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# Copyright (c) Facebook, Inc. and its affiliates.
#
# This source code is licensed under the MIT license found in the
# LICENSE file in the root directory of this source tree.
import unittest
from copy import deepcopy
from dataclasses import dataclass
from typing import Optional
import torch
from fairseq.models.ema import EMA
class DummyModule(torch.nn.Module):
def __init__(self) -> None:
"""LightningModule for testing purposes
Args:
epoch_min_loss_override (int, optional): Pass in an epoch that will be set to the minimum
validation loss for testing purposes (zero based). If None this is ignored. Defaults to None.
"""
super().__init__()
self.layer = torch.nn.Linear(in_features=32, out_features=2)
self.another_layer = torch.nn.Linear(in_features=2, out_features=2)
def forward(self, x: torch.Tensor) -> torch.Tensor:
x = self.layer(x)
return self.another_layer(x)
@dataclass
class EMAConfig(object):
ema_decay: float = 0.99
ema_start_update: int = 0
ema_fp32: bool = False
ema_seed_model: Optional[str] = None
@unittest.skipIf(not torch.cuda.is_available(), "test requires a GPU")
class TestEMAGPU(unittest.TestCase):
def assertTorchAllClose(self, x, y, atol=1e-8, rtol=1e-5, msg=None):
diff = x.float() - y.float()
diff_norm = torch.norm(diff)
other_norm = torch.norm(y.float())
if msg is None:
msg = "|input - other| > {} + {} * |other|".format(
atol, rtol
)
self.assertLessEqual(
diff_norm,
atol + rtol * other_norm,
msg=msg,
)
def test_ema(self):
model = DummyModule().cuda()
optimizer = torch.optim.SGD(model.parameters(), lr=0.01)
state = deepcopy(model.state_dict())
config = EMAConfig()
ema = EMA(model, config)
# set decay
ema._set_decay(config.ema_decay)
self.assertEqual(ema.get_decay(), config.ema_decay)
# get model
self.assertEqual(ema.get_model(), ema.model)
# Since fp32 params is not used, it should be of size 0
self.assertEqual(len(ema.fp32_params), 0)
# EMA step
x = torch.randn(32).cuda()
y = model(x)
loss = y.sum()
loss.backward()
optimizer.step()
ema.step(model)
ema_state_dict = ema.get_model().state_dict()
for key, param in model.state_dict().items():
prev_param = state[key]
ema_param = ema_state_dict[key]
if "version" in key:
# Do not decay a model.version pytorch param
continue
self.assertTorchAllClose(
ema_param,
config.ema_decay * prev_param + (1 - config.ema_decay) * param,
)
# Since fp32 params is not used, it should be of size 0
self.assertEqual(len(ema.fp32_params), 0)
# Load EMA into model
model2 = DummyModule().cuda()
ema.reverse(model2)
for key, param in model2.state_dict().items():
ema_param = ema_state_dict[key]
self.assertTrue(
torch.allclose(ema_param, param)
)
def test_ema_fp32(self):
model = DummyModule().cuda().half()
optimizer = torch.optim.SGD(model.parameters(), lr=0.01)
state = deepcopy(model.state_dict())
config = EMAConfig(ema_fp32=True)
ema = EMA(model, config)
x = torch.randn(32).cuda()
y = model(x.half())
loss = y.sum()
loss.backward()
optimizer.step()
ema.step(model)
for key, param in model.state_dict().items():
prev_param = state[key]
ema_param = ema.get_model().state_dict()[key]
if "version" in key:
# Do not decay a model.version pytorch param
continue
self.assertIn(key, ema.fp32_params)
# EMA update is done in fp32, and hence the EMA param must be
# closer to the EMA update done in fp32 than in fp16.
self.assertLessEqual(
torch.norm(
ema_param.float() -
(config.ema_decay * prev_param.float() + (1 - config.ema_decay) * param.float()).half().float()
),
torch.norm(
ema_param.float() -
(config.ema_decay * prev_param + (1 - config.ema_decay) * param).float()
),
)
self.assertTorchAllClose(
ema_param,
(config.ema_decay * prev_param.float() + (1 - config.ema_decay) * param.float()).half(),
)
def test_ema_fp16(self):
model = DummyModule().cuda().half()
optimizer = torch.optim.SGD(model.parameters(), lr=0.01)
state = deepcopy(model.state_dict())
config = EMAConfig(ema_fp32=False)
ema = EMA(model, config)
# Since fp32 params is not used, it should be of size 0
self.assertEqual(len(ema.fp32_params), 0)
x = torch.randn(32).cuda()
y = model(x.half())
loss = y.sum()
loss.backward()
optimizer.step()
ema.step(model)
for key, param in model.state_dict().items():
prev_param = state[key]
ema_param = ema.get_model().state_dict()[key]
if "version" in key:
# Do not decay a model.version pytorch param
continue
# EMA update is done in fp16, and hence the EMA param must be
# closer to the EMA update done in fp16 than in fp32.
self.assertLessEqual(
torch.norm(
ema_param.float() -
(config.ema_decay * prev_param + (1 - config.ema_decay) * param).float()
),
torch.norm(
ema_param.float() -
(config.ema_decay * prev_param.float() + (1 - config.ema_decay) * param.float()).half().float()
),
)
self.assertTorchAllClose(
ema_param,
config.ema_decay * prev_param + (1 - config.ema_decay) * param,
)
# Since fp32 params is not used, it should be of size 0
self.assertEqual(len(ema.fp32_params), 0)
if __name__ == "__main__":
unittest.main()