LAPACK  3.4.2 LAPACK: Linear Algebra PACKage
spttrf.f File Reference

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## Functions/Subroutines

subroutine spttrf (N, D, E, INFO)
SPTTRF

## Function/Subroutine Documentation

 subroutine spttrf ( integer N, real, dimension( * ) D, real, dimension( * ) E, integer INFO )

SPTTRF

Purpose:
``` SPTTRF 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.```
Parameters:
 [in] N ``` N is INTEGER The order of the matrix A. N >= 0.``` [in,out] D ``` D is REAL 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.``` [in,out] E ``` E is REAL 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.``` [out] INFO ``` 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.```
Date:
November 2011

Definition at line 92 of file spttrf.f.

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