217 lines
9.1 KiB
Python
217 lines
9.1 KiB
Python
import math
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from collections import Counter
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from collections import defaultdict
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import torch
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from torch.optim.lr_scheduler import _LRScheduler
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from utils.util import opt_get
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def get_scheduler_for_name(name, optimizers, scheduler_opt):
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schedulers = []
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for o in optimizers:
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# Hack to support LARC, which wraps an underlying optimizer.
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if hasattr(o, 'optim'):
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o = o.optim
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if name == 'MultiStepLR':
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sched = MultiStepLR_Restart(o, scheduler_opt['gen_lr_steps'],
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restarts=scheduler_opt['restarts'],
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weights=scheduler_opt['restart_weights'],
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gamma=scheduler_opt['lr_gamma'],
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clear_state=scheduler_opt['clear_state'],
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force_lr=scheduler_opt['force_lr'],
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warmup_steps=opt_get(scheduler_opt, ['warmup_steps'], 0))
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elif name == 'ProgressiveMultiStepLR':
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sched = ProgressiveMultiStepLR(o, scheduler_opt['gen_lr_steps'],
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scheduler_opt['progressive_starts'],
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scheduler_opt['lr_gamma'])
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elif name == 'CosineAnnealingLR_Restart':
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sched = CosineAnnealingLR_Restart(
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o, scheduler_opt['T_period'], scheduler_opt['warmup'], eta_min=scheduler_opt['eta_min'],
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restarts=scheduler_opt['restarts'], weights=scheduler_opt['restart_weights'])
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else:
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raise NotImplementedError('Scheduler not available')
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schedulers.append(sched)
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return schedulers
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# This scheduler is specifically designed to modulate the learning rate of several different param groups configured
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# by a generator or discriminator that slowly adds new stages one at a time, e.g. like progressive growing of GANs.
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class ProgressiveMultiStepLR(_LRScheduler):
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def __init__(self, optimizer, milestones, group_starts, gamma=0.1):
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self.milestones = Counter(milestones)
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self.gamma = gamma
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self.group_starts = group_starts
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super(ProgressiveMultiStepLR, self).__init__(optimizer)
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def get_lr(self):
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group_lrs = []
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assert len(self.optimizer.param_groups) == len(self.group_starts)
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for group, group_start in zip(self.optimizer.param_groups, self.group_starts):
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if self.last_epoch - group_start not in self.milestones:
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group_lrs.append(group['lr'])
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else:
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group_lrs.append(group['lr'] * self.gamma)
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return group_lrs
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class MultiStepLR_Restart(_LRScheduler):
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def __init__(self, optimizer, milestones, restarts=None, weights=None, gamma=0.1,
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clear_state=False, force_lr=False, last_epoch=-1, warmup_steps=0):
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self.milestones = Counter(milestones)
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self.gamma = gamma
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self.clear_state = clear_state
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self.restarts = restarts if restarts else [0]
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self.restarts = [v + 1 for v in self.restarts]
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self.restart_weights = weights if weights else [1]
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self.force_lr = force_lr
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if force_lr:
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print(f"!!Forcing the learning rate to: {force_lr}")
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self.warmup_steps = warmup_steps
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assert len(self.restarts) == len(
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self.restart_weights), 'restarts and their weights do not match.'
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super(MultiStepLR_Restart, self).__init__(optimizer, last_epoch)
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def get_lr(self):
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# Note to self: for the purposes of this trainer, "last_epoch" should read "last_step"
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if self.force_lr is not None:
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return [self.force_lr for _ in self.optimizer.param_groups]
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if self.last_epoch in self.restarts:
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if self.clear_state:
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self.optimizer.state = defaultdict(dict)
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weight = self.restart_weights[self.restarts.index(self.last_epoch)]
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return [group['initial_lr'] * weight for group in self.optimizer.param_groups]
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if self.last_epoch < self.warmup_steps:
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factor = 1 - (self.warmup_steps - self.last_epoch) / self.warmup_steps
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return [group['initial_lr'] * factor for group in self.optimizer.param_groups]
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if self.last_epoch not in self.milestones:
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return [group['lr'] for group in self.optimizer.param_groups]
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return [
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group['lr'] * self.gamma**self.milestones[self.last_epoch]
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for group in self.optimizer.param_groups
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]
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# Allow this scheduler to use newly appointed milestones partially through a training run..
