-
Notifications
You must be signed in to change notification settings - Fork 104
/
eigvalsym.3
55 lines (55 loc) · 1.61 KB
/
eigvalsym.3
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
.\" Automatically generated by Pandoc 3.1.3
.\"
.\" Define V font for inline verbatim, using C font in formats
.\" that render this, and otherwise B font.
.ie "\f[CB]x\f[]"x" \{\
. ftr V B
. ftr VI BI
. ftr VB B
. ftr VBI BI
.\}
.el \{\
. ftr V CR
. ftr VI CI
. ftr VB CB
. ftr VBI CBI
.\}
.TH "eigvalsym" "1" "2021-02-15" "Fortran 95" "SHTOOLS 4.11"
.hy
.SH EigValSym
.PP
Compute the eigenvalues of a real symmetric matrix.
.SH Usage
.PP
call EigValSym (\f[V]ain\f[R], \f[V]n\f[R], \f[V]eval\f[R],
\f[V]ul\f[R])
.SH Parameters
.TP
\f[V]ain\f[R] : input, real(dp), dimension (\f[V]n\f[R], \f[V]n\f[R])
The input real symmetric matrix.
By default, only the upper portion of the matrix is used.
.TP
\f[V]n\f[R] : input, integer(int32)
The rank of the matrix \f[V]ain\f[R].
.TP
\f[V]eval\f[R] : output, real(dp), dimension (\f[V]n\f[R])
The eigenvalues of \f[V]ain\f[R], sorted from largest to smallest.
.TP
\f[V]ul\f[R] : optional, input, character, default = \f[V]U\f[R]
If \f[V]U\f[R] then the upper portion of the matrix \f[V]ain\f[R] will
be used (default).
If \f[V]L\f[R] then the lower portion of the matrix \f[V]ain\f[R] will
be used.
.SH Description
.PP
\f[V]EigValSym\f[R] will calculate the eigenvalues of a real symmetric
matrix.
By default, only the upper portion of the matrix is used, but this can
be changed by the optional argument \f[V]ul\f[R].
The eigenvalues are sorted from largest to smallest.
The matrix \f[V]ain\f[R] is first factorized into a tridiagonal matrix
using the LAPACK routine \f[V]DSYTRD\f[R], and then the eigenvalues are
calculated by a call to \f[V]DSTEGR\f[R].
.SH See also
.PP
eigvalvecsym, eigvalvecsymtri