torchPersLay

torchPersLay is a native PyTorch implementation of PersLay, a neural-network layer for persistence diagrams in topological data analysis. The package is published on PyPI as torchPersLay; the Python import package is perslay.

This repository focuses on PersLay-style persistence-image features with learnable point weights and Gaussian bandwidths. Earlier DeepSet experiment code has been removed to keep the package focused on the successful PersLay implementation.

Installation

Install the released package from PyPI:

pip install torchperslay

Install the local repository in editable mode:

git clone https://github.com/jhnrckmnznrs/torchPersLay.git
cd torchPersLay
pip install -e .

To run the experiment scripts in this repository, also install the experiment extra or the repository requirements:

pip install -e ".[experiments]"
# or
pip install -r requirements.txt

Quick start

The example below builds a PersLay regressor for a small batch of padded persistence diagrams. Diagrams are expected as (birth, death) pairs with shape [batch, num_points, 2].

import torch

from perslay import (
    GaussianPerslayPhi,
    NormalizedLearnablePowerPerslayWeight,
    Perslay,
)
from perslay.models import FlattenRho

image_size = [10, 10]
image_bnds = [[0.0, 1.0], [0.0, 1.0]]  # birth bounds, persistence bounds

weight = NormalizedLearnablePowerPerslayWeight(image_bnds=image_bnds)
phi = GaussianPerslayPhi(
    image_size=image_size,
    image_bnds=image_bnds,
    sigma_x=0.1,
    sigma_y=0.1,
    normalize=False,
)

perslay = Perslay(
    weight=weight,
    phi=phi,
    perm_op=torch.sum,
    rho=FlattenRho(),
)

# Two padded diagrams with three points each.
diagrams = torch.tensor(
    [
        [[0.0, 0.4], [0.2, 0.8], [0.0, 0.0]],
        [[0.1, 0.5], [0.3, 0.9], [0.4, 0.95]],
    ],
    dtype=torch.float32,
)
mask = torch.tensor(
    [
        [True, True, False],
        [True, True, True],
    ]
)

features = perslay(diagrams, mask=mask)
print(features.shape)  # torch.Size([2, 100])

Regression models

For most regression experiments, use the provided model wrappers:

from perslay.models import PerslayRegressor, MultiPerslayRegressor

model = PerslayRegressor(
    image_size=[20, 20],
    image_bnds=[[0.0, 1.0], [0.0, 1.0]],
    sigma_x=0.05,
    sigma_y=0.05,
    hidden_dim=128,
    weight_type="normalized_learnable_power",
)

Available weight_type values are:

• constant
• learnable_power
• normalized_learnable_power
• mlp

MultiPerslayRegressor supports multiple homology dimensions or multiple diagram sources per sample. See experiments/configs/h0_h2_regression.yaml for an example configuration.

Repository layout

src/perslay/
  data.py      Dataset and collate utilities for persistence-diagram CSV files
  layers.py    PersLay layers, feature maps, and point-weight functions
  models.py    Single-branch and multi-branch PersLay regressors

experiments/
  train_regression.py       Config-driven regression training script
  configs/degree2_regression.yaml
  configs/h0_h2_regression.yaml

Running experiments

Prepare persistence diagram CSV files with columns similar to:

birth,death
0.1,0.4
0.2,0.8

Prepare a target CSV with:

filename,target
sample_001.csv,3.14

Then run:

python experiments/train_regression.py --config experiments/configs/degree2_regression.yaml

For multi-diagram input, use:

python experiments/train_regression.py --config experiments/configs/h0_h2_regression.yaml

Training writes checkpoints and resolved configs under the configured output.run_dir.

Citation

If you use this package in research, please cite the original PersLay paper:

Mathieu Carrière, Frédéric Chazal, Yuichi Ike, Théo Lacombe, Martin Royer, and Yuhei Umeda. PersLay: A Neural Network Layer for Persistence Diagrams and New Graph Topological Signatures. AISTATS 2020, PMLR 108:2786–2796.

License

This project is distributed under the MIT License. See LICENSE for details.