version 1.5, 2010/08/07 13:22:24
|
version 1.16, 2017/06/17 10:54:01
|
Line 1
|
Line 1
|
|
*> \brief \b DPTTRF |
|
* |
|
* =========== DOCUMENTATION =========== |
|
* |
|
* Online html documentation available at |
|
* http://www.netlib.org/lapack/explore-html/ |
|
* |
|
*> \htmlonly |
|
*> Download DPTTRF + dependencies |
|
*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/dpttrf.f"> |
|
*> [TGZ]</a> |
|
*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/dpttrf.f"> |
|
*> [ZIP]</a> |
|
*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/dpttrf.f"> |
|
*> [TXT]</a> |
|
*> \endhtmlonly |
|
* |
|
* Definition: |
|
* =========== |
|
* |
|
* SUBROUTINE DPTTRF( N, D, E, INFO ) |
|
* |
|
* .. Scalar Arguments .. |
|
* INTEGER INFO, N |
|
* .. |
|
* .. Array Arguments .. |
|
* DOUBLE PRECISION D( * ), E( * ) |
|
* .. |
|
* |
|
* |
|
*> \par Purpose: |
|
* ============= |
|
*> |
|
*> \verbatim |
|
*> |
|
*> DPTTRF computes the L*D*L**T factorization of a real symmetric |
|
*> positive definite tridiagonal matrix A. The factorization may also |
|
*> be regarded as having the form A = U**T*D*U. |
|
*> \endverbatim |
|
* |
|
* Arguments: |
|
* ========== |
|
* |
|
*> \param[in] N |
|
*> \verbatim |
|
*> N is INTEGER |
|
*> The order of the matrix A. N >= 0. |
|
*> \endverbatim |
|
*> |
|
*> \param[in,out] D |
|
*> \verbatim |
|
*> D is DOUBLE PRECISION array, dimension (N) |
|
*> On entry, the n diagonal elements of the tridiagonal matrix |
|
*> A. On exit, the n diagonal elements of the diagonal matrix |
|
*> D from the L*D*L**T factorization of A. |
|
*> \endverbatim |
|
*> |
|
*> \param[in,out] E |
|
*> \verbatim |
|
*> E is DOUBLE PRECISION array, dimension (N-1) |
|
*> On entry, the (n-1) subdiagonal elements of the tridiagonal |
|
*> matrix A. On exit, the (n-1) subdiagonal elements of the |
|
*> unit bidiagonal factor L from the L*D*L**T factorization of A. |
|
*> E can also be regarded as the superdiagonal of the unit |
|
*> bidiagonal factor U from the U**T*D*U factorization of A. |
|
*> \endverbatim |
|
*> |
|
*> \param[out] INFO |
|
*> \verbatim |
|
*> INFO is INTEGER |
|
*> = 0: successful exit |
|
*> < 0: if INFO = -k, the k-th argument had an illegal value |
|
*> > 0: if INFO = k, the leading minor of order k is not |
|
*> positive definite; if k < N, the factorization could not |
|
*> be completed, while if k = N, the factorization was |
|
*> completed, but D(N) <= 0. |
|
*> \endverbatim |
|
* |
|
* Authors: |
|
* ======== |
|
* |
|
*> \author Univ. of Tennessee |
|
*> \author Univ. of California Berkeley |
|
*> \author Univ. of Colorado Denver |
|
*> \author NAG Ltd. |
|
* |
|
*> \date December 2016 |
|
* |
|
*> \ingroup doublePTcomputational |
|
* |
|
* ===================================================================== |
SUBROUTINE DPTTRF( N, D, E, INFO ) |
SUBROUTINE DPTTRF( N, D, E, INFO ) |
* |
* |
* -- LAPACK routine (version 3.2) -- |
* -- LAPACK computational routine (version 3.7.0) -- |
* -- LAPACK is a software package provided by Univ. of Tennessee, -- |
* -- LAPACK is a software package provided by Univ. of Tennessee, -- |
* -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..-- |
* -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..-- |
* November 2006 |
* December 2016 |
* |
* |
* .. Scalar Arguments .. |
* .. Scalar Arguments .. |
INTEGER INFO, N |
INTEGER INFO, N |
Line 12
|
Line 103
|
DOUBLE PRECISION D( * ), E( * ) |
DOUBLE PRECISION D( * ), E( * ) |
* .. |
* .. |
* |
* |
* Purpose |
|
* ======= |
|
* |
|
* DPTTRF computes the L*D*L' factorization of a real symmetric |
|
* positive definite tridiagonal matrix A. The factorization may also |
|
* be regarded as having the form A = U'*D*U. |
|
* |
|
* Arguments |
|
* ========= |
|
* |
|
* N (input) INTEGER |
|
* The order of the matrix A. N >= 0. |
|
* |
|
* D (input/output) DOUBLE PRECISION array, dimension (N) |
|
* On entry, the n diagonal elements of the tridiagonal matrix |
|
* A. On exit, the n diagonal elements of the diagonal matrix |
|
* D from the L*D*L' factorization of A. |
|
* |
|
* E (input/output) DOUBLE PRECISION array, dimension (N-1) |
|
* On entry, the (n-1) subdiagonal elements of the tridiagonal |
|
* matrix A. On exit, the (n-1) subdiagonal elements of the |
|
* unit bidiagonal factor L from the L*D*L' factorization of A. |
|
* E can also be regarded as the superdiagonal of the unit |
|
* bidiagonal factor U from the U'*D*U factorization of A. |
|
* |
|
* INFO (output) INTEGER |
|
* = 0: successful exit |
|
* < 0: if INFO = -k, the k-th argument had an illegal value |
|
* > 0: if INFO = k, the leading minor of order k is not |
|
* positive definite; if k < N, the factorization could not |
|
* be completed, while if k = N, the factorization was |
|
* completed, but D(N) <= 0. |
|
* |
|
* ===================================================================== |
* ===================================================================== |
* |
* |
* .. Parameters .. |
* .. Parameters .. |
Line 77
|
Line 135
|
IF( N.EQ.0 ) |
IF( N.EQ.0 ) |
$ RETURN |
$ RETURN |
* |
* |
* Compute the L*D*L' (or U'*D*U) factorization of A. |
* Compute the L*D*L**T (or U**T*D*U) factorization of A. |
* |
* |
I4 = MOD( N-1, 4 ) |
I4 = MOD( N-1, 4 ) |
DO 10 I = 1, I4 |
DO 10 I = 1, I4 |