1DPTTRF(1)                LAPACK routine (version 3.2)                DPTTRF(1)
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NAME

6       DPTTRF - computes the L*D*L' factorization of a real symmetric positive
7       definite tridiagonal matrix A
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SYNOPSIS

10       SUBROUTINE DPTTRF( N, D, E, INFO )
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12           INTEGER        INFO, N
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14           DOUBLE         PRECISION D( * ), E( * )
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PURPOSE

17       DPTTRF computes the L*D*L' factorization of a real  symmetric  positive
18       definite  tridiagonal matrix A.  The factorization may also be regarded
19       as having the form A = U'*D*U.
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ARGUMENTS

22       N       (input) INTEGER
23               The order of the matrix A.  N >= 0.
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25       D       (input/output) DOUBLE PRECISION array, dimension (N)
26               On entry, the n diagonal elements of the tridiagonal matrix  A.
27               On  exit, the n diagonal elements of the diagonal matrix D from
28               the L*D*L' factorization of A.
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30       E       (input/output) DOUBLE PRECISION array, dimension (N-1)
31               On entry, the (n-1) subdiagonal  elements  of  the  tridiagonal
32               matrix  A.  On exit, the (n-1) subdiagonal elements of the unit
33               bidiagonal factor L from the L*D*L' factorization of A.  E  can
34               also  be  regarded  as the superdiagonal of the unit bidiagonal
35               factor U from the U'*D*U factorization of A.
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37       INFO    (output) INTEGER
38               = 0: successful exit
39               < 0: if INFO = -k, the k-th argument had an illegal value
40               > 0: if INFO = k, the leading minor of order k is not  positive
41               definite;  if  k < N, the factorization could not be completed,
42               while if k = N, the factorization was completed, but D(N) <= 0.
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46 LAPACK routine (version 3.2)    November 2008                       DPTTRF(1)