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70 lines
2.1 KiB
Python
70 lines
2.1 KiB
Python
#!/usr/bin/python
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# -*- encoding: utf-8 -*-
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import torch
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import logging
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logger = logging.getLogger()
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class Optimizer(object):
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def __init__(self,
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model,
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lr0,
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momentum,
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wd,
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warmup_steps,
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warmup_start_lr,
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max_iter,
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power,
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*args, **kwargs):
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self.warmup_steps = warmup_steps
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self.warmup_start_lr = warmup_start_lr
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self.lr0 = lr0
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self.lr = self.lr0
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self.max_iter = float(max_iter)
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self.power = power
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self.it = 0
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wd_params, nowd_params, lr_mul_wd_params, lr_mul_nowd_params = model.get_params()
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param_list = [
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{'params': wd_params},
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{'params': nowd_params, 'weight_decay': 0},
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{'params': lr_mul_wd_params, 'lr_mul': True},
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{'params': lr_mul_nowd_params, 'weight_decay': 0, 'lr_mul': True}]
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self.optim = torch.optim.SGD(
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param_list,
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lr = lr0,
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momentum = momentum,
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weight_decay = wd)
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self.warmup_factor = (self.lr0/self.warmup_start_lr)**(1./self.warmup_steps)
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def get_lr(self):
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if self.it <= self.warmup_steps:
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lr = self.warmup_start_lr*(self.warmup_factor**self.it)
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else:
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factor = (1-(self.it-self.warmup_steps)/(self.max_iter-self.warmup_steps))**self.power
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lr = self.lr0 * factor
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return lr
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def step(self):
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self.lr = self.get_lr()
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for pg in self.optim.param_groups:
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if pg.get('lr_mul', False):
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pg['lr'] = self.lr * 10
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else:
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pg['lr'] = self.lr
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if self.optim.defaults.get('lr_mul', False):
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self.optim.defaults['lr'] = self.lr * 10
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else:
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self.optim.defaults['lr'] = self.lr
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self.it += 1
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self.optim.step()
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if self.it == self.warmup_steps+2:
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logger.info('==> warmup done, start to implement poly lr strategy')
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def zero_grad(self):
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self.optim.zero_grad()
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