34 lines
1.1 KiB
Python
34 lines
1.1 KiB
Python
from math import cos, pi
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from mmcv.runner import Hook
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from .registry import HOOKS
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@HOOKS.register_module
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class BYOLHook(Hook):
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"""Hook for BYOL.
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This hook includes momentum adjustment in BYOL following:
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m = 1 - ( 1- m_0) * (cos(pi * k / K) + 1) / 2,
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k: current step, K: total steps.
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Args:
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end_momentum (float): The final momentum coefficient
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for the target network. Default: 1.
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"""
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def __init__(self, end_momentum=1., **kwargs):
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self.end_momentum = end_momentum
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def before_train_iter(self, runner):
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assert hasattr(runner.model.module, 'momentum'), \
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"The runner must have attribute \"momentum\" in BYOLHook."
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assert hasattr(runner.model.module, 'base_momentum'), \
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"The runner must have attribute \"base_momentum\" in BYOLHook."
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cur_iter = runner.iter
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max_iter = runner.max_iters
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base_m = runner.model.module.base_momentum
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m = self.end_momentum - (self.end_momentum - base_m) * (
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cos(pi * cur_iter / float(max_iter)) + 1) / 2
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runner.model.module.momentum = m
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