
Up: Efficient implementations of
- 1.-3.
- These steps are similar to Algorithm 2.3 (click here),
except that
is kept in
factored form.
- 4.
- For each of the q columns of
, apply
steps of
the LSQR algorithm to produce the solutions

- 5.
- Compute the estimates of f and the corresponding variances
at

- 6.
- If needed, compute the corresponding averaging kernels

Changing the target functions requires re-computing steps 4 through
6. In this variant of the algorithm the k acts as the regularization
parameter; increasing k requires additional steps of the LSQR
algorithm to be computed in step 4. If k is decreased no extra
Lanczos iterates are needed, provided the iteration vectors
are saved. In any case steps 5 through 6 need to be
re-computed.
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