qwen3-geotikz

Spec-First Geometry → TikZ: LoRA adapters (Qwen3)

LoRA adapters that fine-tune small Qwen3 base models to turn a coordinate-free geometry scene description (relationships only, no explicit coordinates) into a single compiling TikZ/PGF figure whose every named point is numerically correct: recovering the hidden numbers from the geometry rather than transcribing them.

The behavior is graded by one falsifiable gate: figure-only AND compiles under tectonic AND every named coordinate within atol=0.05 of the ground-truth construction.

Thesis: you can make a small model reliably do one narrow thing by controlling its training data, and how you frame the target (compute the answer vs. emit the construction) matters more than model size or dataset size. Full narrative + evidence: DEMO_WRITEUP.md in the source repo.

Adapters in this repo

All adapters are LoRA (all-linear), bf16, trained with TRL + PEFT on a Modal GPU. qwen3-*-geotikz: r=16, α=32, 2 epochs. qwen3-illustrator*: r=32, α=64, 2 epochs.

How to use

Each adapter is a standard PEFT LoRA on the stated base. Inference disables Qwen3's "thinking" block so the output is pure, figure-only TikZ.

import torch
from transformers import AutoModelForCausalLM, AutoTokenizer
from peft import PeftModel

BASE = "Qwen/Qwen3-0.6B"                 # match the adapter's base model
REPO = "kyhe/qwen3-geotikz"              # this Hub repo
ADAPTER = "qwen3-pgf-geotikz"            # subfolder for the v2 specialist

tok = AutoTokenizer.from_pretrained(BASE)
model = AutoModelForCausalLM.from_pretrained(BASE, dtype=torch.bfloat16)
model = PeftModel.from_pretrained(model, REPO, subfolder=ADAPTER).eval()

SYSTEM = (
    "You are a geometry-to-TikZ compiler. Given a geometry scene described only through "
    "relationships and constraints (no explicit coordinates), you must derive the exact "
    "coordinates yourself and output a single valid TikZ/PGF figure that compiles and "
    "renders the described geometry. Output ONLY the TikZ code, starting with "
    "\\begin{tikzpicture} and ending with \\end{tikzpicture}. No prose, no markdown fences."
)
scene = ("There is a circle centered at the origin with radius 3. Point A lies on the "
         "circle at 40 degrees. Point B lies on the circle at 200 degrees. Point M is the "
         "midpoint of segment AB.")
msgs = [{"role": "system", "content": SYSTEM},
        {"role": "user", "content": f"Scene:\n{scene}\n\nReturn the TikZ figure."}]
prompt = tok.apply_chat_template(msgs, tokenize=False, add_generation_prompt=True,
                                 enable_thinking=False)
out = model.generate(**tok(prompt, return_tensors="pt").to(model.device),
                     max_new_tokens=512, do_sample=False)
print(tok.decode(out[0][tok(prompt, return_tensors="pt")["input_ids"].shape[1]:],
                 skip_special_tokens=True))

Compile the emitted \begin{tikzpicture}…\end{tikzpicture} with tectonic (wrap in a standalone doc with tkz-euclide + calc/intersections; see src/geotikz/serve.py).

Evaluation

Objective gate, no human/LLM judge required: figure-only + compile (tectonic) + static-parser coordinate assertion at atol=0.05 (src/geotikz/harness.py). Named-center constructions use a compile-extract grader (src/geotikz/extract.py). Base vs. tuned is scored on the identical held-out grid the frontier models were scored on.

v1 numeric target: pass rate on the 800-item difficulty grid:**

On that same grid, tuned-1.7B (0.598) beats prompted gpt-4.1 (0.555), gpt-4o (0.439), deepseek-v3.2 (0.270), claude-haiku-4-5 (0.173). Top-tier frontier (e.g. claude-sonnet-5 0.977) stays ahead, as expected; the win is reliable + cheap + local + a data-driven jump from 2/800 to 371/800.

v2 construction target (qwen3-pgf-geotikz): 280-item PGF eval:**

Same base model + recipe as v1; only the target representation changed. The hardest construction went 0.02 → 0.98.

qwen3-illustrator: held-out synthetic (240, coordinate-verified) and real AIME (150):**

Intended use & limitations

• Intended: bulk, local, offline illustration of in-distribution coordinate-free geometry scenes (worksheets, figure drafts, the trained construction vocabulary). Guaranteed well-formed, compiling, coordinate-free output.
• Not intended: general-purpose diagramming or "solve/illustrate any competition problem." On arbitrary hard AIME the illustrator reliably draws a figure (69%) but the correct one only ~11%. Coverage is reasoning-bound, not drawing-bound. Use the frontier-fallback routing for the hard tail.
• Scope: planar Euclidean constructions; 3D / heavily combinatorial figures are out of scope for the local model.
• License: adapters released under Apache-2.0, matching the Qwen3 base models.

Training & data

Synthetic data is generated forward from exact coordinates and then the coordinates are stripped for the model input, so labels are correct by construction (no teacher hallucination) and difficulty is exactly controllable. The illustrator additionally distills a frontier teacher (gpt-5.5) with a two-stage compile + vision-judge filter. Dataset: see the companion dataset card. Code: source repo (src/geotikz/, scripts/).