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Multimodal Mixture-of-Experts VAE

This repository contains the code for the framework in Variational Mixture-of-Experts Autoencodersfor Multi-Modal Deep Generative Models (see paper).

Requirements

List of packages we used and the version we tested the model on (see also requirements.txt)

python == 3.6.8
gensim == 3.8.1
matplotlib == 3.1.1
nltk == 3.4.5
numpy == 1.16.4
pandas == 0.25.3
scipy == 1.3.2
seaborn == 0.9.0
scikit-image == 0.15.0
torch == 1.3.1
torchnet == 0.0.4
torchvision == 0.4.2
umap-learn == 0.1.1

Downloads

MNIST-SVHN Dataset

We construct a dataset of pairs of MNIST and SVHN such that each pair depicts the same digit class. Each instance of a digit class in either dataset is randomly paired with 20 instances of the same digit class from the other dataset.

Usage: To prepare this dataset, run bin/make-mnist-svhn-idx.py -- this should automatically handle the download and pairing.

CUB Image-Caption

We use Caltech-UCSD Birds (CUB) dataset, with the bird images and their captions serving as two modalities.

Usage: We offer a cleaned-up version of the CUB dataset. Download the dataset here. First, create a data folder under the project directory; then unzip thedownloaded content into data. After finishing these steps, the structure of the data/cub folder should look like:

data/cub
│───text_testclasses.txt
│───text_trainvalclasses.txt    
│───train
│   │───002.Laysan_Albatross
│   │    └───...jpg
│   │───003.Sooty_Albatross
│   │    └───...jpg
│   │───...
│   └───200.Common_Yellowthroat
│        └───...jpg
└───test
    │───001.Black_footed_Albatross
    │    └───...jpg
    │───004.Groove_billed_Ani
    │    └───...jpg
    │───...
    └───197.Marsh_Wren
         └───...jpg

Pretrained network

Pretrained models are also available if you want to play around with it. Download from the following links:

• MNIST-SVHN
• CUB Image-Caption (feature)
• CUB Image-Caption (raw images)

Usage

Training

Make sure the requirements are satisfied in your environment, and relevant datasets are downloaded. cd into src, and, for MNIST-SVHN experiments, run

python main.py --model mnist_svhn

For CUB Image-Caption with image feature search (See Figure 7 in our paper), run

python main.py --model cubISft

For CUB Image-Caption with raw image generation, run

python main.py --model cubIS

You can also play with the hyperparameters using arguments. Some of the more interesting ones are listed as follows:

• --obj: Objective functions, offers 3 choices including importance-sampled ELBO (elbo), IWAE (iwae) and DReG (dreg, used in paper). Including the --looser flag when using IWAE or DReG removes unbalanced weighting of modalities, which we find to perform better empirically;
• --K: Number of particles, controls the number of particles K in IWAE/DReG estimator, as specified in following equation:

• --learn-prior: Prior variance learning, controls whether to enable prior variance learning. Results in our paper are produced with this enabled. Excluding this argument in the command will disable this option;
• --llik_scaling: Likelihood scaling, specifies the likelihood scaling of one of the two modalities, so that the likelihoods of two modalities contribute similarly to the lower bound. The default values are:
  • MNIST-SVHN: MNIST scaling factor 32323/28281 = 3.92
  • CUB Image-Cpation: Image scaling factor 32/64643 = 0.0026
• --latent-dimension: Latent dimension

You can also load from pre-trained models by specifying the path to the model folder, for example python --model mnist_svhn --pre-trained path/to/model/folder/. See following for the flag we used for these pretrained models:

• MNIST-SVHN: --model mnist_svhn --obj dreg --K 30 --learn-prior --looser --epochs 30 --batch-size 128 --latent-dim 20
• CUB Image-Caption (feature): --model cubISft --learn-prior --K 50 --obj dreg --looser --epochs 50 --batch-size 64 --latent-dim 64 --llik_scaling 0.002
• CUB Image-Caption (raw images): --model cubIS --learn-prior --K 50 --obj dreg --looser --epochs 50 --batch-size 64 --latent-dim 64

Analysing

We offer tools to reproduce the quantitative results in our paper in src/report. To run any of the provided scripts, cd into src, and

• for likelihood estimation of data using a trained model, run python calculate_likelihoods.py --save-dir path/to/trained/model/folder/ --iwae-samples 1000;
• for coherence analysis and latent digit classification accuracy on MNIST-SVHN dataset, run python analyse_ms.py --save-dir path/to/trained/model/folder/;
• for coherence analysis on CUB image-caption dataset, run python analyse_cub.py --save-dir path/to/trained/model/folder/.
  • Note: The learnt CCA projection matrix and FastText embeddings can vary quite a bit due to the limited dataset size, therefore re-computing them as part of the analyses can result in different numeric values including for the baseline. The relative performance of our model against the baseline remains the same, just that the numbers can different. To produce similar results to what's reported in our paper, download the zip file here and do the following:
    1. Move cub.all, cub.emb, cub.pc to under data/cub/oc:3_sl:32_s:300_w:3/;
    2. Move the rest of the files, i.e. emb_mean.pt, emb_proj.pt, images_mean.pt, im_proj.pt to path/to/trained/model/folder/;
    3. Set the RESET variable in src/report/analyse_cub.py to False.

Contact

If you have any questions, feel free to create an issue or email Yuge Shi at yshi@robots.ox.ac.uk.