---
license: mit
pretty_name: exp190 Phase-Balanced Deep Soft Targets
tags:
  - chess
  - stockfish
  - multipv
  - soft-labels
  - imitation-learning
size_categories:
  - 100K<n<1M
---

# exp190 — Phase-balanced deep MultiPV soft targets

Stockfish **18** MultiPV soft-policy labels with **phase quotas** so training
does not drown in openings. Built for policy-only (no-MCTS) ChessTransformer
finetunes such as [`avewright/chess-transformer-200m-maxelo`](https://huggingface.co/avewright/chess-transformer-200m-maxelo).

## Motivation

Naive HF streaming + shallow MultiPV skews toward openings. Elo without search is
decided in middlegame/endgame. This harvest enforces:

| Phase | Target share | Label depth |
|-------|--------------|-------------|
| Opening | 22% | 10–14 |
| Middlegame | 48% | 12–16 |
| Endgame | 30% | 14–18 |

## Contents

| Path | Description |
|------|-------------|
| `soft_cache.pt` | Torch cache ready for exp189-style training |
| `data/*.jsonl` | Raw labeled positions (FEN + MultiPV soft targets) |
| `status.json` | Harvest counters at upload time |
| `ARCHITECTURE.md` | Design notes for stratified training |

### `soft_cache.pt` tensors

`board_array`, `turn`, `castling`, `ep_square`, `move_idx`, `cp`, `mate`,
`soft_indices`, `soft_probs`, **`phase`**, **`label_depth`**.

Phase encoding: `0=opening`, `1=middlegame`, `2=endgame`.

## How it was generated

- Engine: Stockfish 18 (`x86-64-vnni512`), full strength, MultiPV 8
- FEN sources: HF position streams, book playouts, endgame templates, random walks
- Deficit-first producer + hard phase gate at writer
- Syzygy tablebases when available
- Code: `experiments/exp190_phase_deep_harvest.py` in [avewright/transform](https://github.com/avewright/transform)

## Recommended training use

1. Mix with shallow volume (`exp186-sf-multipv-2m`) at ~30–40% deep / 60–70% shallow
2. Stratify batches by `phase` (1/3 each) so gradients never bog on openings
3. Optional depth weight: `w = label_depth / mean_depth` (clip 0.5–1.5)

## Related

- Shallow soft: [`avewright/exp186-sf-multipv-2m`](https://huggingface.co/datasets/avewright/exp186-sf-multipv-2m)
- Model trained with this mix: [`avewright/chess-transformer-200m-maxelo`](https://huggingface.co/avewright/chess-transformer-200m-maxelo)
- Progress write-up: `docs/PROGRESS_2026-07-10.md` in the transform repo