giant/CLAUDE.md

# CLAUDE.md

This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.

## Commands

```bash
uv sync --extra cpu                # install dependencies with CPU-only torch (standard/default)
uv sync --extra cuda               # install dependencies with CUDA 11.8 torch
uv sync --extra cpu --extra dev    # add dev extras (pytest, etc.)
uv sync --extra cpu --extra geometry  # add scikit-learn for the geometry oracle (giant rollout)
pytest               # run tests
giant train path/to/steps.parquet --mode flow   # train (flow matching)
giant train path/to/steps.parquet --mode ddpm   # train (DDPM baseline)
giant predict path/to/steps.parquet --checkpoint ckpt/best.pt   # per-step predictions
giant rollout path/to/steps.parquet --checkpoint ckpt/best.pt --geometry oracle.pkl  # full showers
giant analyze submit --rollout roll.parquet --reference test.parquet --out-dir run/ \
  --accounting-group cms                          # parallel rollout-vs-reference analysis on HTCondor
giant analyze render --reduced-dir run/reduced --out run/plots --gallery  # render PDFs + HTML gallery
dwarf --help                                     # dataset/tooling CLI: convert, migrate, bump-gen,
                                                  # bump-schema, status, update-manifest, create-manifest,
                                                  # make-root, build-geometry-oracle, hparam-scan
                                                  # (see scripts/dwarf.py)
```

`cpu` and `cuda` are mutually exclusive — pick one to select the torch build (pinned to 2.3.x; newer torch requires newer NVIDIA drivers). Plain `uv sync` with no extra will not install torch at all; uv has no concept of a "default extra", so `--extra cpu` should always be included unless you need GPU support.

### Lint and type checking

```bash
uv run ruff check .     # lint
uv run ruff format .    # format
uv run ty check .       # type check
```

Part of the `dev` extra. Run these periodically (not just at commit time) to catch drift early.

## Architecture

GIANT is a conditional generative surrogate for the Geant4 step function. It replaces the stochastic physics engine: given a pre-step particle state (conditioning), it samples a post-step outcome — now including the variable-length list of secondary particles the step produces (Phase 2, see Roadmap).

**Data pipeline** (`giant/data/`): parquet files from miniCaloSim are loaded into numpy arrays (`loader.py`), then log-transformed and rotated into a local coordinate frame where `pre_dir = ẑ` (`transforms.py`), before being wrapped in a PyTorch `Dataset` (`dataset.py`). Train/val split is by `event_id` to avoid leaking correlated steps from the same shower.

**Stage-1 output space (9D, `giant/constants.py:LOCAL_TARGET_NAMES`):** `log_step_length`, two additive-log-ratio (ALR) coordinates `edep_logit`/`sec_logit` of a **deposit / secondary / post-energy simplex**, `post_dir` (post-scattering momentum direction, unit vector in the local frame), and `travel_dir` (direction of `post_pos - pre_pos`, unit vector in the local frame). The energy simplex decodes via softmax over `[edep_logit, sec_logit, 0]` × `pre_E` so `edep + e_sec + post_E == pre_E` holds by construction — energy conservation is architectural, not learned (see `energy_simplex_decode`). `post_pos` is not a raw target — it's reconstructed at inference as `pre_pos + step_length * world_frame(travel_dir)`, since `step_length` already encodes that displacement's magnitude and duplicating it would let the two become inconsistent.

**Conditioning vector (15D continuous, `COND_DIM`):** pre-step position, log(pre-energy), pre-step direction, layer ID (`COND_DIM_BASE=8`) — plus, since particle/material physical-property conditioning (`model.conditioning`, see below), 7 more columns: particle `log(mass)`/`charge` (`PARTICLE_PHYS_DIM=2`, `giant/particles.py`) and material `Z_eff`/`A_eff`/`log(density)`/`log(X0)`/`log(λ_int)` (`MATERIAL_PHYS_DIM=5`, `giant/materials.py`). `n_sec` and `e_sec` are **not conditioning inputs** (that was Phase 1 / the energy-conservation PoC); the model predicts them.

`ConditionEncoder`/`SecondaryConditionEncoder` (`giant/model/network.py`) support two mutually exclusive `conditioning` modes, selected per-checkpoint (`model_config["conditioning"]`, defaulting to `"embedding"` for old checkpoints without the key, `"physical"` for new `giant train` runs — see `--conditioning`):
- **`"embedding"`** (original Phase 2 design): a learned `nn.Embedding` per PDG code / material name, indexed by a dataset-scoped dense vocab (`pdg_map`/`mat_map`). Memorizes the training menu.
- **`"physical"`** (default): the 7 physical-property columns above are each routed through a small MLP (`particle_mlp`/`material_mlp`) to the same `emb_dim` width the embedding tables would have produced — a drop-in replacement computable for any PDG code / material name, not just ones seen in training, which is what lets the surrogate generalize to a held-out material or species. `giant/particles.py` decodes nuclear/ion PDG codes (the `10LZZZAAAI` scheme) via the scikit-HEP `particle` package with a Z/A-digit-decode fallback for isomer codes the package's ground-state-only table misses. `giant/materials.py` ships real Geant4-11.4.1-derived `z_eff`/`a_eff`/`density`/`x0`/`lambda_int` values for every material the detector geometry actually produces; the sole exception is `G4_LYSO` (not a stock Geant4 NIST material, never actually constructed by the geometry — see the module docstring), which stays `MaterialProperties(None, ...)` and raises loudly (`MaterialPropertiesNotFilledError`) rather than silently defaulting if it's ever requested.

