feat: add store_first_last solver kwarg for memory-light long experiments#5499
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rtimms merged 6 commits intoMay 11, 2026
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…ents When set, the solver only stores the first and last sample of each integration window — one experiment step in `Simulation.solve`, or the full `[t_eval[0], t_eval[-1]]` window in a plain `solve` call. Composes with `output_variables` for ageing simulations whose post-processing only reads per-step first/last values. Has effect on solvers that support intra-solve interpolation (`IDAKLUSolver`); other solvers warn and no-op. With this flag set, intra-step interpolation falls back to linear across the whole step, so it is not appropriate when post-processing queries an intra-step time. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
- Extract `_store_first_last_endpoints` and use it from both `solve()` and `process_t_interp()` so the endpoint array is constructed in one place. - Gate the no-op warning on a per-instance flag so it fires once per non-IDAKLU solver instance instead of once per `step()` call. - Drop a couple of narrating comments restating the next line. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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BradyPlanden
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This is looking good, just a few comments on docs / alignment.
- Drop defensive getattr in BaseStep._setup_timestepping; expose store_first_last on test duck-typed solvers (DummySolver, SolverWithoutInterp) so the attribute is guaranteed on all solver-likes, matching t_eval / t_interp. - Reword store_first_last docstrings in BaseSolver and IDAKLUSolver to drop the ambiguous "Composes with output_variables" phrasing. - Append a section to the 06-output-variables notebook demonstrating store_first_last + output_variables together. - Drop the explanatory comment block above _store_first_last_endpoints in BaseSolver.solve. - Trim docstring on _build_simple_dae_model. - Tighten end-of-step reference-solve tolerance to solver precision (both runs stop at the same t_eval points). Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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BradyPlanden
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Nice one! The notebook results are great 🚀
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Summary
store_first_last: bool = Falsekwarg toBaseSolver(forwarded throughIDAKLUSolver,CasadiSolver,ScipySolver,JaxSolver).True, only the first and last sample of each integration window are stored: one experiment step inSimulation.solve, or the full[t_eval[0], t_eval[-1]]window in plainBaseSolver.solve.output_variablesfor memory-light long ageing experiments whose post-processing only reads per-step first/last values (e.g. metrics built on per-cycle/per-stepFirst/Lastaggregators).IDAKLUSolver); other solvers warn once per instance and no-op.The flag is intended for the case where post-processing only needs first/last state. With this flag set, intra-step interpolation falls back to linear across the whole step (IDAKLU's Hermite checkpoints are auto-disabled by the existing
t_interpnon-empty path), so it is not appropriate when post-processing queries an intra-step time (e.g. aRelativeTime-style sample).Implementation notes
BaseSolver._store_first_last_endpoints, called from bothsolve()(collapsest_evalso IDAKLU stops only at endpoints) andprocess_t_interp()(setst_interpto the same endpoints).BaseStep._setup_timesteppingshort-circuits tot_interp = [0, tf]when the flag is set, overriding any per-stepperiodand any caller-providedt_interp.Serialise.serialise_solverautomatically (reflected from the__init__signature).Test plan
solver.solve(model, t_eval=...)returns 2 stored samples on IDAKLU.periodand callert_interpare overridden when the flag is on.output_variablescomposes (variables-only × endpoints-only).to_config()/from_config()round-trips for IDAKLU and Casadi.🤖 Generated with Claude Code