fix: superposition converges instead of hanging when tlast < tau with auc.type "AUClast" - #588
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fix: superposition converges instead of hanging when tlast < tau with auc.type "AUClast"#588billdenney wants to merge 1 commit into
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… auc.type AUClast With auc.type="AUClast" (or "AUCall"), concentrations after tlast extrapolate as exactly zero, so when tlast < tau the superposed profile keeps structural zeros (for example at time 0 and tau) at steady-state. The zero-concentration guard in the steady-state loop reset the convergence tolerance whenever any concentration was zero, on the assumption that all values eventually become nonzero, so superposition() with the default n.tau=Inf looped forever (issue 580). Two of the twelve Theoph subjects have tlast < 24, so a superposition(conc_obj, tau=24, auc.type="AUClast") call on that dataset hung. Now, once a completed dosing interval draws all of its concentrations from times after tlast, any remaining zero concentration can never become nonzero, so steady-state is assessed on the nonzero concentrations only, and a warning explains that zero concentrations remain in the steady-state profile. Zeros that can still accumulate from later dosing intervals keep the previous guard behavior, so all previously-converging cases are unchanged (verified byte-identical before and after the fix for AUCinf steady-state on all Theoph subjects, finite-n.tau AUClast, and the documented multi-dose cases). A generous 10000-interval backstop now raises an informative error instead of looping forever if steady-state cannot be reached. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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Fixes #580.
The steady-state loop's zeros guard reset the convergence tolerance every iteration, so structural zeros from
auc.type = "AUClast"/"AUCall"tail handling (when a subject's tlast < tau) maden.tau = Infloop forever. The tolerance logic now distinguishes zeros that can still accumulate (previous behavior kept) from zeros originating after tlast, which can never become nonzero — those converge on the nonzero concentrations with a warning naming the persisting zeros, tlast, and auc.type. A generous 10,000-interval cap errors informatively as a backstop.Verification: nine reference results (AUCinf steady state, finite n.tau, dose-scaled, multi-subject) are byte-identical before/after, verified by stash-toggling the source; the formerly-hanging Theoph case now returns in ~0.05 s with the expected warning; the cap error path is exercised in tests. Full superposition + TSS test files pass.
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