dsttrf(3P) Sun Performance Library dsttrf(3P)NAMEdsttrf - compute the factorization of a symmetric tridiagonal matrix A
using the Bunch-Kaufman diagonal pivoting method
SYNOPSIS
SUBROUTINE DSTTRF(N, L, D, SUBL, IPIV, INFO)
INTEGER N, INFO
INTEGER IPIV(*)
DOUBLE PRECISION L(*), D(*), SUBL(*)
SUBROUTINE DSTTRF_64(N, L, D, SUBL, IPIV, INFO)
INTEGER*8 N, INFO
INTEGER*8 IPIV(*)
DOUBLE PRECISION L(*), D(*), SUBL(*)
F95 INTERFACE
SUBROUTINE STTRF([N], L, D, SUBL, IPIV, [INFO])
INTEGER :: N, INFO
INTEGER, DIMENSION(:) :: IPIV
REAL(8), DIMENSION(:) :: L, D, SUBL
SUBROUTINE STTRF_64([N], L, D, SUBL, IPIV, [INFO])
INTEGER(8) :: N, INFO
INTEGER(8), DIMENSION(:) :: IPIV
REAL(8), DIMENSION(:) :: L, D, SUBL
C INTERFACE
#include <sunperf.h>
void dsttrf(int n, double *l, double *d, double *subl, int *ipiv, int
*info);
void dsttrf_64(long n, double *l, double *d, double *subl, long *ipiv,
long *info);
PURPOSEdsttrf computes the L*D*L' factorization of a real symmetric tridiago‐
nal matrix A using the Bunch-Kaufman diagonal pivoting method.
ARGUMENTS
N (input)
INTEGER
The order of the matrix A. N >= 0.
L (input/output)
REAL array, dimension (N-1)
On entry, the n-1 subdiagonal elements of the tridiagonal
matrix A. On exit, part of the factorization of A.
D (input/output)
REAL 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*L**H factorization of A.
SUBL (output)
REAL array, dimension (N-2)
On exit, part of the factorization of A.
IPIV (output)
INTEGER array, dimension (N)
Details of the interchanges and block pivot. If IPIV(K) > 0,
1 by 1 pivot, and if IPIV(K) = K + 1 an interchange done; If
IPIV(K) < 0, 2 by 2 pivot, no interchange required.
INFO (output)
INTEGER
= 0: successful exit
< 0: if INFO = -i, the i-th argument had an illegal value
> 0: if INFO = i, D(k,k) is exactly zero. The factorization
has been completed, but the block diagonal matrix D is
exactly singular and division by zero will occur if it is
used to solve a system of equations.
6 Mar 2009 dsttrf(3P)
