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Since every bc value is packed into a fresh Function on V (_pack_bc_value), `bc.g` is a snapshot of `g` taken at construction. The standard time-dependent pattern -- build the bc once, then `assign(new_value, g)` before every solve -- therefore silently solved with the construction-time value (typically zero), and the tape also kept depending on `g`'s construction-time block variable, so replay and gradients were wrong too. test_time_dependent_bc_replay did not catch it, since it only compares replay against an equally wrong forward run. DirichletBC now keeps its source expression and a compiled interpolation Expression, and exposes `_ad_refresh(annotate)`, which LinearProblem/ NonlinearProblem call on every bc before each solve: it re-packs the current source value into `bc.g`, and when annotating and the source's block variables changed since the last packing, records a fresh ExprInterpolationBlock + DirichletBCBlock so the solve depends on the bc value at that point of the tape. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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Since every bc value is packed into a fresh Function on V (_pack_bc_value),
bc.gis a snapshot ofgtaken at construction. The standard time-dependent pattern (build the bc once, thenassign(new_value, g)before every solve) therefore silently solved with the construction-time value (typically zero), and the tape also kept depending ong's construction-time block variable, so replay and gradients were wrong too. test_time_dependent_bc_replay did not catch it, since it only compares replay against an equally wrong forward run.DirichletBC now keeps its source expression and a compiled interpolation Expression, and exposes
_ad_refresh(annotate), which LinearProblem/ NonlinearProblem call on every bc before each solve: it re-packs the current source value intobc.g, and when annotating and the source's block variables changed since the last packing, records a fresh ExprInterpolationBlock + DirichletBCBlock so the solve depends on the bc value at that point of the tape.