diff --git a/scheduler/tanh_lr.py b/scheduler/tanh_lr.py new file mode 100644 index 00000000..a8a67777 --- /dev/null +++ b/scheduler/tanh_lr.py @@ -0,0 +1,81 @@ +import logging +import math +import numpy as np +import torch + +from .scheduler import Scheduler + + +logger = logging.getLogger(__name__) + + +class TanhLRScheduler(Scheduler): + """ + Cosine annealing with restarts. + This is described in the paper https://arxiv.org/abs/1608.03983. + """ + + def __init__(self, + optimizer: torch.optim.Optimizer, + t_initial: int, + lb: float = -6., + ub: float = 4., + t_mul: float = 1., + lr_min: float = 0., + decay_rate: float = 1., + warmup_updates=0, + warmup_lr_init=0, + initialize=True) -> None: + super().__init__(optimizer, param_group_field="lr", initialize=initialize) + + assert t_initial > 0 + assert lr_min >= 0 + self.lb = lb + self.ub = ub + self.t_initial = t_initial + self.t_mul = t_mul + self.lr_min = lr_min + self.decay_rate = decay_rate + self.cycle_limit = 0 + self.warmup_updates = warmup_updates + self.warmup_lr_init = warmup_lr_init + if self.warmup_updates: + self.warmup_steps = [(v - warmup_lr_init) / self.warmup_updates for v in self.base_values] + else: + self.warmup_steps = [1 for _ in self.base_values] + if self.warmup_lr_init: + super().update_groups(self.warmup_lr_init) + + def get_epoch_values(self, epoch: int): + # this scheduler doesn't update on epoch + return None + + def get_update_values(self, num_updates: int): + if num_updates < self.warmup_updates: + lrs = [self.warmup_lr_init + num_updates * s for s in self.warmup_steps] + else: + curr_updates = num_updates - self.warmup_updates + + if self.t_mul != 1: + i = math.floor(math.log(1 - curr_updates / self.t_initial * (1 - self.t_mul), self.t_mul)) + t_i = self.t_mul ** i * self.t_initial + t_curr = curr_updates - (1 - self.t_mul ** i) / (1 - self.t_mul) * self.t_initial + else: + i = curr_updates // self.t_initial + t_i = self.t_initial + t_curr = curr_updates - (self.t_initial * i) + + if self.cycle_limit == 0 or i <= self.cycle_limit: + gamma = self.decay_rate ** i + lr_min = self.lr_min * gamma + lr_max_values = [v * gamma for v in self.base_values] + + tr = t_curr / t_i + lrs = [ + lr_min + 0.5 * (lr_max - lr_min) * (1 - math.tanh(self.lb * (1. - tr) + self.ub * tr)) + for lr_max in lr_max_values + ] + else: + lrs = [self.lr_min * (self.decay_rate ** self.cycle_limit) for _ in self.base_values] + + return lrs