Summary
OpenCMP currently rejects restarting history-dependent multistep schemes because a restart loads only one checkpoint, while schemes such as CNLF, SBDF, and adaptive IMEX require multiple consecutive previous solutions.
Saved .sol files cannot reliably provide this history because save_frequency may skip time steps.
Proposed solution
After loading the restart checkpoint, use a single-step method such as implicit Euler to generate the missing solution history. Once enough accepted warm-up steps have been completed, switch back to the configured multistep scheme.
The warm-up should use an appropriate time step, respect the simulation end time, and correctly populate the solution and time-step histories. IMEX schemes may need Euler IMEX as their warm-up method.
Acceptance criteria
- Restart works for CNLF, SBDF, and adaptive IMEX from one checkpoint.
- The solver switches to the configured multistep scheme after warm-up.
- Existing single-step restart behavior remains unchanged.
- Tests and restart documentation cover the new behavior.
Summary
OpenCMP currently rejects restarting history-dependent multistep schemes because a restart loads only one checkpoint, while schemes such as CNLF, SBDF, and adaptive IMEX require multiple consecutive previous solutions.
Saved
.solfiles cannot reliably provide this history becausesave_frequencymay skip time steps.Proposed solution
After loading the restart checkpoint, use a single-step method such as implicit Euler to generate the missing solution history. Once enough accepted warm-up steps have been completed, switch back to the configured multistep scheme.
The warm-up should use an appropriate time step, respect the simulation end time, and correctly populate the solution and time-step histories. IMEX schemes may need Euler IMEX as their warm-up method.
Acceptance criteria