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---
:name: dpttrf
:md5sum: 203e7bbfdbd7f2634ace2a157d4cb178
:category: :subroutine
:arguments:
- n:
:type: integer
:intent: input
- d:
:type: doublereal
:intent: input/output
:dims:
- n
- e:
:type: doublereal
:intent: input/output
:dims:
- n-1
- info:
:type: integer
:intent: output
:substitutions: {}
:fortran_help: " SUBROUTINE DPTTRF( N, D, E, INFO )\n\n\
* Purpose\n\
* =======\n\
*\n\
* DPTTRF computes the L*D*L' factorization of a real symmetric\n\
* positive definite tridiagonal matrix A. The factorization may also\n\
* be regarded as having the form A = U'*D*U.\n\
*\n\n\
* Arguments\n\
* =========\n\
*\n\
* N (input) INTEGER\n\
* The order of the matrix A. N >= 0.\n\
*\n\
* D (input/output) DOUBLE PRECISION array, dimension (N)\n\
* On entry, the n diagonal elements of the tridiagonal matrix\n\
* A. On exit, the n diagonal elements of the diagonal matrix\n\
* D from the L*D*L' factorization of A.\n\
*\n\
* E (input/output) DOUBLE PRECISION array, dimension (N-1)\n\
* On entry, the (n-1) subdiagonal elements of the tridiagonal\n\
* matrix A. On exit, the (n-1) subdiagonal elements of the\n\
* unit bidiagonal factor L from the L*D*L' factorization of A.\n\
* E can also be regarded as the superdiagonal of the unit\n\
* bidiagonal factor U from the U'*D*U factorization of A.\n\
*\n\
* INFO (output) INTEGER\n\
* = 0: successful exit\n\
* < 0: if INFO = -k, the k-th argument had an illegal value\n\
* > 0: if INFO = k, the leading minor of order k is not\n\
* positive definite; if k < N, the factorization could not\n\
* be completed, while if k = N, the factorization was\n\
* completed, but D(N) <= 0.\n\
*\n\n\
* =====================================================================\n\
*\n"
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