dpttrf (l)  Linux Man Pages
dpttrf: computes the L*D*Laq factorization of a real symmetric positive definite tridiagonal matrix A
Command to display dpttrf
manual in Linux: $ man l dpttrf
NAME
DPTTRF  computes the L*D*Laq factorization of a real symmetric positive definite tridiagonal matrix A
SYNOPSIS
 SUBROUTINE DPTTRF(

N, D, E, INFO )

INTEGER
INFO, N

DOUBLE
PRECISION D( * ), E( * )
PURPOSE
DPTTRF computes the L*D*Laq factorization of a real symmetric
positive definite tridiagonal matrix A. The factorization may also
be regarded as having the form A = Uaq*D*U.
ARGUMENTS
 N (input) INTEGER

The order of the matrix A. N >= 0.
 D (input/output) DOUBLE PRECISION array, dimension (N)

On entry, the n diagonal elements of the tridiagonal matrix
A. On exit, the n diagonal elements of the diagonal matrix
D from the L*D*Laq factorization of A.
 E (input/output) DOUBLE PRECISION array, dimension (N1)

On entry, the (n1) subdiagonal elements of the tridiagonal
matrix A. On exit, the (n1) subdiagonal elements of the
unit bidiagonal factor L from the L*D*Laq factorization of A.
E can also be regarded as the superdiagonal of the unit
bidiagonal factor U from the Uaq*D*U factorization of A.
 INFO (output) INTEGER

= 0: successful exit
< 0: if INFO = k, the kth argument had an illegal value
> 0: if INFO = k, the leading minor of order k is not
positive definite; if k < N, the factorization could not
be completed, while if k = N, the factorization was
completed, but D(N) <= 0.
Pages related to dpttrf
 dpttrf (3)
 dpttrs (l)  solves a tridiagonal system of the form A * X = B using the L*D*Laq factorization of A computed by DPTTRF
 dptts2 (l)  solves a tridiagonal system of the form A * X = B using the L*D*Laq factorization of A computed by DPTTRF
 dptcon (l)  computes the reciprocal of the condition number (in the 1norm) of a real symmetric positive definite tridiagonal matrix using the factorization A = L*D*L**T or A = U**T*D*U computed by DPTTRF
 dpteqr (l)  computes all eigenvalues and, optionally, eigenvectors of a symmetric positive definite tridiagonal matrix by first factoring the matrix using DPTTRF, and then calling DBDSQR to compute the singular values of the bidiagonal factor
 dptrfs (l)  improves the computed solution to a system of linear equations when the coefficient matrix is symmetric positive definite and tridiagonal, and provides error bounds and backward error estimates for the solution
 dptsv (l)  computes the solution to a real system of linear equations A*X = B, where A is an NbyN symmetric positive definite tridiagonal matrix, and X and B are NbyNRHS matrices
 dptsvx (l)  uses the factorization A = L*D*L**T to compute the solution to a real system of linear equations A*X = B, where A is an NbyN symmetric positive definite tridiagonal matrix and X and B are NbyNRHS matrices