All of the linear solvers in *COOOL*are iterative.
Descriptions of the algorithms can be found in
in the book by Scales and Smith listed at the end.
Presently *COOOL* implements two flavors of
row action methods: **ART**, which stands for
Algebraic Reconstruction
Technique, and **SIRT**, which stands for Simultaneous
Iterative Reconstruction Technique.
These methods are especially attractive when problems are too
big to fit into memory.
When the matrix elements will fit into memory,
Conjugate Gradient Least Squares (**CGLS**) is very attractive.
Finally, we implement a version of the **IRLS**
algorithm (Iteratively Re-weighted Least-Squares)
to efficiently solve linear systems in the norm.
This algorithm takes advantage of certain approximations to
achieve nearly the speed of conventional least squares methods
while being able to robustly handle long-tailed noise distributions.

Sun Feb 25 12:08:00 MST 1996