nomic-embed-text-v1-unsupervised-cs-surgery

Surgically extended version of nomic-ai/nomic-embed-text-v1-unsupervised for academic Computer Science text.

Part 1 deliverable: expanded fast tokenizer + aligned input embeddings. No fine-tuning — new token rows are initialized with FVT (mean of old subword pieces).

Summary

How surgery was done

1. Corpus — streamed ~250k arxiv papers with cs.* categories (title + abstract) + Qasper full text.
2. Token selection — rank whole words by corpus frequency; keep those absent from Nomic vocab, fragmented into ≥2 pieces, freq ≥ 30, lowercase alpha ≥3 chars; drop LaTeX/placeholder artifacts; take top 500.
3. Tokenizer — insert tokens into fast tokenizer source of truth: tokenizer.json → model.vocab (WordPiece). Sync vocab.txt as slow-path mirror only. Not HF add_tokens.
4. Embeddings — build pad-aware W_new; copy rows 0..30521 unchanged; FVT-init new rows; set vocab_size=31040.
5. Verify — round-trip: tokenize(term) → one new id → that id indexes the initialized row; old rows untouched; general-text cosine ≈ 1 vs base.

Added tokens (preview)

First 50 of 500:

dataset, stochastic, datasets, gaussian, clustering, convolutional, embedding, probabilistic, decoding, dynamical, deterministic, bayesian, segmentation, embeddings, markov, achieves, polarization, asymptotic, mimo, experimentally, outperforms, queries, iterative, metrics, benchmark, photonic, throughput, generalization, relativistic, characterize, heterogeneous, robustness, dispersion, localization, excitation, planar, numerically, dipole, classifier, correlations, architectures, decoder, approximations, frac, automata, variational, dielectric, recurrent, latent, optimized

Full list: added_domain_tokens.json

Files

Usage

from transformers import AutoTokenizer, AutoModel
import torch
import torch.nn.functional as F

repo = "OmarH455/nomic-embed-text-v1-unsupervised-cs-surgery"
tok = AutoTokenizer.from_pretrained(repo)
model = AutoModel.from_pretrained(repo, trust_remote_code=True)
model.eval()

# Round-trip check: domain term is one token
assert tok.tokenize("convolutional") == ["convolutional"]
assert tok.encode("bayesian", add_special_tokens=False) == [tok.convert_tokens_to_ids("bayesian")]

def mean_pool(out, mask):
    e = out[0]
    m = mask.unsqueeze(-1).expand(e.size()).float()
    return (e * m).sum(1) / m.sum(1).clamp(min=1e-9)

text = "search_document: Stochastic gradient methods for convolutional segmentation on large datasets."
enc = tok(text, return_tensors="pt")
with torch.no_grad():
    emb = mean_pool(model(**enc), enc["attention_mask"])
    emb = F.normalize(emb, p=2, dim=1)
print(emb.shape)  # [1, 768]

Verification (local)

python surgery/cs_phase4_verify.py

Checks: round-trip for all 500 tokens, pretrained rows unchanged, general-text cosine ≈ 1, domain sentence embeds cleanly.

Important notes

• Default load uses the fast tokenizer; tokenizer.json is the source of truth (not vocab.txt alone).
• Nomic pads embeddings to a multiple of 64 (30522 real vocab → 30528 matrix originally). New size 31040 follows the same rule.
• New embeddings are warm-started only. Domain geometry improves after continued / contrastive training.
• Requires trust_remote_code=True (NomicBert custom code).

References

• HF Course Ch.6 — Tokenizers · WordPiece · Build tokenizer
• Nomic 30522 vs 30528 discussion
• tokenizers#1160
• Base: nomic-embed-text-v1-unsupervised