maretopic

maretopic is the official implementation of MARETopic (Manifold-Aware and Rank-based Exemplars Topic Modeling), a training-free topic model that casts topic discovery as rank-based prototype selection.

📢 Accepted at EMNLP 2026 (Main Conference). If you use this package, please see the citation below.

🔍 Overview

Neural topic models produce topics as latent vectors or distributions over the vocabulary — objects with no grounding in any specific text. Clustering-based pipelines pick representative documents only afterwards, by ranking cluster members against a centroid.

MARETopic makes the document the topic. A greedy algorithm selects exactly K leader documents whose neighborhoods cover the corpus, and each leader is the topic: a real text you can open and read.

The selection never uses absolute distances. Documents are encoded, projected onto a low-dimensional manifold, and turned into ranked lists — ordinal neighborhood structure, which is far less affected by the hubness and anisotropy of high-dimensional embedding spaces.

Key properties:

• Training-free: no gradient updates, no variational inference.
• Exactly K topics: the number of topics is an input, not an outcome of density parameters.
• Interpretable by construction: every topic is a corpus document.
• Out-of-sample inference: unseen documents are scored against the leaders without refitting.

📦 Installation

pip install maretopic

To also run the TopMost integration and the example:

pip install "maretopic[topmost]"

The latest development version can be installed directly from source:

pip install "maretopic[topmost] @ git+https://github.com/thcastilho/maretopic"

Dependencies: numpy, scikit-learn, tqdm, sentence-transformers, umap-learn, and interpretable-embeddings (which provides the canonical GRaCE and RaDE implementations).

Requires Python ≥ 3.9.

🧠 Variants

Both variants share the same greedy criterion: pick the candidate that maximizes a score while penalizing redundancy with the leaders already chosen. They differ in how those two quantities are computed, and neither is a reduced form of the other.

MARETopic_Corr — scoring="correlation"

Candidates are scored by a query performance predictor (Reciprocal Density: how strongly a document's neighbors agree on neighborhood membership) and penalized by a rank correlation measure (JaccardMax: maximum Jaccard overlap across prefix depths). Either measure can be swapped without touching the rest of the pipeline.

MARETopic_Diff — scoring="diffusion"

A rank-weighted affinity matrix W is raised to a power, A = W². Its diagonal scores the candidate and its off-diagonal entries penalize redundancy, so the variant needs neither a QPP nor a correlation measure — and runs faster.

🛠 Usage

from maretopic import MARETopic

model = MARETopic(
    num_topics=50,        # K
    top_K=100,            # ranked-list depth
    umap_dim=5,           # 0 disables the UMAP projection
    mmr_diversity=0.3,    # inter-topic MMR weight for keyword extraction
    scoring="correlation" # or "diffusion"
)

model.fit(train_texts)

for words in model.get_top_words():
    print(words)

Each topic is anchored on a real document, and get_leaders() returns their indices in the training corpus:

for topic_id, leader in enumerate(model.get_leaders()):
    print(f"topic {topic_id} is the document: {train_texts[leader][:120]}...")

Unseen documents are projected with the fitted reducer and scored against the leaders — no refitting:

theta = model.transform(test_texts)   # (n_documents, num_topics)
assignments = theta.argmax(axis=1)

Reproducibility

UMAP runs without a fixed random_state, so results vary slightly between fits — the same behavior as BERTopic. Report the mean and standard deviation over several runs, as the paper does. Passing umap_random_state fixes the seed at the cost of UMAP's parallelism.

🔗 TopMost integration

maretopic.topmost.MARETopicTrainer implements the same trainer interface as TopMost's own BERTopicTrainer and FASTopicTrainer, so MARETopic drops into a TopMost evaluation pipeline. Nothing in your topmost installation needs to be patched.

from topmost import BasicDataset, download_dataset
from topmost.eva import clustering, topic_coherence, topic_diversity
from maretopic.topmost import MARETopicTrainer

download_dataset("20NG", cache_path="./data")
dataset = BasicDataset("./data/20NG", read_labels=True, as_tensor=True)

trainer = MARETopicTrainer(dataset, num_topics=50, num_top_words=15)
top_words, train_theta = trainer.train()
train_theta, test_theta = trainer.export_theta()

A complete, runnable version — both variants, all four metrics — is in examples/evaluate_20ng.py.

📁 Package Structure

maretopic/
│
├── model.py         # MARETopic class: fit, transform, get_top_words, get_leaders
├── embeddings.py    # SBERT encoding + ranked-list construction (BallTree)
├── words.py         # c-TF-IDF + inter-topic MMR keyword extraction
└── topmost.py       # MARETopicTrainer adapter for the TopMost toolkit

Leader selection and the training document–topic matrix are delegated to interpretable-embeddings (GRaCE for the correlation variant, RaDE for the diffusion variant), so the algorithms have a single canonical implementation.

📚 Citation

If you use this package in your research, please cite:

Almeida, T. C. C., Pedronette, D. C. G. A Manifold-Aware Topic Modeling Approach via Rank-Based Prototypes Accepted at the 2026 Conference on Empirical Methods in Natural Language Processing (EMNLP), Main Conference.

@inproceedings{almeida2026maretopic,
  title     = {A Manifold-Aware Topic Modeling Approach via Rank-Based Prototypes},
  author    = {Almeida, Thiago C. C. and Pedronette, Daniel C. G.},
  booktitle = {Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing (EMNLP)},
  year      = {2026},
  publisher = {Association for Computational Linguistics}
}

MARETopic builds directly on two earlier methods from the same line of work:

Almeida, T. C. C., Letício, G. R., Valem, L. P., Freitas, A., Pedronette, D. C. G. Effective Graph and Rank-based Contextual Embeddings for Textual and Multimedia Data 2025 International Joint Conference on Neural Networks (IJCNN), Rome – Italy.

De Fernando, F. A., Pedronette, D. C. G., De Sousa, G. J., Valem, L. P., Guilherme, I. R. RaDE+: A semantic rank-based graph embedding algorithm International Journal of Information Management Data Insights, 2(2), 100078, 2022.

🤝 Contact

• Thiago César Castilho Almeida: tc.almeida@unesp.br
• Daniel Carlos Guimarães Pedronette: daniel.pedronette@unesp.br