PCGN: Preconditioned Conjugate Gradient Solver with Improved Nonlinear Control

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The Preconditioned Conjugate Gradient Solver with Improved Nonlinear Control (PCGN) package provides additional controls that can be useful with difficult problems. The pane for this package is on the MODFLOW Packages and Programs dialog box under Solvers.

The PCGN: Preconditioned Conjugate Gradient Solver with Improved Nonlinear Control pane has two tabs: Basic and Non-Linear.

The items on the Basic tab are similar to those for the PCG package.

Maximum number of Picard (outer) iterations (ITER_MO). If the Lake package is used, more iterations may be required.

Maximum number of PCG (inner) iterations (ITER_MI)

The residual-based stopping criterion for iteration (CLOSE_R)

The head-based stopping criterion for iteration (CLOSE_H)

Relaxation parameter (RELAX)

Fill level of the MIC preconditioner (IFILL)

Save progress for the inner PCG iteration to file (UNIT_PC)

Save time in the PCG solver to file (UNIT_TS)

The items on then Non-Linear tab provide additional controls.

Damping mode (ADAMP)

Damping parameter control (DAMP)

Lower limit for DAMP (DAMP_LB)

Rate parameter for adjusting DAMP (RATE_D)

Maximum head change (CHGLIMIT)

Convergence mode (ACNVG)

Minimum value for relative convergence (CNVG_LB)

Power factor for increasing PCG convergence criteria (MCNVG)

Convergence enhancement control (RATE_C)

Progress reporting for the Picard iteration (IPUNIT)