A generic Python and TensorFlow function that implements a simple version of the "Model-Agnostic Meta-Learning (MAML) Algorithm for Fast Adaptation of Deep Networks" as designed by Chelsea Finn et al. 2017 [1]. Especially, this implementation focuses on regression and prediction problems.
- Install with
pip install simplemaml - In your python code:
from simplemaml import MAMLMAML(model=your_model, tasks=your_array_of_tasks, etc.)
- Your task should be in one of the two follwing formats:
tasks=[{"inputs": [], "target": []}, etc.]tasks=[{"train": {"inputs": [], "target": []}, "test": {"inputs": [], "target": []}}, etc.]
You can also download the lib as a .whl file using pip download simplemaml --only-binary=:all: --no-deps
- Chelsea Finn explains well her algorithm in this Standford lecture: https://www.youtube.com/watch?v=Gj5SEpFIv8I&list=PLoROMvodv4rNjRoawgt72BBNwL2V7doGI
- Original repository with a more complete version of the code: https://github.com/cbfinn/maml
- tensorflow>=2.13.0: https://www.tensorflow.org/
- numpy>=1.24.3: https://numpy.org/
Neumann, Anas. (2023). Simple Python and TensorFlow implementation of the optimization-based Model-Agnostic Meta-Learning (MAML) algorithm for supervised regression problems. GitHub repository: https://github.com/AnasNeumann/simplemaml.
@misc{simplemaml,
author = {Anas Neumann},
title = {Simple Python and TensorFlow implementation of the optimization-based Model-Agnostic Meta-Learning (MAML) algorithm for supervised regression problems},
year = {2023},
publisher = {GitHub},
journal = {GitHub repository},
howpublished = {\url{https://github.com/AnasNeumann/simplemaml}},
commit = {main}
}def MAML(model, alpha=0.005, beta=0.005, optimizer=keras.optimizers.SGD, c_loss=keras.losses.mse, f_loss=keras.losses.MeanSquaredError(), meta_epochs=100, meta_tasks_per_epoch=[10, 30], inputs_dimension=1, validation_split=0.2, k_folds=0, tasks=[], cumul=False):
"""
Simple MAML algorithm implementation for supervised regression.
:param model: A Keras model to be trained using MAML.
:param alpha: Learning rate for task-specific updates.
:param beta: Learning rate for meta-updates.
:param optimizer: Optimizer to be used for training.
:param c_loss: Loss function for calculating training loss.
:param meta_epochs: Number of meta-training epochs.
:param meta_tasks_per_epoch: Range of tasks to sample per epoch.
:param inputs_dimension: the input dimension (for sequence-to-sequence models).
:param validation_split: Ratio of data to use for validation in each task (could be fixed or random between two values).
:param k_folds: cross-validation with k_folds each time a task is called for meta-learning.
:param tasks: List of tasks for meta-training.
:param cumul: choose between sum and mean gradients during the outer loop.
:return: Tuple of trained model and evolution of losses over epochs.
"""
if "train" in tasks[0] and "test" in tasks[0]:
build_task_f = _get_task
build_task_param = {"dimension": inputs_dimension}
elif k_folds>0:
build_task_f = _k_fold_task
build_task_param = {"dimension": inputs_dimension, "k": k_folds}
else:
build_task_f = _split_task
build_task_param = {"dimension": inputs_dimension, "split": validation_split}
if tf.config.list_physical_devices('GPU'):
with tf.device('/GPU:0'):
return _MAML_compute(model, alpha, beta, optimizer, c_loss, f_loss, meta_epochs, meta_tasks_per_epoch, build_task_f, build_task_param, tasks, cumul)
else:
return _MAML_compute(model, alpha, beta, optimizer, c_loss, f_loss, meta_epochs, meta_tasks_per_epoch, build_task_f, build_task_param, tasks, cumul)
def _split_task(t, param):
d = param["dimension"]
split = param["split"]
v = random.uniform(split[0], split[1]) if isinstance(split,list) else split
split_idx = int(len(t["inputs"]) * v)
train_input = t["inputs"][:split_idx] if d<=1 else [t["inputs"][:split_idx] for _ in range(d)]
