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---
:name: ssyevd
:md5sum: e10c9634d1a916940bd4f1bd51d00aed
:category: :subroutine
:arguments:
- jobz:
:type: char
:intent: input
- uplo:
:type: char
:intent: input
- n:
:type: integer
:intent: input
- a:
:type: real
:intent: input/output
:dims:
- lda
- n
- lda:
:type: integer
:intent: input
- w:
:type: real
:intent: output
:dims:
- n
- work:
:type: real
:intent: output
:dims:
- MAX(1,lwork)
- lwork:
:type: integer
:intent: input
:option: true
:default: "n<=1 ? 1 : lsame_(&jobz,\"N\") ? 2*n+1 : lsame_(&jobz,\"V\") ? 1+6*n+2*n*n : 0"
- iwork:
:type: integer
:intent: output
:dims:
- MAX(1,liwork)
- liwork:
:type: integer
:intent: input
:option: true
:default: "n<=1 ? 1 : lsame_(&jobz,\"N\") ? 1 : lsame_(&jobz,\"V\") ? 3+5*n : 0"
- info:
:type: integer
:intent: output
:substitutions: {}
:fortran_help: " SUBROUTINE SSYEVD( JOBZ, UPLO, N, A, LDA, W, WORK, LWORK, IWORK, LIWORK, INFO )\n\n\
* Purpose\n\
* =======\n\
*\n\
* SSYEVD computes all eigenvalues and, optionally, eigenvectors of a\n\
* real symmetric matrix A. If eigenvectors are desired, it uses a\n\
* divide and conquer algorithm.\n\
*\n\
* The divide and conquer algorithm makes very mild assumptions about\n\
* floating point arithmetic. It will work on machines with a guard\n\
* digit in add/subtract, or on those binary machines without guard\n\
* digits which subtract like the Cray X-MP, Cray Y-MP, Cray C-90, or\n\
* Cray-2. It could conceivably fail on hexadecimal or decimal machines\n\
* without guard digits, but we know of none.\n\
*\n\
* Because of large use of BLAS of level 3, SSYEVD needs N**2 more\n\
* workspace than SSYEVX.\n\
*\n\n\
* Arguments\n\
* =========\n\
*\n\
* JOBZ (input) CHARACTER*1\n\
* = 'N': Compute eigenvalues only;\n\
* = 'V': Compute eigenvalues and eigenvectors.\n\
*\n\
* UPLO (input) CHARACTER*1\n\
* = 'U': Upper triangle of A is stored;\n\
* = 'L': Lower triangle of A is stored.\n\
*\n\
* N (input) INTEGER\n\
* The order of the matrix A. N >= 0.\n\
*\n\
* A (input/output) REAL array, dimension (LDA, N)\n\
* On entry, the symmetric matrix A. If UPLO = 'U', the\n\
* leading N-by-N upper triangular part of A contains the\n\
* upper triangular part of the matrix A. If UPLO = 'L',\n\
* the leading N-by-N lower triangular part of A contains\n\
* the lower triangular part of the matrix A.\n\
* On exit, if JOBZ = 'V', then if INFO = 0, A contains the\n\
* orthonormal eigenvectors of the matrix A.\n\
* If JOBZ = 'N', then on exit the lower triangle (if UPLO='L')\n\
* or the upper triangle (if UPLO='U') of A, including the\n\
* diagonal, is destroyed.\n\
*\n\
* LDA (input) INTEGER\n\
* The leading dimension of the array A. LDA >= max(1,N).\n\
*\n\
* W (output) REAL array, dimension (N)\n\
* If INFO = 0, the eigenvalues in ascending order.\n\
*\n\
* WORK (workspace/output) REAL array,\n\
* dimension (LWORK)\n\
* On exit, if INFO = 0, WORK(1) returns the optimal LWORK.\n\
*\n\
* LWORK (input) INTEGER\n\
* The dimension of the array WORK.\n\
* If N <= 1, LWORK must be at least 1.\n\
* If JOBZ = 'N' and N > 1, LWORK must be at least 2*N+1.\n\
* If JOBZ = 'V' and N > 1, LWORK must be at least \n\
* 1 + 6*N + 2*N**2.\n\
*\n\
* If LWORK = -1, then a workspace query is assumed; the routine\n\
* only calculates the optimal sizes of the WORK and IWORK\n\
* arrays, returns these values as the first entries of the WORK\n\
* and IWORK arrays, and no error message related to LWORK or\n\
* LIWORK is issued by XERBLA.\n\
*\n\
* IWORK (workspace/output) INTEGER array, dimension (MAX(1,LIWORK))\n\
* On exit, if INFO = 0, IWORK(1) returns the optimal LIWORK.\n\
*\n\
* LIWORK (input) INTEGER\n\
* The dimension of the array IWORK.\n\
* If N <= 1, LIWORK must be at least 1.\n\
* If JOBZ = 'N' and N > 1, LIWORK must be at least 1.\n\
* If JOBZ = 'V' and N > 1, LIWORK must be at least 3 + 5*N.\n\
*\n\
* If LIWORK = -1, then a workspace query is assumed; the\n\
* routine only calculates the optimal sizes of the WORK and\n\
* IWORK arrays, returns these values as the first entries of\n\
* the WORK and IWORK arrays, and no error message related to\n\
* LWORK or LIWORK is issued by XERBLA.\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 and JOBZ = 'N', then the algorithm failed\n\
* to converge; i off-diagonal elements of an intermediate\n\
* tridiagonal form did not converge to zero;\n\
* if INFO = i and JOBZ = 'V', then the algorithm failed\n\
* to compute an eigenvalue while working on the submatrix\n\
* lying in rows and columns INFO/(N+1) through\n\
* mod(INFO,N+1).\n\
*\n\n\
* Further Details\n\
* ===============\n\
*\n\
* Based on contributions by\n\
* Jeff Rutter, Computer Science Division, University of California\n\
* at Berkeley, USA\n\
* Modified by Francoise Tisseur, University of Tennessee.\n\
*\n\
* Modified description of INFO. Sven, 16 Feb 05.\n\
* =====================================================================\n\
*\n"
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