Add more algorithms

others/GDAS/lib/scheduler/scheduler.py

@@ -0,0 +1,32 @@
+##################################################
+# Copyright (c) Xuanyi Dong [GitHub D-X-Y], 2019 #
+##################################################
+import torch
+from bisect import bisect_right
+
+
+class MultiStepLR(torch.optim.lr_scheduler._LRScheduler):
+
+  def __init__(self, optimizer, milestones, gammas, last_epoch=-1):
+    if not list(milestones) == sorted(milestones):
+      raise ValueError('Milestones should be a list of'
+                       ' increasing integers. Got {:}', milestones)
+    assert len(milestones) == len(gammas), '{:} vs {:}'.format(milestones, gammas)
+    self.milestones = milestones
+    self.gammas = gammas
+    super(MultiStepLR, self).__init__(optimizer, last_epoch)
+
+  def get_lr(self):
+    LR = 1
+    for x in self.gammas[:bisect_right(self.milestones, self.last_epoch)]: LR = LR * x
+    return [base_lr * LR for base_lr in self.base_lrs]
+
+
+def obtain_scheduler(config, optimizer):
+  if config.type == 'multistep':
+    scheduler = MultiStepLR(optimizer, milestones=config.milestones, gammas=config.gammas)
+  elif config.type == 'cosine':
+    scheduler = torch.optim.lr_scheduler.CosineAnnealingLR(optimizer, config.epochs)
+  else:
+    raise ValueError('Unknown learning rate scheduler type : {:}'.format(config.type))
+  return scheduler