def test_per_sample_grads_embeddingnet(self, device):
class SampleNet(nn.Module):
def __init__(self, vocab_size: int):
super().__init__()
self.emb = nn.Embedding(vocab_size, 16)
self.fc1 = nn.Linear(16, 16)
self.fc2 = nn.Linear(16, 2)
def forward(self, x):
x = self.emb(x)
x = torch.transpose(x, -1, -2)
x = torch.mean(x, -1)
x = self.fc1(x)
x = F.relu(x)
x = self.fc2(x)
return x
def name(self):
return "SampleNet"
# Create our inputs...
vocab_size = 1000
batch_shape = [64]
words_per_sentence = 5
data = torch.randint(0, vocab_size, (*batch_shape, words_per_sentence), device=device)
targets = torch.randint(0, 1, (*batch_shape,), device=device)
# Construct our module
net = SampleNet(vocab_size).to(device=device)
criterion = nn.CrossEntropyLoss()
params = dict(net.named_parameters())
weights, net_func, _ = make_functional(net)
def compute_loss(weights, data, target):
output = net_func(weights, (data,))
result = criterion(output, target)
return result
expected = [grad(compute_loss)(weights, data[i], targets[i]) for i in range(64)]
expected = zip(*expected)
expected = tuple(torch.stack(shards) for shards in expected)
result = vmap(partial(grad(compute_loss), weights))(data, targets)
for r, e in zip(result, expected):
# TODO: Check if the rtol is a problem
self.assertEqual(r, e, atol=0, rtol=1e-4)
self.mod = nn.Sequential(*mods)
def forward(self, x):
return (self.mod(x)**2).sum()
batch_size = 16
features = 64
num_layers = 8
inp = torch.randn((batch_size, features))
mod = Foo(num_layers, features)
jit_mod = torch.jit.script(mod)
func_model, weights = make_functional(mod)
lr = 1.0
def functional_step(x, weights):
weights = [weight.detach().requires_grad_() for weight in weights]
out = func_model(weights, x)
out.backward()
new_weights = [weight - lr * weight.grad for weight in weights]
return out, new_weights
optim = torch.optim.SGD(jit_mod.parameters(),
lr=lr,
momentum=0,
dampening=0,
self.fc2 = nn.Linear(self.hidden_dim, self.n_classes)
def forward(self, x):
x = self.fc1(x)
x = F.relu(x)
x = self.fc2(x)
x = F.log_softmax(x, -1)
return x
loss_fn = nn.NLLLoss()
# Step 3: Make the model functional(!!) and define a training function.
# NB: this mechanism doesn't exist in PyTorch today, but we want it to:
# https://github.com/pytorch/pytorch/issues/49171
func_model, weights = make_functional(MLPClassifier().to(DEVICE))
def train_step_fn(weights, batch, targets, lr=0.2):
def compute_loss(weights, batch, targets):
output = func_model(weights, batch)
loss = loss_fn(output, targets)
return loss
grad_weights, loss = grad_and_value(compute_loss)(weights, batch, targets)
# NB: PyTorch is missing a "functional optimizer API" (possibly coming soon)
# so we are going to re-implement SGD here.
new_weights = []
with torch.no_grad():
for grad_weight, weight in zip(grad_weights, weights):
x = self.fc1(x)
x = self.relu1(x)
x = self.fc2(x)
x = self.relu2(x)
x = self.fc3(x)
return x
# TODO: Use F.mse_loss
def mse_loss(x, y):
return torch.mean((x - y)**2)
net, params = make_functional(ThreeLayerNet())
opt = torch.optim.Adam(params, lr=1e-3)
alpha = 0.1
K = 20
losses = []
num_tasks = 4
def sample_tasks(outer_batch_size, inner_batch_size):
# Select amplitude and phase for the task
As = []
phases = []
for _ in range(outer_batch_size):
As.append(np.random.uniform(low=0.1, high=.5))
phases.append(np.random.uniform(low=0., high=np.pi))
def forward(self, x):
x = self.fc1(x)
x = self.relu1(x)
x = self.fc2(x)
x = self.relu2(x)
x = self.fc3(x)
