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Residual Vector.

Let denote a computed eigenvalue, and let
be its corresponding computed eigenvector.
For simplicity, we normalize the computed eigenvector so that
.
The corresponding *residual vector* or
*residual error* is defined by

Ideally, we would like to have , but in practice .
It is conceivable that a small residual error implies
good accuracy in the computed and .
We are interested in knowing how accurate the computed
and are, given .

Susan Blackford
2000-11-20