Adds model.conditioning = "physical" | "embedding": physical mode routes
particle mass/charge and material Z_eff/A_eff/density/X0/lambda_int through
small MLPs to replace the learned PDG/material embedding tables, so the
surrogate generalizes to PDG codes/materials outside the training vocab
instead of memorizing it. "embedding" stays available as the comparison
baseline (old checkpoints without the key default to it).
Stage 2 now regresses a secondary's mass/charge directly against a fixed
physics-derived target instead of a learned/snapped embedding, and uses no
snapping at inference — the model's raw predicted (mass, charge) is the
secondary's physical identity, including for its own further rollout steps.
A separate reporting-only nearest-known-PDG lookup (never fed back into the
model) populates output pdg columns / the embedding-mode rollout fallback.
giant/materials.py's table is populated with Geant4's own built-in NIST
constants (Z_eff, A_eff, density, X0, lambda_int), extracted directly from
the Geant4 11.4.1 build vendored in minicalosim via G4NistManager rather
than hand-typed literature values. G4_LYSO is left unfilled: confirmed (both
by runtime lookup and by searching minicalosim's history) that it's never
actually a constructed Geant4 material there, only documentation/UI color-map
text.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
decode_secondaries's stick-breaking only guarantees valid secondary slots
sum to <= e_sec, leaving a shortfall that rollout.py silently dumped into
that step's edep. Rescale the valid slots by one common per-row factor
instead, so they sum to exactly e_sec whenever n_sec > 0: this spreads any
shortfall proportionally across all secondaries rather than concentrating
it in whichever slot is last by energy rank (which would let that one
low-energy secondary balloon and distort the shower's topology). Rows
where every valid slot decodes to ~zero fall back to an even split.
n_sec == 0 rows are unchanged (still nothing to carry the budget, so
rollout.py's edep top-up still applies there) — narrowed the related
caveat in load_rollout_vs_truth's docstring to just that case.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
lars