DGTTS2(3S)DGTTS2(3S)NAMEDGTTS2 - 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(
* )
IMPLEMENTATION
These routines are part of the SCSL Scientific Library and can be loaded
using either the -lscs or the -lscs_mp option. The -lscs_mp option
directs the linker to use the multi-processor version of the library.
When linking to SCSL with -lscs or -lscs_mp, the default integer size is
4 bytes (32 bits). Another version of SCSL is available in which integers
are 8 bytes (64 bits). This version allows the user access to larger
memory sizes and helps when porting legacy Cray codes. It can be loaded
by using the -lscs_i8 option or the -lscs_i8_mp option. A program may use
only one of the two versions; 4-byte integer and 8-byte integer library
calls cannot be mixed.
PURPOSEDGTTS2 solves one of the systems of equations A*X = B or A'*X = B, with a
tridiagonal matrix A using the LU factorization 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.
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DGTTS2(3S)DGTTS2(3S)
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) will always be either i
or i+1; IPIV(i) = i indicates 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).
SEE ALSOINTRO_LAPACK(3S), INTRO_SCSL(3S)
This man page is available only online.
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