test_input = t["inputs"][split_idx:] if d<=1 else [t["inputs"][split_idx:] for _ in range(d)]
train_target, test_target = t["target"][:split_idx], t["target"][split_idx:]
return train_input, test_input, train_target, test_target
def _k_fold_task(t, param):
d = param["dimension"]
k = param["k"]
fold = random.randint(0, k-1)
fold_size = (len(t["inputs"]) // k)
v_start = fold * fold_size
v_end = (fold + 1) * fold_size if fold < k - 1 else len(t["inputs"])
t_i = np.concatenate((t["inputs"][:v_start], t["inputs"][v_end:]), axis=0)
train_input = t_i if d<=1 else [t_i for _ in range(d)]
test_input = t["inputs"][v_start:v_end] if d<=1 else [t["inputs"][v_start:v_end] for _ in range(d)]
train_target = np.concatenate((t["target"][:v_start], t["target"][v_end:]), axis=0)
test_target = t["target"][v_start:v_end]
return train_input, test_input, train_target, test_target
def _get_task(t, param):
d = param["dimension"]
train_input = t["train"]["inputs"] if d<=1 else [t["train"]["inputs"] for _ in range(d)]
test_input = t["test"]["inputs"] if d<=1 else [t["test"]["inputs"] for _ in range(d)]
return train_input, test_input, t["train"]["target"], t["test"]["target"]
def _MAML_compute(model, alpha, beta, optimizer, c_loss, f_loss, meta_epochs, meta_tasks_per_epoch, build_task_f, build_task_param, tasks, cumul):
log_step = meta_epochs // 10 if meta_epochs > 10 else 1
optim_test=optimizer(learning_rate=alpha)
optim_train=optimizer(learning_rate=beta)
model_copy = tf.keras.models.clone_model(model)
model_copy.build(model.input_shape)
model_copy.set_weights(model.get_weights())
optim_test.build(model.trainable_variables)
optim_train.build(model_copy.trainable_variables)
model.compile(loss=f_loss, optimizer=optim_test)
model_copy.compile(loss=f_loss, optimizer=optim_train)
losses=[]
total_loss=0.
for step in range (meta_epochs):
sum_gradients = [tf.zeros_like(variable) for variable in model.trainable_variables]
num_tasks_sampled = random.randint(meta_tasks_per_epoch[0], meta_tasks_per_epoch[1])
model_copy.set_weights(model.get_weights())
for _ in range(num_tasks_sampled):
train_input, test_input, train_target, test_target = build_task_f(random.choice(tasks), build_task_param)
# 1. Inner loop: Update the model copy on the current task
with tf.GradientTape(watch_accessed_variables=False) as train_tape:
train_tape.watch(model_copy.trainable_variables)
train_pred = model_copy(train_input)
train_loss = tf.reduce_mean(c_loss(train_target, train_pred))
g = train_tape.gradient(train_loss, model_copy.trainable_variables)
optim_train.apply_gradients(zip(g, model_copy.trainable_variables))
# 2. Compute gradients with respect to the test data
with tf.GradientTape(watch_accessed_variables=False) as test_tape:
test_tape.watch(model_copy.trainable_variables)
test_pred = model_copy(test_input)
test_loss = tf.reduce_mean(c_loss(test_target, test_pred))
g = test_tape.gradient(test_loss, model_copy.trainable_variables)
for i, gradient in enumerate(g):
sum_gradients[i] += gradient
# 3. Meta-update: apply the accumulated gradients to the original model
cumul_gradients = [grad / (1.0 if cumul else num_tasks_sampled) for grad in sum_gradients]
optim_test.apply_gradients(zip(cumul_gradients, model.trainable_variables))
total_loss += test_loss.numpy()
loss_evol = total_loss/(step+1)
losses.append(loss_evol)
if step % log_step == 0:
print(f'Meta epoch: {step+1}/{meta_epochs}, Loss: {loss_evol}')
return model, lossesrm -rf dist/ build/ simplemaml.egg-info/python3 setup.py sdist bdist_wheeltwine upload dist/*
[1] Finn, C., Abbeel, P. & Levine, S.. (2017). Model-Agnostic Meta-Learning for Fast Adaptation of Deep Networks. Proceedings of the 34th International Conference on Machine Learning, in Proceedings of Machine Learning Research 70:1126-1135 Available from https://proceedings.mlr.press/v70/finn17a.html and https://proceedings.mlr.press/v70/finn17a/finn17a.pdf.