DGTTS2 - solve one of the systems of equations A*X = B or
A'*X = B,
SYNOPSIS
SUBROUTINE DGTTS2( ITRANS, N, NRHS, DL, D, DU, DU2, IPIV,
B, LDB )
INTEGER ITRANS, LDB, N, NRHS
INTEGER IPIV( * )
DOUBLE PRECISION B( LDB, * ), D( * ), DL( * ),
DU( * ), DU2( * )
PURPOSE
DGTTS2 solves one of the systems of equations A*X = B or
A'*X = B, with a tridiagonal matrix A using the LU factor
ization computed by DGTTRF.
ARGUMENTS
ITRANS (input) INTEGER
Specifies the form of the system of equations. =
0: A * X = B (No transpose)
= 1: A'* X = B (Transpose)
= 2: A'* X = B (Conjugate transpose = Transpose)
N (input) INTEGER
The order of the matrix A.
NRHS (input) INTEGER
The number of right hand sides, i.e., the number
of columns of the matrix B. NRHS >= 0.
DL (input) DOUBLE PRECISION array, dimension (N-1)
The (n-1) multipliers that define the matrix L
from the LU factorization of A.
D (input) DOUBLE PRECISION array, dimension (N)
The n diagonal elements of the upper triangular
matrix U from the LU factorization of A.
DU (input) DOUBLE PRECISION array, dimension (N-1)
The (n-1) elements of the first super-diagonal of
U.
DU2 (input) DOUBLE PRECISION array, dimension (N-2)
The (n-2) elements of the second super-diagonal of
U.
IPIV (input) INTEGER array, dimension (N)
The pivot indices; for 1 <= i <= n, row i of the
matrix was interchanged with row IPIV(i). IPIV(i)
cates a row interchange was not required.
B (input/output) DOUBLE PRECISION array,
dimension (LDB,NRHS)
On entry, the matrix of right hand side vectors B.
On exit, B is overwritten by the solution vectors
X.
LDB (input) INTEGER
The leading dimension of the array B. LDB >=
max(1,N).
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