cgttrf-f(3)

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 is INTEGER
 The order of the matrix A.

 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 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 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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