return x
# The prototype doesn't like F.mse_loss.
def mse_loss(x, y):
return torch.mean((x - y)**2)
params, net, _ = make_functional(ThreeLayerNet())
opt = torch.optim.Adam(params, lr=1e-3)
alpha = 0.1
K = 20
losses = []
num_tasks = 4
def sample_tasks(outer_batch_size, inner_batch_size):
# Select amplitude and phase for the task
As = []
phases = []
for _ in range(outer_batch_size):
As.append(np.random.uniform(low=0.1, high=.5))
phases.append(np.random.uniform(low=0., high=np.pi))
def test_resnet18_per_sample_grads(self, device):
# Straight out of opacus
def _replace_child(
root: nn.Module, child_name: str, converter: Callable[[nn.Module], nn.Module]
) -> None:
# find the immediate parent
parent = root
nameList = child_name.split(".")
for name in nameList[:-1]:
parent = parent._modules[name]
# set to identity
parent._modules[nameList[-1]] = converter(parent._modules[nameList[-1]])
def replace_all_modules(
root: nn.Module,
target_class: Type[nn.Module],
converter: Callable[[nn.Module], nn.Module],
) -> nn.Module:
# base case
if isinstance(root, target_class):
return converter(root)
for name, obj in root.named_modules():
if isinstance(obj, target_class):
_replace_child(root, name, converter)
return root
def _batchnorm_to_groupnorm(module: nn.modules.batchnorm._BatchNorm) -> nn.Module:
return nn.GroupNorm(min(32, module.num_features), module.num_features, affine=True)
def convert_batchnorm_modules(
model: nn.Module,
converter: Callable[
[nn.modules.batchnorm._BatchNorm], nn.Module
] = _batchnorm_to_groupnorm,
) -> nn.Module:
return replace_all_modules(model, nn.modules.batchnorm._BatchNorm, converter)
import torchvision.models as models
model = convert_batchnorm_modules(models.resnet18(num_classes=10)).to(device)
criterion = nn.CrossEntropyLoss()
weights, func_model, descriptors = make_functional(model)
def compute_loss(weights, image, target):
images = image.unsqueeze(0)
targets = target.unsqueeze(0)
output = func_model(weights, (images,))
loss = criterion(output, targets)
return loss
batch_size = 3
images = torch.randn(batch_size, 3, 32, 32, device=device)
targets = torch.randint(0, 10, (batch_size,), device=device)
result_grads = vmap(grad(compute_loss), in_dims=(None, 0, 0))(weights, images, targets)
expected_grads = [
torch.autograd.grad(compute_loss(weights, images[i], targets[i]), weights)
for i in range(batch_size)
]
expected_grads = [torch.stack(shards) for shards in zip(*expected_grads)]
self.assertEqual(result_grads, expected_grads)
def init_fn(num_models):
models = tuple(MLPClassifier().to(device) for _ in range(num_models))
weights = tuple(make_functional(model)[0] for model in models)
weights = tuple(zip(*weights))
weights = tuple(torch.stack(shards).detach() for shards in weights)
return weights
def test_ensemble_regression(self, device):
def make_spirals(n_samples, noise_std=0., rotations=1.):
ts = torch.linspace(0, 1, n_samples)
rs = ts ** 0.5
thetas = rs * rotations * 2 * math.pi
signs = torch.randint(0, 2, (n_samples,)) * 2 - 1
labels = (signs > 0).to(torch.long)
xs = rs * signs * torch.cos(thetas) + torch.randn(n_samples) * noise_std
ys = rs * signs * torch.sin(thetas) + torch.randn(n_samples) * noise_std
points = torch.stack([xs, ys], dim=1)
return points.to(device), labels.to(device)
points, labels = make_spirals(100, noise_std=0.05)
class MLPClassifier(nn.Module):
def __init__(self, hidden_dim=32, n_classes=2):
super().__init__()
self.hidden_dim = hidden_dim
self.n_classes = n_classes
self.fc1 = nn.Linear(2, self.hidden_dim)
self.fc2 = nn.Linear(self.hidden_dim, self.n_classes)
def forward(self, x):
x = self.fc1(x)
x = F.relu(x)
x = self.fc2(x)
x = F.log_softmax(x, -1)
return x
loss_fn = nn.NLLLoss()
weights, func_model, _ = make_functional(MLPClassifier().to(device))
def train_step_fn(use_transform, weights, batch, targets, lr=0.2):
def compute_loss(weights, batch, targets):
output = func_model(weights, (batch,))
loss = loss_fn(output, targets)
return loss
