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# Copyright 2024 EPFL and Apple Inc.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
# --------------------------------------------------------
# Based on DINO code base
# https://github.com/facebookresearch/dino
# --------------------------------------------------------
import numpy as np
import math
def cosine_scheduler(base_value, final_value, epochs, niter_per_ep, warmup_epochs=0,
start_warmup_value=0, warmup_steps=-1):
warmup_schedule = np.array([])
warmup_iters = warmup_epochs * niter_per_ep
if warmup_steps > 0:
warmup_iters = warmup_steps
print("Set warmup steps = %d" % warmup_iters)
if warmup_epochs > 0 or warmup_steps > 0:
warmup_schedule = np.linspace(start_warmup_value, base_value, warmup_iters)
iters = np.arange(epochs * niter_per_ep - warmup_iters)
schedule = np.array(
[final_value + 0.5 * (base_value - final_value) * (1 + math.cos(math.pi * i / (len(iters)))) for i in iters])
schedule = np.concatenate((warmup_schedule, schedule))
assert len(schedule) == epochs * niter_per_ep
return schedule
def constant_scheduler(base_value, epochs, niter_per_ep):
return base_value * np.ones(epochs*niter_per_ep)
def inverse_sqrt_scheduler(base_value, final_value, epochs, niter_per_ep, warmup_epochs=0,
start_warmup_value=0, warmup_steps=-1,
cooldown_epochs=0, cooldown_steps=-1,
timescale=10_000):
warmup_iters = warmup_epochs * niter_per_ep
if warmup_steps > 0:
warmup_iters = warmup_steps
print("Set warmup steps = %d" % warmup_iters)
cooldown_iters = cooldown_epochs * niter_per_ep
if cooldown_steps > 0:
cooldown_iters = cooldown_steps
print("Set cooldown steps = %d" % cooldown_iters)
# Warmup schedule
if warmup_epochs > 0 or warmup_steps > 0:
warmup_schedule = np.linspace(start_warmup_value, base_value, warmup_iters)
else:
warmup_schedule = np.array([])
# Inverse square-root LR schedule
iters = np.arange(epochs * niter_per_ep - warmup_iters - cooldown_iters)
if base_value == final_value:
schedule = base_value * np.ones(len(iters))
else:
schedule = base_value / np.sqrt((iters + timescale) / timescale)
# Cooldown schedule
if cooldown_epochs > 0 or cooldown_steps > 0:
cooldown_schedule = np.linspace(schedule[-1], final_value, cooldown_iters)
else:
cooldown_schedule = np.array([])
schedule = np.concatenate((warmup_schedule, schedule, cooldown_schedule))
assert len(schedule) == epochs * niter_per_ep
return schedule