- Corrected a bug in congrad.F so the solution to the representer coefficients, cg_x, is loaded into vector ADmodVal at the end of the inner loop, even if the convergence criteria (CGeps) has not been satisfied. That is, the final inner loop solution is loaded if either the algorithm has converged or after Ninner iterations.
- Changed drivers w4dpsas_ocean.h and w4dvar_ocean.h to add an additional argument (Ninner) to the congrad call.
The W4DPSAS algorithm seems to be working well now. It has better convergence behaviour than the W4DVAR algorithm. The stability of the finite amplitude tangent linear model (representer tangent linear model) is affecting the convergence of the W4DVAR algorithm. Some improvement can be achieved by activating the diffusive relaxation in the Picard iterations (RPM_RELAXATION).
The remaining issue in both W4DPSAS and W4DPSAS algorithms is the conjugate gradient preconditioning. The convergence is affected as the number of observation increases.