dgttrs (l) - Linux Manuals

dgttrs: solves one of the systems of equations A*X = B or Aaq*X = B,

NAME

DGTTRS - solves one of the systems of equations A*X = B or Aaq*X = B,

SYNOPSIS

SUBROUTINE DGTTRS(
TRANS, N, NRHS, DL, D, DU, DU2, IPIV, B, LDB, INFO )

    
CHARACTER TRANS

    
INTEGER INFO, LDB, N, NRHS

    
INTEGER IPIV( * )

    
DOUBLE PRECISION B( LDB, * ), D( * ), DL( * ), DU( * ), DU2( * )

PURPOSE

DGTTRS solves one of the systems of equations
A*X = B  or  Aaq*X = B, with a tridiagonal matrix A using the LU factorization computed by DGTTRF.

ARGUMENTS

TRANS (input) CHARACTER*1
Specifies the form of the system of equations. = aqNaq: A * X = B (No transpose)
= aqTaq: Aaq* X = B (Transpose)
= aqCaq: Aaq* 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) 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).
INFO (output) INTEGER
= 0: successful exit
< 0: if INFO = -i, the i-th argument had an illegal value

Pages related to dgttrs

  • dgttrs (3)
  • dgttrf (l) - computes an LU factorization of a real tridiagonal matrix A using elimination with partial pivoting and row interchanges
  • dgtts2 (l) - solves one of the systems of equations A*X = B or Aaq*X = B,
  • dgtcon (l) - estimates the reciprocal of the condition number of a real tridiagonal matrix A using the LU factorization as computed by DGTTRF
  • dgtrfs (l) - improves the computed solution to a system of linear equations when the coefficient matrix is tridiagonal, and provides error bounds and backward error estimates for the solution
  • dgtsv (l) - solves the equation A*X = B,
  • dgtsvx (l) - uses the LU factorization to compute the solution to a real system of linear equations A * X = B or A**T * X = B,
  • dgbbrd (l) - reduces a real general m-by-n band matrix A to upper bidiagonal form B by an orthogonal transformation