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giant/CLAUDE.md
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lars 8cebc4809d Apply ruff format and document lint/type tooling in CLAUDE.md
First repo-wide ruff format pass, plus a note in CLAUDE.md to run
ruff and ty periodically.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
2026-06-18 17:40:27 +02:00

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# 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.)
pytest # run tests
python scripts/train.py --data path/to/steps.parquet --mode flow # train (flow matching)
python scripts/train.py --data path/to/steps.parquet --mode ddpm # train (DDPM baseline)
```
`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.
**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.
**Output space (9D):** `step_length` (log), `ΔE` (log), `edep` (log), `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). `post_pos` itself 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:** PDG code (embedding), pre-step position, log(pre-energy), pre-step direction, material (embedding), layer ID, number of secondaries (Phase 1 only — see Roadmap below).
**Model** (`giant/model/`): `DenoisingMLP` built from `ResBlock`s, with a `SinusoidalEmbedding` for the diffusion/flow time variable and a `ConditionEncoder` that fuses all conditioning inputs. `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; shower-level rollout validation is planned.
## Roadmap
Phase 1 (current): number of secondaries is a conditioning input — model predicts only 9D post-step kinematics (including derived post_pos).
Phase 2 (target): model must jointly predict the number of secondaries and all their properties (energy, direction, species), requiring an extended output space and likely a set-based or autoregressive generation scheme for the variable-length secondary list.