All Packages  Class Hierarchy  This Package  Previous  Next  Index

Class org.netlib.lapack.DGTTRF

java.lang.Object
   |
   +----org.netlib.lapack.DGTTRF

public class DGTTRF

extends Object

DGTTRF is a simplified interface to the JLAPACK routine dgttrf.
This interface converts Java-style 2D row-major arrays into
the 1D column-major linearized arrays expected by the lower
level JLAPACK routines.  Using this interface also allows you
to omit offset and leading dimension arguments.  However, because
of these conversions, these routines will be slower than the low
level ones.  Following is the description from the original Fortran
source.  Contact seymour@cs.utk.edu with any questions.

 *     ..
 *
 *  Purpose
 *  =======
 *
 *  DGTTRF computes an LU factorization of a real 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.
 *
 *  Arguments
 *  =========
 *
 *  N       (input) INTEGER
 *          The order of the matrix A.  N >= 0.
 *
 *  DL      (input/output) DOUBLE PRECISION array, dimension (N-1)
 *          On entry, DL must contain the (n-1) subdiagonal 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       (input/output) DOUBLE PRECISION 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      (input/output) DOUBLE PRECISION array, dimension (N-1)
 *          On entry, DU must contain the (n-1) superdiagonal elements
 *          of A.
 *          On exit, DU is overwritten by the (n-1) elements of the first
 *          superdiagonal of U.
 *
 *  DU2     (output) DOUBLE PRECISION array, dimension (N-2)
 *          On exit, DU2 is overwritten by the (n-2) elements of the
 *          second superdiagonal of U.
 *
 *  IPIV    (output) 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    (output) INTEGER
 *          = 0:  successful exit
 *          < 0:  if INFO = -i, the i-th argument had an illegal value
 *          > 0:  if INFO = i, U(i,i) 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.
 *
 *  =====================================================================
 *
 *     .. Local Scalars ..

DGTTRF()

DGTTRF(int, double[], double[], double[], double[], int[], intW)

 public DGTTRF()

 public static void DGTTRF(int n,
                           double dl[],
                           double d[],
                           double du[],
                           double du2[],
                           int ipiv[],
                           intW info)

All Packages  Class Hierarchy  This Package  Previous  Next  Index