= MeqSolver =
The general equation solver
Initrec
Field |
Default |
Comment |
num_iter |
3 |
Maximum number of solver iterations |
epsilon |
0.0 |
Fit considered converged if solver "fit" parameter < epsilon, see below. epsilon=10-4 is generally a good value. Set num_iter to a high value, like 20. Usually the fit converges in 3 or fewer iterations. |
last_update |
False |
Update parameters after solve converged. Set this one and save_funklets to True if you want to store the solutions in a ParmTable |
save_funklets |
False |
Set to True if you want to store the solutions in a ParmTable |
use_svd |
True |
Use a Singular Value Decomposition matrix inversion. HIGHLY RECOMMENDED |
Stopping condition
From now on the solver stops iterating when
- iteration == num_iter
- OR
abs(fit) < epsilon AND fit < 0.0
10-4 appears to be a sensible setting for epsilon.
fit < 0.0 implies that chi-squared decreased during the last iteration. One should NEVER stop after iterations that increased chi-squared. Set num_iter to 20 or 40 or something similar to catch difficult cases.
I added two fields to the solver metrics:
- Iterations: number of iterations used in solution
- Converged: indicates whether convergence was achieved.