PZDTTRF(l) LAPACK routine (version 1.5) PZDTTRF(l)
NAME
PZDTTRF - compute a LU factorization of an N-by-N complex tridiagonal diagonally dominant-like distributed matrix A(1:N, JA:JA+N-1)
SYNOPSIS
SUBROUTINE PZDTTRF( N, DL, D, DU, JA, DESCA, AF, LAF, WORK, LWORK, INFO )
INTEGER INFO, JA, LAF, LWORK, N
INTEGER DESCA( * )
COMPLEX*16 AF( * ), D( * ), DL( * ), DU( * ), WORK( * )
PURPOSE
PZDTTRF computes a LU factorization of an N-by-N complex tridiagonal diagonally dominant-like distributed matrix A(1:N, JA:JA+N-1).
Reordering is used to increase parallelism in the factorization. This reordering results in factors that are DIFFERENT from those produced
by equivalent sequential codes. These factors cannot be used directly by users; however, they can be used in
subsequent calls to PZDTTRS to solve linear systems.
The factorization has the form
P A(1:N, JA:JA+N-1) P^T = L U
where U is a tridiagonal upper triangular matrix and L is tridiagonal lower triangular, and P is a permutation matrix.
LAPACK version 1.5 12 May 1997 PZDTTRF(l)
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DDTTRF(l) LAPACK routine (version 2.0) DDTTRF(l)
NAME
DDTTRF - compute an LU factorization of a complex tridiagonal matrix A using elimination without partial pivoting
SYNOPSIS
SUBROUTINE DDTTRF( N, DL, D, DU, INFO )
INTEGER INFO, N
DOUBLE PRECISION D( * ), DL( * ), DU( * )
PURPOSE
DDTTRF computes an LU factorization of a complex tridiagonal matrix A using elimination without partial pivoting.
The factorization has the form
A = L * U
where L is a product of unit lower bidiagonal
matrices and U is upper triangular with nonzeros in only the main diagonal and first superdiagonal.
ARGUMENTS
N (input) INTEGER
The order of the matrix A. N >= 0.
DL (input/output) COMPLEX array, dimension (N-1)
On entry, DL must contain the (n-1) subdiagonal elements of A. On exit, DL is overwritten by the (n-1) multipliers that define the
matrix L from the LU factorization of A.
D (input/output) COMPLEX array, dimension (N)
On entry, D must contain the diagonal elements of A. On exit, D is overwritten by the n diagonal elements of the upper triangular
matrix U from the LU factorization of A.
DU (input/output) COMPLEX array, dimension (N-1)
On entry, DU must contain the (n-1) superdiagonal elements of A. On exit, DU is overwritten by the (n-1) elements of the first
superdiagonal of U.
INFO (output) INTEGER
= 0: successful exit
< 0: if INFO = -i, the i-th argument had an illegal value
> 0: if INFO = i, U(i,i) is exactly zero. The factorization has been completed, but the factor U is exactly singular, and division
by zero will occur if it is used to solve a system of equations.
modified LAPACK routine 12 May 1997 DDTTRF(l)
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