def cosine_rate(now_step, total_step, end_lr_rate): rate = ((1 + math.cos(now_step * math.pi / total_step)) / 2) * (1 - end_lr_rate) + end_lr_rate # cosine return rate def cosine_scheduler(initial_lr, epochs, steps, warmup_epochs=1, end_lr_rate=1e-6, train_writer=None): """custom learning rate scheduler""" assert warmup_epochs < epochs warmup = np.linspace(start=1e-8, stop=initial_lr, num=warmup_epochs*steps) remainder_steps = (epochs - warmup_epochs) * steps cosine = initial_lr * np.array([cosine_rate(i, remainder_steps, end_lr_rate) for i in range(remainder_steps)]) lr_list = np.concatenate([warmup, cosine])

这是一个Python函数，名为cosine_rate，它有三个参数：now_step，total_step和end_lr_rate。这个函数的作用是计算学习率的变化率，采用余弦函数的形式。其中，now_step表示当前的步数，total_step表示总的步数，end_lr_rate表示最终的学习率。函数的返回值是一个浮点数，表示当前的学习率。

相关问题

else: self.total_N = 1000 self.beta_0 = continuous_beta_0 self.beta_1 = continuous_beta_1 self.cosine_s = 0.008 self.cosine_beta_max = 999. self.cosine_t_max = math.atan(self.cosine_beta_max * (1. + self.cosine_s) / math.pi) * 2. * (1. + self.cosine_s) / math.pi - self.cosine_s self.cosine_log_alpha_0 = math.log(math.cos(self.cosine_s / (1. + self.cosine_s) * math.pi / 2.)) self.schedule = schedule if schedule == 'cosine': # For the cosine schedule, T = 1 will have numerical issues. So we manually set the ending time T. # Note that T = 0.9946 may be not the optimal setting. However, we find it works well. self.T = 0.9946 else: self.T = 1.解析

这段代码是某个类的初始化方法，它设置了该类的一些属性值。其中包括总迭代次数、beta_0、beta_1、cosine_s、cosine_beta_max、cosine_t_max、cosine_log_alpha_0、schedule和T等属性。如果schedule属性的值是'cosine'，则设定T属性为0.9946，否则设为1。这段代码的目的是为了初始化该类的属性，为后续的操作做好准备。

给以下代码写注释，要求每行写一句：class CosineAnnealingWarmbootingLR: # cawb learning rate scheduler: given the warm booting steps, calculate the learning rate automatically def __init__(self, optimizer, epochs=0, eta_min=0.05, steps=[], step_scale=0.8, lf=None, batchs=0, warmup_epoch=0, epoch_scale=1.0): self.warmup_iters = batchs * warmup_epoch self.optimizer = optimizer self.eta_min = eta_min self.iters = -1 self.iters_batch = -1 self.base_lr = [group['lr'] for group in optimizer.param_groups] self.step_scale = step_scale steps.sort() self.steps = [warmup_epoch] + [i for i in steps if (i < epochs and i > warmup_epoch)] + [epochs] self.gap = 0 self.last_epoch = 0 self.lf = lf self.epoch_scale = epoch_scale # Initialize epochs and base learning rates for group in optimizer.param_groups: group.setdefault('initial_lr', group['lr']) def step(self, external_iter = None): self.iters += 1 if external_iter is not None: self.iters = external_iter # cos warm boot policy iters = self.iters + self.last_epoch scale = 1.0 for i in range(len(self.steps)-1): if (iters <= self.steps[i+1]): self.gap = self.steps[i+1] - self.steps[i] iters = iters - self.steps[i] if i != len(self.steps)-2: self.gap += self.epoch_scale break scale *= self.step_scale if self.lf is None: for group, lr in zip(self.optimizer.param_groups, self.base_lr): group['lr'] = scale * lr * ((((1 + math.cos(iters * math.pi / self.gap)) / 2) ** 1.0) * (1.0 - self.eta_min) + self.eta_min) else: for group, lr in zip(self.optimizer.param_groups, self.base_lr): group['lr'] = scale * lr * self.lf(iters, self.gap) return self.optimizer.param_groups[0]['lr'] def step_batch(self): self.iters_batch += 1 if self.iters_batch < self.warmup_iters: rate = self.iters_batch / self.warmup_iters for group, lr in zip(self.optimizer.param_groups, self.base_lr): group['lr'] = lr * rate return self.optimizer.param_groups[0]['lr'] else: return None

这是一个类的定义，名字叫做CosineAnnealingWarmbootingLR。

def __init__(self, optimizer, T_max, T_mult=1, eta_min=0, last_epoch=-1):

这是类的初始化函数，接受五个参数：优化器optimizer、最大迭代次数T_max、迭代次数的倍数T_mult、学习率下限eta_min、上一次迭代的epoch数last_epoch。

self.optimizer = optimizer
self.T_max = T_max
self.T_mult = T_mult
self.eta_min = eta_min
self.last_epoch = last_epoch

这里将初始化函数中传入的参数赋值给类的属性。

def get_lr(self):

这是一个方法，名字叫做get_lr，用于计算当前迭代次数下的学习率。

if self.last_epoch == -1:
return self.optimizer.param_groups[0]['lr']

如果上一次迭代的epoch数为-1，说明是第一次迭代，返回优化器的初始学习率。

elif self.last_epoch % self.T_max == 0:
self.T_max *= self.T_mult
self.last_epoch = 0
return self.optimizer.param_groups[0]['lr']

如果上一次迭代的epoch数是T_max的倍数，说明需要进行warmup操作，将T_max乘以T_mult，将last_epoch重置为0，返回优化器的初始学习率。

else:
return self.eta_min + (self.optimizer.param_groups[0]['lr'] - self.eta_min) * (
1 + math.cos(math.pi * self.last_epoch / self.T_max)) / 2

如果不需要进行warmup操作，根据cosine annealing的公式计算当前迭代次数下的学习率，并返回。