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---
:name: dstev
:md5sum: 2f4d636a27f6e1a3441dbd47afa973cb
:category: :subroutine
:arguments:
- jobz:
:type: char
:intent: input
- n:
:type: integer
:intent: input
- d:
:type: doublereal
:intent: input/output
:dims:
- n
- e:
:type: doublereal
:intent: input/output
:dims:
- n-1
- z:
:type: doublereal
:intent: output
:dims:
- ldz
- n
- ldz:
:type: integer
:intent: input
- work:
:type: doublereal
:intent: workspace
:dims:
- "lsame_(&jobz,\"N\") ? 0 : MAX(1,2*n-2)"
- info:
:type: integer
:intent: output
:substitutions:
ldz: "lsame_(&jobz,\"V\") ? MAX(1,n) : 1"
:fortran_help: " SUBROUTINE DSTEV( JOBZ, N, D, E, Z, LDZ, WORK, INFO )\n\n\
* Purpose\n\
* =======\n\
*\n\
* DSTEV computes all eigenvalues and, optionally, eigenvectors of a\n\
* real symmetric tridiagonal matrix A.\n\
*\n\n\
* Arguments\n\
* =========\n\
*\n\
* JOBZ (input) CHARACTER*1\n\
* = 'N': Compute eigenvalues only;\n\
* = 'V': Compute eigenvalues and eigenvectors.\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\
* A.\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 A, stored in elements 1 to N-1 of E.\n\
* On exit, the contents of E are destroyed.\n\
*\n\
* Z (output) DOUBLE PRECISION array, dimension (LDZ, N)\n\
* If JOBZ = 'V', then if INFO = 0, Z contains the orthonormal\n\
* eigenvectors of the matrix A, with the i-th column of Z\n\
* holding the eigenvector associated with D(i).\n\
* If JOBZ = 'N', then Z is not referenced.\n\
*\n\
* LDZ (input) INTEGER\n\
* The leading dimension of the array Z. LDZ >= 1, and if\n\
* JOBZ = 'V', LDZ >= max(1,N).\n\
*\n\
* WORK (workspace) DOUBLE PRECISION array, dimension (max(1,2*N-2))\n\
* If JOBZ = 'N', WORK is not referenced.\n\
*\n\
* INFO (output) INTEGER\n\
* = 0: successful exit\n\
* < 0: if INFO = -i, the i-th argument had an illegal value\n\
* > 0: if INFO = i, the algorithm failed to converge; i\n\
* off-diagonal elements of E did not converge to zero.\n\
*\n\n\
* =====================================================================\n\
*\n"
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