Dpttrs.f -
subroutine dpttrs (N, NRHS, D, E, B, LDB, INFO)
DPTTRS
DPTTRS
Purpose:
DPTTRS solves a tridiagonal system of the form
A * X = B
using the L*D*L**T factorization of A computed by DPTTRF. D is a
diagonal matrix specified in the vector D, L is a unit bidiagonal
matrix whose subdiagonal is specified in the vector E, and X and B
are N by NRHS matrices.
Parameters:
N
N is INTEGER
The order of the tridiagonal matrix A. N >= 0.
NRHS
NRHS is INTEGER
The number of right hand sides, i.e., the number of columns
of the matrix B. NRHS >= 0.
D
D is DOUBLE PRECISION array, dimension (N)
The n diagonal elements of the diagonal matrix D from the
L*D*L**T factorization of A.
E
E is DOUBLE PRECISION array, dimension (N-1)
The (n-1) subdiagonal 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 bidiagonal factor U from the
factorization A = U**T*D*U.
B
B is DOUBLE PRECISION array, dimension (LDB,NRHS)
On entry, the right hand side vectors B for the system of
linear equations.
On exit, the solution vectors, X.
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.
Date:
September 2012
Definition at line 110 of file dpttrs.f.
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