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.
TRIRED, A, D, E [, /DOUBLE]
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.
An n-element output vector containing the diagonal elements of the tridiagonal array.
An n-element output vector containing the off-diagonal elements.
Set this keyword to force the computation to be done in double-precision arithmetic.
See the description of TRIQL for an example using this function.
EIGENVEC, ELMHES, HQR, LA_TRIRED, TRIQL