Learn2learn

For more algorithms (ProtoNets, ANIL, Meta-SGD, Reptile, Meta-Curvature, KFO) refer to the examples folder. Most of them can be implemented with with the GBML wrapper. (documentation).

maml = l2l.algorithms.MAML(model, lr=0.1)
opt = torch.optim.SGD(maml.parameters(), lr=0.001)
for iteration in range(10):
    opt.zero_grad()
    task_model = maml.clone()  # torch.clone() for nn.Modules
    adaptation_loss = compute_loss(task_model)
    task_model.adapt(adaptation_loss)  # computes gradient, update task_model in-place
    evaluation_loss = compute_loss(task_model)
    evaluation_loss.backward()  # gradients w.r.t. maml.parameters()
    opt.step()

Learn any kind of optimization algorithm with the LearnableOptimizer. (example and documentation)

linear = nn.Linear(784, 10)
transform = l2l.optim.ModuleTransform(l2l.nn.Scale)
metaopt = l2l.optim.LearnableOptimizer(linear, transform, lr=0.01)  # metaopt has .step()
opt = torch.optim.SGD(metaopt.parameters(), lr=0.001)  # metaopt also has .parameters()

metaopt.zero_grad()
opt.zero_grad()
error = loss(linear(X), y)
error.backward()
opt.step()  # update metaopt
metaopt.step()  # update linear

Many standardized datasets (Omniglot, mini-/tiered-ImageNet, FC100, CIFAR-FS) are readily available in learn2learn.vision.datasets. (documentation)

dataset = l2l.data.MetaDataset(MyDataset())  # any PyTorch dataset
transforms = [  # Easy to define your own transform
    l2l.data.transforms.NWays(dataset, n=5),
    l2l.data.transforms.KShots(dataset, k=1),
    l2l.data.transforms.LoadData(dataset),
]
taskset = TaskDataset(dataset, transforms, num_tasks=20000)
for task in taskset:
    X, y = task
    # Meta-train on the task

Parallelize your own meta-environments with AsyncVectorEnv, or use the standardized ones. (documentation)

def make_env():
    env = l2l.gym.HalfCheetahForwardBackwardEnv()
    env = cherry.envs.ActionSpaceScaler(env)
    return env

env = l2l.gym.AsyncVectorEnv([make_env for _ in range(16)])  # uses 16 threads
for task_config in env.sample_tasks(20):
    env.set_task(task)  # all threads receive the same task
    state = env.reset()  # use standard Gym API
    action = my_policy(env)
    env.step(action)

Learn and differentiate through updates of PyTorch Modules. (documentation)

model = MyModel()
transform = l2l.optim.KroneckerTransform(l2l.nn.KroneckerLinear)
learned_update = l2l.optim.ParameterUpdate(  # learnable update function
        model.parameters(), transform)
clone = l2l.clone_module(model)  # torch.clone() for nn.Modules
error = loss(clone(X), y)
updates = learned_update(  # similar API as torch.autograd.grad
    error,
    clone.parameters(),
    create_graph=True,
)
l2l.update_module(clone, updates=updates)
loss(clone(X), y).backward()  # Gradients w.r.t model.parameters() and learned_update.parameters()