cgttrf(3)

NAME

cgttrf.f –

SYNOPSIS

Functions/Subroutines

subroutine cgttrf (N, DL, D, DU, DU2, IPIV, INFO)
CGTTRF

Function/Subroutine Documentation

subroutine cgttrf (integerN, complex, dimension( * )DL, complex, dimension( * )D, complex, dimension( * )DU, complex, dimension( * )DU2, integer, dimension( * )IPIV, integerINFO)

CGTTRF

Purpose:

 CGTTRF computes an LU factorization of a complex tridiagonal matrix A
 using elimination with partial pivoting and row interchanges.
 The factorization has the form
    A = L * U
 where L is a product of permutation and unit lower bidiagonal
 matrices and U is upper triangular with nonzeros in only the main
 diagonal and first two superdiagonals.

 

Parameters:

N

          N is INTEGER
          The order of the matrix A.

DL

          DL is COMPLEX array, dimension (N-1)
          On entry, DL must contain the (n-1) sub-diagonal elements of
          A.
          On exit, DL is overwritten by the (n-1) multipliers that
          define the matrix L from the LU factorization of A.

D

          D is COMPLEX array, dimension (N)
          On entry, D must contain the diagonal elements of A.
          On exit, D is overwritten by the n diagonal elements of the
          upper triangular matrix U from the LU factorization of A.

DU

          DU is COMPLEX array, dimension (N-1)
          On entry, DU must contain the (n-1) super-diagonal elements
          of A.
          On exit, DU is overwritten by the (n-1) elements of the first
          super-diagonal of U.

DU2

          DU2 is COMPLEX array, dimension (N-2)
          On exit, DU2 is overwritten by the (n-2) elements of the
          second super-diagonal of U.

IPIV

IPIV is 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.

INFO

          INFO is INTEGER
          = 0:  successful exit
          < 0:  if INFO = -k, the k-th argument had an illegal value
          > 0:  if INFO = k, U(k,k) is exactly zero. The factorization
                has been completed, but the factor U is exactly
                singular, and division by zero will occur if it is used
                to solve a system of equations.

 

Author:

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Date:

September 2012

Definition at line 125 of file cgttrf.f.

Author

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