if use_transform:
grad_weights, loss = grad_and_value(compute_loss)(weights, batch, targets)
else:
loss = compute_loss(weights, batch, targets)
grad_weights = torch.autograd.grad(loss, weights)
new_weights = []
with torch.no_grad():
for grad_weight, weight in zip(grad_weights, weights):
new_weights.append(weight - grad_weight * lr)
# NB: return looks weird because torch.vmap must return Tensors
return (loss, *new_weights)
def unpack(train_result):
return train_result[0], train_result[1:]
def init_fn(num_models):
models = tuple(MLPClassifier().to(device) for _ in range(num_models))
weights = tuple(make_functional(model)[0] for model in models)
weights = tuple(zip(*weights))
weights = tuple(torch.stack(shards).detach() for shards in weights)
return weights
def slice_weights(batched_weights, index):
return tuple(weight[index].detach().requires_grad_() for weight in batched_weights)
batched_weights = init_fn(num_models=2)
parallel_train_step_fn = vmap(partial(train_step_fn, True), in_dims=(0, None, None))
result_loss, result_weights = unpack(parallel_train_step_fn(batched_weights, points, labels))
loss0, weights0 = unpack(train_step_fn(False, slice_weights(batched_weights, 0), points, labels))
loss1, weights1 = unpack(train_step_fn(False, slice_weights(batched_weights, 1), points, labels))
expected_loss = torch.stack([loss0, loss1])
expected_weights = tuple(torch.stack([w0, w1]) for w0, w1 in zip(weights0, weights1))
self.assertEqual(result_loss, expected_loss)
self.assertEqual(result_weights, expected_weights)
def test_maml_regression(self, device):
class ThreeLayerNet(nn.Module):
def __init__(self):
super(ThreeLayerNet, self).__init__()
self.fc1 = nn.Linear(1, 40)
self.relu1 = nn.ReLU()
self.fc2 = nn.Linear(40, 40)
self.relu2 = nn.ReLU()
self.fc3 = nn.Linear(40, 1)
def forward(self, x):
x = self.fc1(x)
x = self.relu1(x)
x = self.fc2(x)
x = self.relu2(x)
x = self.fc3(x)
return x
# The prototype doesn't like F.mse_loss.
def mse_loss(x, y):
return torch.mean((x - y) ** 2)
params, net, _ = make_functional(ThreeLayerNet().to(device))
K = 20
losses = []
num_tasks = 4
alpha = 0.1
def sample_tasks(outer_batch_size, inner_batch_size):
# Select amplitude and phase for the task
As = []
phases = []
for _ in range(outer_batch_size):
As.append(np.random.uniform(low=0.1, high=.5))
phases.append(np.random.uniform(low=0., high=np.pi))
def get_batch():
xs, ys = [], []
for A, phase in zip(As, phases):
x = np.random.uniform(low=-5., high=5., size=(inner_batch_size, 1))
y = A * np.sin(x + phase)
xs.append(x)
ys.append(y)
return torch.tensor(xs, dtype=torch.float, device=device), \
torch.tensor(ys, dtype=torch.float, device=device)
x1, y1 = get_batch()
x2, y2 = get_batch()
return x1, y1, x2, y2
def get_loss_for_task(use_transform, x1, y1, x2, y2):
def inner_loss(params, x1, y1):
f = net(params, (x1,))
loss = mse_loss(f, y1)
return loss
if use_transform:
grads = grad(inner_loss)(params, x1, y1)
else:
loss = inner_loss(params, x1, y1)
grads = torch.autograd.grad(loss, params, create_graph=True)
new_params = [(params[i] - alpha*grads[i]) for i in range(len(params))]
v_f = net(new_params, (x2,))
return mse_loss(v_f, y2)
task = sample_tasks(num_tasks, K)
# Compute with vmap+grad
inner_losses = vmap(partial(get_loss_for_task, True))\
(task[0], task[1], task[2], task[3])
loss2 = sum(inner_losses)/len(inner_losses)
result_grads = torch.autograd.grad(loss2, params)
# Compute without vmap+grad
inner_losses = [
get_loss_for_task(False, task[0][i], task[1][i], task[2][i], task[3][i])
for i in range(num_tasks)
]
loss2 = sum(inner_losses)/len(inner_losses)
expected_grads = torch.autograd.grad(loss2, params)
self.assertEqual(result_grads, expected_grads)
def train(args, model, train_loader, optimizer, epoch, device):
start_time = datetime.now()
criterion = nn.CrossEntropyLoss()
losses = []
top1_acc = []
for i, (images, target) in enumerate(tqdm(train_loader)):
images = images.to(device)
target = target.to(device)
