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ML Reproducibility Challenge 2021

This repository hosts documents and code for reproducing the algorithm for updating the truncated singular value decomposition (SVD) of evolving matrices outlined by Vassilis Kalantzis, Georgios Kollias, Shashanka Ubaru, Athanasios N. Nikolakopoulos, Lior Horesh, and Kenneth L. Clarkson in their paper Projection techniques to update the truncated SVD of evolving matrices published in the 38th International Conference on Machine Learning 2021. We (Andy Chen, Shion Matsumoto, and Rohan Sinha Varma) present this repository as part of a submission to the ML Reproducibility Challenge 2021 along with our report.

Introduction

Problem Statement

In applications where the matrix is subject to the periodic addition of rows (and/or columns), re-calculating the SVD with each update can quickly become prohibitively expensive, particularly if the updates are frequent. For this reason, algorithms that exploit previously available information on the SVD of the matrix before the update to calculate the SVD of the update matrix are crucial. This can be in the context of both the full SVD and the rank-k SVD, the latter of which is the focus of our study.

Algorithms

In our study, we use three algorithms to calculate the truncated SVD of evolving matrices:

  1. Zha-Simon projection-based update algorithm (Algorithm 2.1)
  2. Enhanced projection-based update algorithm (Algorithm 2.2)
  3. FrequentDirections

Though we will not discuss the specifics of each of the algorithms we used, each experiment followed a similar structure. The basic structure is listed below

  1. Evolve matrix by appending rowsaccording to the specified updating scheme
  2. Calculate truncated SVD of updated matrix using desired update method
  3. Calculate metrics for updated truncated SVD

Evaluation

The performance of each algorithm is evaluated using three metrics:

  1. Relative singular value error
  2. Scaled residual norm singular triplet
  3. Runtime

How to Run Experiments

The following sections provide instructions on the installation in order to run the experiments as well as the datasets used in the study.

Conda Environment Setup

The necessary dependencies are listed in the environment.yml file and can be used to set up a new Anaconda environment for running the experiments in this repository.

conda env create -n <env-name> -f environment.yml
conda activate <env-name>

Datasets

The datasets have been converted into a convenient format and can be accessed here. Note that a few of the datasets had to be converted from a sparse into dense format.

Running Experiments

The experimental parameters are specified in a JSON file as follows:

{
  "tests": [
    {
      "dataset": "CRAN",
      "method": ["zha-simon", "bcg", "frequent-directions"],
      "m_percent": 0.1,
      "n_batches": [2, 6, 10],
      "phis_to_plot": [1, 5, 10],
      "k_dims": [25, 50, 75, 100, 125],
      "make_plots": true
    },
    {
      "dataset": "CISI",
      "method": ["zha-simon", "bcg", "frequent-directions"],
      "m_percent": 0.1,
      "n_batches": [2, 6, 10],
      "phis_to_plot": [1, 5, 10],
      "k_dims": [25, 50, 75, 100, 125],
      "make_plots": true
    }
  ],
  "dataset_info": {
    "CISI": "./datasets/CISI.npy",
    "CRAN": "./datasets/CRAN.npy",
    "MED": "./datasets/MED.npy",
    "ML1M": "./datasets/ML1M.npy",
    "Reuters": "./datasets/reuters.npy"
  },
  "method_label": {
    "bcg": "$Z = [U_k, X_{\\lambda,r}; 0, I_s]$",
    "zha-simon": "$Z = [U_k, 0; 0, I_s]$",
    "frequent-directions": "FrequentDirections"
  }
}

Below are tables listing parameters and their descriptions. Please see our JSON files in the experiments directory for complete examples.

Parameter Description Example
tests List of json objects describing tests See table below
dataset_info Name and location of datasets used in tests "CRAN": "./datasets/CRAN.npy"
method_label JSON object containing labels used in plots for each method "zha-simon": "$Z = [U_k, 0; 0, I_s]$"

The tests parameter provides a list of json objects specifying all the tests to be run. Below we detail what these JSON objects must contain. Note if BCG is being run on any dataset, the BCG only parameters must be included

Parameter Description Example
dataset Name of dataset to run on "CRAN"
method List of update methods to run ["zha-simon", "bcg", "frequent-directions"]
m_percent Percent of data used as initial matrix 0.1
n_batches Number of update batches [2, 6, 10]
phis_to_plot Batch numbers to plot [1, 5, 10]
k_dims Rank of updates [25, 50, 75, 100]
make_plots Option to plot update results true
r_values Number of oversamples(BCG only) [10, 20, 30, 40, 50]
lam_coeff Lambda Coefficient (BCG only) 1.01
num_runs Number of runs for BCG experiment (BCG only) 1

To run the experiment, all you have to do is call run_tests.py and specify the path to the JSON file and the directory to contain the cache folder where results and figures will be stored. Additional plots can be created by using make_runtime_plots.py and specifying a JSON file specifying plot parameters and the cache location.

The parameters for the JSON file for the runtime plotting script are listed below. An example can be found in experiments/plot_spec.json

Parameter Description Example
n_batches Set of 'number of update batches' values to generate runtime graphs over, plots will have runtime on y-axis and rank on x-axis [2,6,10]
ranks Set of rank values to generate runtime graphs over, plots will have runtime on y-axis and rank on x-axis [25,50,75,100]
method_label JSON object containing labels used in plots for each method "zha-simon": "$Z = [U_k, 0; 0, I_s]$"
datasets List of strings containing names of datasets to generate plots for ["CISI","CRAN","MED"] 
# Navigate to truncatedSVD root directory
cd [...]/truncatedSVD

# If cache directory not specified, defaults to current directory
python run_tests.py -e <tests.json>

# Option to explicitly set cache directory
python run_tests.py -e <tests.json> -c <cache_directory>

# Make Runtime plots comparing methods for each specified dataset
python make_runtime_plots.py -c <cache_directory> -s <plot_params.json>

Note: Depending on the number of experiments, the cache can become large (~1 GB), so please ensure that your system has sufficient space before running the experiments.

Results

In one of our experiments, we evaluated the Zha-Simon and enhanced projection variations of the proposed algorithm and FrequentDirections on the CRAN dataset with n_batches=10, k_dims=50, and r=10. Shown below are plots of the relative singular value errors and scaled residual norms of the first 50 singular triplets for the first, fifth, and tenth updates using the Zha-Simon projection-based update method (first line), enhanced projection-based update method (second line), and FrequentDirections (third line).

For our complete set of results, please refer to our report and supplementary materials.

Team

Andy Chen, Shion Matsumoto, and Rohan Sinha Varma

Acknowledgments

We would like to acknowledge Professor Laura Balzano for introducing us to this challenge and also for advising us on this project. We would also like to thank Professor Vassilis Kalantzis for providing us with the code used in producing their results.