ram-wnn 0.2.1

Weightless Neural Networks for Language Modeling — RAM-based neurons in PyTorch

ram-wnn

Weightless Neural Networks for Language Modeling — RAM-based neurons in PyTorch.

This research explores whether Weightless Neural Networks (WNNs) — specifically RAM-based neurons — can serve as a foundation for language modeling, traditionally dominated by weighted transformer architectures.

RAM neurons use lookup tables instead of weighted connections. Partial connectivity is the generalization mechanism: each neuron observes a subset of input bits, so similar inputs map to the same address and trigger the same response.

Installation

pip install ram-wnn

Requires Python 3.11+ and PyTorch 2.0+.

Quick Start

from wnn.ram.core.models.bitwise_ramlm import BitwiseRAMLM
from wnn.eval import WIKITEXT2_TEST

# Create a per-bit output language model (16 clusters for GPT-2's 16-bit vocab)
model = BitwiseRAMLM(
    vocab_size=50257,      # GPT-2 tokenizer
    context_size=4,        # 4-gram context
    neurons_per_cluster=200,
    bits_per_neuron=20,
)

# Load WikiText-2 test data (GPT-2 BPE tokenizer)
tokens = WIKITEXT2_TEST.load_tokens()

# Train
model.train_on_tokens(tokens[:200_000])

# Evaluate
stats = model.evaluate_fast(tokens[200_000:])
print(f"CE: {stats['cross_entropy']:.2f}, PPL: {stats['perplexity']:.0f}")

Key Results

All models evaluated on WikiText-2 with GPT-2 tokenizer (50,257 vocab).

Architecture	CE	PPL	Acc	Notes
Random baseline	10.82	50,257	0.002%	Uniform prediction
Tiered RAMLM (50K clusters)	~10.20	~27,000	~4.9%	5-tier, EMPTY=0.0
BitwiseRAMLM (16 clusters)	~9.15	~9,400	~6.6%	Per-bit prediction
Target: GPT-2 Small (124M)	3.38	29.41	--	Zero-shot

Architecture

BitwiseRAMLM

Instead of 50K output clusters (one per token), BitwiseRAMLM uses 16 clusters (one per output bit). Each cluster predicts P(bit_i=1 | context). Token probabilities are reconstructed via log-product:

log P(token=t) = Σ_i [b_i(t)·log(P_i) + (1-b_i(t))·log(1-P_i)]

Key advantage: every neuron sees ALL training examples (not just ~20 for rare tokens).

Tiered RAMLM

Frequency-based architecture where frequent tokens get more capacity:

Tier	Tokens	Neurons	Bits	Data %
0	50 most frequent	15	20	42%
1	Next 50	13	18	5%
2	Next 400	9	10	13%
3	Next 20K	7	9	37%
4	Rest (~30K)	5	8	3%

Reproducibility

Save and load checkpoints for reproducible results:

from wnn.eval import Checkpoint, WIKITEXT2_TEST

# Save (connections only = ~381 KB)
Checkpoint.save(
    path="checkpoints/my_model",
    model=model,
    eval_task=WIKITEXT2_TEST,
    results={"ce": 9.15, "ppl": 9430, "accuracy": 0.066},
)

# Load and reconstruct
ckpt = Checkpoint.load("checkpoints/my_model")
model = ckpt.create_model()
print(ckpt.summary())

Rust+Metal Accelerator (Optional)

For Apple Silicon Macs, a Rust accelerator provides 3-8x speedup using Metal GPU compute:

# Requires Rust toolchain
cd src/wnn/ram/strategies/accelerator
pip install maturin
maturin develop --release

# Verify
python -c "import ram_accelerator; print(ram_accelerator.cpu_cores())"

The accelerator is optional — all functionality works with pure PyTorch.

Research Blog

Follow the research progress at lacg.github.io/llm-optimizer.

Citation

@software{garcia2025ramwnn,
  author = {Garcia, Luiz Alberto Crispiniano},
  title = {RAM-WNN: Weightless Neural Networks for Language Modeling},
  year = {2025},
  url = {https://github.com/lacg/wnn}
}

License

MIT