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---
:name: dsterf
:md5sum: 5dc7d5e9f4d5a3a72037d3b60fce2589
: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 DSTERF( N, D, E, INFO )\n\n\
* Purpose\n\
* =======\n\
*\n\
* DSTERF computes all eigenvalues of a symmetric tridiagonal matrix\n\
* using the Pal-Walker-Kahan variant of the QL or QR algorithm.\n\
*\n\n\
* Arguments\n\
* =========\n\
*\n\
* N (input) INTEGER\n\
* The order of the matrix. N >= 0.\n\
*\n\
* D (input/output) DOUBLE PRECISION array, dimension (N)\n\
* On entry, the n diagonal elements of the tridiagonal matrix.\n\
* On exit, if INFO = 0, the eigenvalues in ascending order.\n\
*\n\
* E (input/output) DOUBLE PRECISION array, dimension (N-1)\n\
* On entry, the (n-1) subdiagonal elements of the tridiagonal\n\
* matrix.\n\
* On exit, E has been destroyed.\n\
*\n\
* INFO (output) INTEGER\n\
* = 0: successful exit\n\
* < 0: if INFO = -i, the i-th argument had an illegal value\n\
* > 0: the algorithm failed to find all of the eigenvalues in\n\
* a total of 30*N iterations; if INFO = i, then i\n\
* elements of E have not converged to zero.\n\
*\n\n\
* =====================================================================\n\
*\n"
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