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def load_state_dict(self, s):
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milestones_cache = self.milestones
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force_lr_cache = self.force_lr
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super(MultiStepLR_Restart, self).load_state_dict(s)
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self.milestones = milestones_cache
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self.force_lr = force_lr_cache
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class CosineAnnealingLR_Restart(_LRScheduler):
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def __init__(self, optimizer, T_period, warmup=0, restarts=None, weights=None, eta_min=0, last_epoch=-1):
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self.warmup = warmup
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self.T_period = T_period
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self.T_max = self.T_period[0] # current T period
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self.eta_min = eta_min
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self.restarts = restarts if restarts else [0]
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self.restarts = [v + 1 for v in self.restarts]
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self.restart_weights = weights if weights else [1]
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self.last_restart = 0
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assert len(self.restarts) == len(
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self.restart_weights), 'restarts and their weights do not match.'
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super(CosineAnnealingLR_Restart, self).__init__(optimizer, last_epoch)
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def get_lr(self):
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step = self.last_epoch - self.warmup
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if step <= 0:
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return self.base_lrs
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elif step in self.restarts:
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self.last_restart = step
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self.T_max = self.T_period[self.restarts.index(step) + 1]
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weight = self.restart_weights[self.restarts.index(step)]
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return [group['initial_lr'] * weight for group in self.optimizer.param_groups]
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elif (step - self.last_restart - 1 - self.T_max) % (2 * self.T_max) == 0:
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return [
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group['lr'] + (base_lr - self.eta_min) * (1 - math.cos(math.pi / self.T_max)) / 2
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for base_lr, group in zip(self.base_lrs, self.optimizer.param_groups)
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]
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return [(1 + math.cos(math.pi * (step - self.last_restart) / self.T_max)) /
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(1 + math.cos(math.pi * ((step - self.last_restart) - 1) / self.T_max)) *
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(group['lr'] - self.eta_min) + self.eta_min
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for group in self.optimizer.param_groups]
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if __name__ == "__main__":
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optimizer = torch.optim.Adam([torch.zeros(3, 64, 3, 3)], lr=1e-4, weight_decay=0,
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betas=(0.9, 0.99))
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##############################
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# MultiStepLR_Restart
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##############################
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## Original
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lr_steps = [200000, 400000, 600000, 800000]
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restarts = None
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restart_weights = None
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## two
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lr_steps = [100000, 200000, 300000, 400000, 490000, 600000, 700000, 800000, 900000, 990000]
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restarts = [500000]
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restart_weights = [1]
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## four
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lr_steps = [
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50000, 100000, 150000, 200000, 240000, 300000, 350000, 400000, 450000, 490000, 550000,
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600000, 650000, 700000, 740000, 800000, 850000, 900000, 950000, 990000
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]
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restarts = [250000, 500000, 750000]
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restart_weights = [1, 1, 1]
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scheduler = MultiStepLR_Restart(optimizer, lr_steps, restarts, restart_weights, gamma=0.5,
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clear_state=False, warmup_steps=20000)
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'''
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##############################
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# Cosine Annealing Restart
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##############################
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## two
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T_period = [500000, 500000]
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restarts = [500000]
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restart_weights = [1]
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## four
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T_period = [200000, 100000, 200000]
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restarts = [200000, 300000]
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restart_weights = [.5, .25]
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scheduler = CosineAnnealingLR_Restart(optimizer, T_period, warmup=10000, eta_min=1e-8, restarts=restarts,
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weights=restart_weights)
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'''
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##############################
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# Draw figure
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##############################
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N_iter = 100000
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lr_l = list(range(N_iter))
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for i in range(N_iter):
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scheduler.step()
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current_lr = optimizer.param_groups[0]['lr']
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lr_l[i] = current_lr
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import matplotlib as mpl
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from matplotlib import pyplot as plt
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import matplotlib.ticker as mtick
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mpl.style.use('default')
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import seaborn
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seaborn.set(style='whitegrid')
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seaborn.set_context('paper')
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plt.figure(1)
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plt.subplot(111)
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plt.ticklabel_format(style='sci', axis='x', scilimits=(0, 0))
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plt.title('Title', fontsize=16, color='k')
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plt.plot(list(range(N_iter)), lr_l, linewidth=1.5, label='learning rate scheme')
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legend = plt.legend(loc='upper right', shadow=False)
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ax = plt.gca()
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labels = ax.get_xticks().tolist()
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for k, v in enumerate(labels):
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labels[k] = str(int(v / 1000)) + 'K'
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ax.set_xticklabels(labels)
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ax.yaxis.set_major_formatter(mtick.FormatStrFormatter('%.1e'))
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ax.set_ylabel('Learning rate')
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ax.set_xlabel('Iteration')
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fig = plt.gcf()
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plt.show()
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