**Model** (`giant/model/network.py`): a two-stage model, both checkpointed together.
- **Stage 1 — `DenoisingMLP`:** `ResBlock` stack with a `SinusoidalEmbedding` for the flow/diffusion time variable and a `ConditionEncoder` fusing the conditioning. Predicts the 9D primary vector field, plus an `n_sec_head` classifier over `{0..K_MAX}` (`K_MAX=15`) that runs on the condition encoding alone (no diffusion noise), callable via `predict_n_sec`.
- **Stage 2 — `SecondaryDecoder`:** a second flow-matching net (`SecondaryConditionEncoder` fuses the pre-step conditioning with the Stage-1 outcome) that generates all `K_MAX` secondary slots at once. Each slot is `(stick-breaking energy logit, local-frame direction 3D, log-mass, charge)` = `SEC_SLOT_DIM=6`, ordered by descending energy; slots beyond the predicted `n_sec` are masked. Secondary energies are a **stick-breaking partition of the `e_sec` budget** from Stage 1 (they sum to it), so the whole chain conserves energy. A secondary's mass/charge are regressed directly against a fixed physics-derived target (its ground-truth PDG code's `giant.particles.particle_mass_charge`) — not a learned/moving embedding target, so nothing needs detaching. **No snapping at inference**: the predicted (mass, charge) are used as-is as the secondary's physical identity, including for its own future conditioning if it goes on to take further steps in a rollout. A separate, reporting-only nearest-known-PDG lookup (`giant.particles.nearest_known_pdg`) is used purely to populate a nominal `pdg` label for output rows / `"embedding"`-mode fallback conditioning — it never feeds back into the model.

`schedule.py` provides both a `CosineSchedule` for DDPM and the flow matching loss utilities (Lipman et al. 2022 conditional flow matching).

**Samplers** (`giant/sample.py`): DDPM, DDIM, and flow matching (ODE integration, ~10 steps). Flow matching is the primary mode.

**Validation** (`giant/validate.py`): step-level marginal comparisons.

**Analysis** (`giant/analysis/`, `giant analyze` CLI): a lean, streaming rollout-vs-reference plotting pipeline that compares one autoregressive `giant rollout` (for a given checkpoint) against a held-out miniCaloSim reference steps file, and produces publication-styled PDFs assembled into an HTML gallery. It exploits the fact that rollout output and a raw reference file share a world-frame physical column subset under identical names (`pre_*`/`post_*`/`edep`/`step_length`/`pdg`/`material`/`event_id`), so no ALR/local-frame decode is needed — everything is world-frame mm/MeV. Structure: `sources.py` (canonical LazyFrames + synthetic-termination-row filtering + the secondary view, which is `generation>0 & step_no==0` rollout tracks vs exploded `sec_*_list` reference columns), `reduce.py` (the streaming primitives — a single `hist1d` `group_by([group,bin]).len()` pass, per-event scalars, edep-weighted depth/transverse profiles, species share, leakage), `grouping.py`/`context.py` (fixed bin edges + energy-quantile/pdg/material group sets resolved once by `prep` into `shared.json`, so every compute job is one pass with no range scan), `catalog.py` (the declarative `PlotSpec` registry — marginals × {overall,energy,pdg,material}, per-event totals, shower profiles, species/leakage, secondaries), and `render.py` (the only module importing ETPlot's `plotstyle`/LaTeX; dispatches on `Reduced.kind`, writes PDFs + `metadata.yaml`). **Compute/render split:** `giant analyze submit` runs `prep` then submits one HTCondor job per plot (`compute-one`, polars/numpy only — no LaTeX on workers), each writing a small `reduced/<id>.json`; the local `giant analyze render` turns those into the styled PDF/gallery tree. See `giant/analysis/__init__.py`.

**Shower rollout** (`giant/rollout.py`, `giant rollout` CLI): autoregressively steps the two-stage model into a full shower — each primary post-step becomes the next pre-step, secondaries are pushed as new tracks, and per-step `material`/`layer_id` come from a `GeometryOracle` (`giant/geometry.py`, built via `dwarf build-geometry-oracle`) that learns position → (material, layer_id) from data and flags detector escape by nearest-neighbour distance. Tracks terminate on energy cutoff, per-track max steps, escape, or natural end; energy is deposited locally on every stop except escape (leakage), so showers conserve energy by construction.

## Roadmap

**Phase 1 (done):** number of secondaries and their total energy were conditioning inputs; the model predicted only the 9D primary post-step (energy-conservation PoC).

**Phase 2 (implemented — baseline):** the two-stage model above jointly predicts `n_sec`, the energy simplex (`e_sec` falls out of it), and each secondary's energy/direction/species, so a rollout is self-contained (no ground-truth secondary counts injected). This is the "get a baseline out" track agreed with Jan & Tobias (2026-07-07).

**Physical-property conditioning (implemented):** `model.conditioning = "physical" | "embedding"` (see above) replaces the learned PDG/material embeddings with a small MLP over particle mass/charge and material Z_eff/A_eff/density/X0/λ_int, and Stage 2 predicts a secondary's mass/charge directly instead of a snapped species embedding. `"embedding"` stays available as the generalization-comparison baseline. `giant/materials.py`'s table is already filled with real values for every material the geometry produces. **Not yet done:** the actual held-out-material/species generalization comparison against the `"embedding"` baseline is unrun — the 34GB multi-material dataset at the repo root (6 materials, 237 PDG codes including nuclear/ion codes) is the natural dataset for that experiment.

**Next directions** (parallel, not yet built): faster-eval architectures measured against a ~10× native-Geant4 budget — a Wasserstein-GAN throwaway (single-pass eval) and a mixture-of-experts / routing tree of small nets selected per call (pdg / energy / process), with soft/differentiable gating on continuous routing axes; a sampling-calorimeter (multi-material) dataset. See the knowledge base (`/home/lars/knowledge-base/meta/roadmap.md`).