/Subroutines
subroutine dlavsy (uplo, trans, diag, n, nrhs, a, lda, ipiv, b, ldb, info)
DLAVSY
Function/Subroutine Documentation
subroutine dlavsy (character uplo, character trans, character diag, integer n, integer nrhs, double precision, dimension( lda, * ) a, integer lda, integer, dimension( * ) ipiv, double precision, dimension( ldb, * ) b, integer ldb, integer info)
DLAVSY
Purpose:
DLAVSY performs one of the matrix-vector operations x := A*x or x := A'*x, where x is an N element vector and A is one of the factors from the block U*D*U' or L*D*L' factorization computed by DSYTRF. If TRANS = 'N', multiplies by U or U * D (or L or L * D) If TRANS = 'T', multiplies by U' or D * U' (or L' or D * L') If TRANS = 'C', multiplies by U' or D * U' (or L' or D * L')
- Parameters
UPLO
UPLO is CHARACTER*1 Specifies whether the factor stored in A is upper or lower triangular. = 'U': Upper triangular = 'L': Lower triangular
TRANS
TRANS is CHARACTER*1 Specifies the operation to be performed: = 'N': x := A*x = 'T': x := A'*x = 'C': x := A'*x
DIAG
DIAG is CHARACTER*1 Specifies whether or not the diagonal blocks are unit matrices. If the diagonal blocks are assumed to be unit, then A = U or A = L, otherwise A = U*D or A = L*D. = 'U': Diagonal blocks are assumed to be unit matrices. = 'N': Diagonal blocks are assumed to be non-unit matrices.
N
N is INTEGER The number of rows and columns of the matrix A. N >= 0.
NRHS
NRHS is INTEGER The number of right hand sides, i.e., the number of vectors x to be multiplied by A. NRHS >= 0.
A
A is DOUBLE PRECISION array, dimension (LDA,N) The block diagonal matrix D and the multipliers used to obtain the factor U or L as computed by DSYTRF. Stored as a 2-D triangular matrix.
LDA
LDA is INTEGER The leading dimension of the array A. LDA >= max(1,N).
IPIV
IPIV is INTEGER array, dimension (N) Details of the interchanges and the block structure of D, as determined by DSYTRF. If UPLO = 'U': If IPIV(k) > 0, then rows and columns k and IPIV(k) were interchanged and D(k,k) is a 1-by-1 diagonal block. (If IPIV( k ) = k, no interchange was done). If IPIV(k) = IPIV(k-1) < 0, then rows and columns k-1 and -IPIV(k) were interchanged, D(k-1:k,k-1:k) is a 2-by-2 diagonal block. If UPLO = 'L': If IPIV(k) > 0, then rows and columns k and IPIV(k) were interchanged and D(k,k) is a 1-by-1 diagonal block. (If IPIV( k ) = k, no interchange was done). If IPIV(k) = IPIV(k+1) < 0, then rows and columns k+1 and -IPIV(k) were interchanged, D(k:k+1,k:k+1) is a 2-by-2 diagonal block.
B
B is DOUBLE PRECISION array, dimension (LDB,NRHS) On entry, B contains NRHS vectors of length N. On exit, B is overwritten with the product A * B.
LDB
LDB is INTEGER The leading dimension of the array B. LDB >= max(1,N).
INFO
INFO is INTEGER = 0: successful exit < 0: if INFO = -k, the k-th argument had an illegal value
- Author
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Definition at line 153 of file dlavsy.f.
Author
Generated automatically by Doxygen for LAPACK from the source code.
Referenced By
The man page dlavsy(3) is an alias of dlavsy.f(3).
Tue Nov 28 2023 12:08:43 Version 3.12.0 LAPACK