PyTorch implementation of the "ANML" algorithm (paper, code) using the higher framework.

Overview

The "training" of a few-shots meta-learned model like ANML consists of:

• train-train: the model is shown a random (initially new) task, i.e. 20 chars from one Omniglot class (a.k.a. learning phase)
• train-test: the model is tested on the last task it has just trained on and a sample of 64 random images from all the classes (a.k.a. remembering phase)
• test-train: at test time the model is shown a few examples (15) of a new class not seen during train-train. Labels are also provided and the model is asked to quickly learn this new class without forgetting (for 600 the learning sequence is 9000 gradient updates long)
• test-test: after learning from the few-shots the model performance is evaluated on the holdout examples.

The code for these phases can be found inside this file.

Prerequisites

• Python >=3.5
• PyTorch >=1.6.0
• higher
• numpy
• scikit-learn
• tqdm

Creating Your Virtual Environment

To get you set up faster, we support creating a Python environment directly from dependency files.

Conda

If you have Anaconda or Miniconda, navigate to the higherANML repo and run:

$  conda env create -n higherANML -f environment.yml
$  conda activate higherANML

If you want to name the environment differently, replace higherANML in the above lines with your custom name.

This file can be re-generated by: (1) running conda env export --from-history > environment.yml, (2) manually deleting the prefix: field, (3) adding the necessary pip packages.

Pip

To use classic Python tooling, navigate to the higherANML repo and run:

$  python -m venv .venv
$  source .venv/bin/activate
$  pip install -r requirements.txt

This assumes you want to store the virtual environment locally within the repo, as is common practice with venv. If you have errors and do not have the latest pip, try upgrading to see if that fixes the issue: python -m pip install --upgrade pip.

This file should be manually kept in sync when new dependencies are added.

Pipenv

We do not currently support pipenv because this author could not get it to install PyTorch correctly. But if you get a working Pipfile please do contribute!

Training

Phase	Trained	Optimizer	LR
inner loop	rln + fc	SGD	0.1
outer loop	everything	Adam	0.003

Training can be performed using

python train_omni.py

flags can be provided for exploring different setups.

Evaluation

Number of tasks	Accuracy	Eval LR
10	0.90	0.0010
50	0.89	0.0010
75	0.86	0.0010
100	0.85	0.0010
200	0.80	0.0008
300	0.76	0.0008
400	0.72	0.0008
600	0.65	0.0008

Evaluation can be performed using

python eval_omni.py --model trained_anmls/256_112_2304_ANML-29999.pth --classes 10 --lr 0.00085 --runs 10

During evaluation the model is quite sensitive to learning rates used, the data shown in the above table has been gathered sweeping several learning rates over multiple repeats.