The TRIRED procedure uses Householder’s method to reduce a real, symmetric array to tridiagonal form.
TRIRED is based on the routine tred2 described in section 11.2 of Numerical Recipes in C: The Art of Scientific Computing (Second Edition), published by Cambridge University Press, and is used by permission.
Note: If you are working with complex inputs, use the LA_TRIRED procedure instead.
Examples
See the description of TRIQLfor an example using this function.
Syntax
TRIRED, A, D, E [, /DOUBLE]
Arguments
A
An n by n real, symmetric array that is replaced, on exit, by the orthogonal array Q effecting the transformation. The routine TRIQL can use this result to find the eigenvectors of the array A.
D
An n-element output vector containing the diagonal elements of the tridiagonal array.
E
An n-element output vector containing the off-diagonal elements.
Keywords
DOUBLE
Set this keyword to force the computation to be done in double-precision arithmetic.
Version History
| 4.0 |
Introduced |
See Also
EIGENVEC, ELMHES, HQR, LA_TRIRED, TRIQL
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