# Step 1: compute per-sample-grads
# In order to use functional vmap+grad, we need to be able to
# pass the weights to a model.
func_model, weights = make_functional(model)
# To use vmap+grad to compute per-sample-grads, the forward pass
# must be re-formulated on a single example.
# We use the `grad` operator to compute forward+backward on a single example,
# and finally `vmap` to do forward+backward on multiple examples.
def compute_loss_and_output(weights, image, target):
images = image.unsqueeze(0)
targets = target.unsqueeze(0)
output = func_model(weights, images)
loss = criterion(output, targets)
return loss, output.squeeze(0)
# `grad(f)` is a functional API that returns a function `f'` that
# computes gradients by running both the forward and backward pass.
# We want to extract some intermediate
# values from the computation (i.e. the loss and output).
#
# To extract the loss, we use the `grad_and_value` API, that returns the
# gradient of the weights w.r.t. the loss and the loss.
#
# To extract the output, we use the `has_aux=True` flag.
# `has_aux=True` assumes that `f` returns a tuple of two values,
# where the first is to be differentiated and the second "auxiliary value"
# is not to be differentiated. `f'` returns the gradient w.r.t. the loss,
# the loss, and the auxiliary value.
grads_loss_output = grad_and_value(compute_loss_and_output,
has_aux=True)
sample_grads, (sample_loss, output) = \
vmap(grads_loss_output, (None, 0, 0))(weights, images, target)
loss = sample_loss.mean()
for grad_sample, weight in zip(sample_grads, model.parameters()):
weight.grad_sample = grad_sample.detach()
# Step 2: Clip the per-sample-grads, sum them to form grads, and add noise
clip_and_accumulate_and_add_noise(model, args.max_per_sample_grad_norm,
args.sigma)
preds = np.argmax(output.detach().cpu().numpy(), axis=1)
labels = target.detach().cpu().numpy()
losses.append(loss.item())
# measure accuracy and record loss
acc1 = accuracy(preds, labels)
top1_acc.append(acc1)
# make sure we take a step after processing the last mini-batch in the
# epoch to ensure we start the next epoch with a clean state
optimizer.step()
optimizer.zero_grad()
if i % args.print_freq == 0:
print(f"\tTrain Epoch: {epoch} \t"
f"Loss: {np.mean(losses):.6f} "
f"Acc@1: {np.mean(top1_acc):.6f} ")
train_duration = datetime.now() - start_time
return train_duration
self.mod = nn.Sequential(*mods)
def forward(self, x):
return (self.mod(x)**2).sum()
batch_size = 16
features = 64
num_layers = 8
inp = torch.randn((batch_size, features))
mod = Foo(num_layers, features)
jit_mod = torch.jit.script(mod)
weights, func_model, _ = make_functional(mod)
lr = 1.0
def functional_step(x, weights):
grads, value = grad_and_value(func_model)(weights, (x, ))
new_weights = [
weight - lr * p_grad for p_grad, weight in zip(grads, weights)
]
return value, new_weights
optim = torch.optim.SGD(jit_mod.parameters(),
lr=lr,
momentum=0,
dampening=0,