SPTSV - compute the solution to a real system of linear
equations A*X = B, where A is an N-by-N symmetric positive
definite tridiagonal matrix, and X and B are N-by-NRHS
matrices
SYNOPSIS
SUBROUTINE SPTSV( N, NRHS, D, E, B, LDB, INFO )
INTEGER INFO, LDB, N, NRHS
REAL B( LDB, * ), D( * ), E( * )
PURPOSE
SPTSV computes the solution to a real system of linear
equations A*X = B, where A is an N-by-N symmetric positive
definite tridiagonal matrix, and X and B are N-by-NRHS
matrices. A is factored as A = L*D*L**T, and the factored
form of A is then used to solve the system of equations.
ARGUMENTS
N (input) INTEGER
The order of the matrix A. N >= 0.
NRHS (input) INTEGER
The number of right hand sides, i.e., the number
of columns of the matrix B. NRHS >= 0.
D (input/output) REAL array, dimension (N)
On entry, the n diagonal elements of the tridiago
nal matrix A. On exit, the n diagonal elements of
the diagonal matrix D from the factorization A =
L*D*L**T.
E (input/output) REAL array, dimension (N-1)
On entry, the (n-1) subdiagonal elements of the
tridiagonal matrix A. On exit, the (n-1) subdiag
onal elements of the unit bidiagonal factor L from
the L*D*L**T factorization of A. (E can also be
regarded as the superdiagonal of the unit bidiago
nal factor U from the U**T*D*U factorization of
A.)
B (input/output) REAL array, dimension (LDB,NRHS)
On entry, the N-by-NRHS right hand side matrix B.
On exit, if INFO = 0, the N-by-NRHS solution
matrix X.
LDB (input) INTEGER
The leading dimension of the array B. LDB >=
max(1,N).
= 0: successful exit
< 0: if INFO = -i, the i-th argument had an ille
gal value
> 0: if INFO = i, the leading minor of order i is
not positive definite, and the solution has not
been computed. The factorization has not been
completed unless i = N.
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