version 1.7, 2010/12/21 13:53:37
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version 1.8, 2011/07/22 07:38:10
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SUBROUTINE DPTTRF( N, D, E, INFO ) |
SUBROUTINE DPTTRF( N, D, E, INFO ) |
* |
* |
* -- LAPACK routine (version 3.2) -- |
* -- LAPACK routine (version 3.3.1) -- |
* -- 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 |
* -- April 2011 -- |
* |
* |
* .. Scalar Arguments .. |
* .. Scalar Arguments .. |
INTEGER INFO, N |
INTEGER INFO, N |
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* Purpose |
* Purpose |
* ======= |
* ======= |
* |
* |
* DPTTRF computes the L*D*L' factorization of a real symmetric |
* DPTTRF computes the L*D*L**T factorization of a real symmetric |
* positive definite tridiagonal matrix A. The factorization may also |
* positive definite tridiagonal matrix A. The factorization may also |
* be regarded as having the form A = U'*D*U. |
* be regarded as having the form A = U**T*D*U. |
* |
* |
* Arguments |
* Arguments |
* ========= |
* ========= |
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* D (input/output) DOUBLE PRECISION array, dimension (N) |
* D (input/output) DOUBLE PRECISION array, dimension (N) |
* On entry, the n diagonal elements of the tridiagonal matrix |
* On entry, the n diagonal elements of the tridiagonal matrix |
* A. On exit, the n diagonal elements of the diagonal matrix |
* A. On exit, the n diagonal elements of the diagonal matrix |
* D from the L*D*L' factorization of A. |
* D from the L*D*L**T factorization of A. |
* |
* |
* E (input/output) DOUBLE PRECISION array, dimension (N-1) |
* E (input/output) DOUBLE PRECISION array, dimension (N-1) |
* On entry, the (n-1) subdiagonal elements of the tridiagonal |
* On entry, the (n-1) subdiagonal elements of the tridiagonal |
* matrix A. On exit, the (n-1) subdiagonal elements of the |
* matrix A. On exit, the (n-1) subdiagonal elements of the |
* unit bidiagonal factor L from the L*D*L' factorization of A. |
* unit bidiagonal factor L from the L*D*L**T factorization of A. |
* E can also be regarded as the superdiagonal of the unit |
* E can also be regarded as the superdiagonal of the unit |
* bidiagonal factor U from the U'*D*U factorization of A. |
* bidiagonal factor U from the U**T*D*U factorization of A. |
* |
* |
* INFO (output) INTEGER |
* INFO (output) INTEGER |
* = 0: successful exit |
* = 0: successful exit |
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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 |