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ReduceLR

class mmedit.engine.schedulers.ReduceLR(optimizer, mode: str = 'min', factor: float = 0.1, patience: int = 10, threshold: float = 0.0001, threshold_mode: str = 'rel', cooldown: int = 0, min_lr: float = 0.0, eps: float = 1e-08, **kwargs)[source]

Decays the learning rate of each parameter group by linearly changing small multiplicative factor until the number of epoch reaches a pre-defined milestone: end.

Notice that such decay can happen simultaneously with other changes to the learning rate from outside this scheduler.

Note

The learning rate of each parameter group will be update at regular

intervals.

Parameters
  • optimizer (Optimizer or OptimWrapper) – Wrapped optimizer.

  • mode (str, optional) – One of min, max. In min mode, lr will be reduced when the quantity monitored has stopped decreasing; in max mode it will be reduced when the quantity monitored has stopped increasing. Default: ‘min’.

  • factor (float, optional) – Factor by which the learning rate will be reduced. new_lr = lr * factor. Default: 0.1.

  • patience (int, optional) – Number of epochs with no improvement after which learning rate will be reduced. For example, if patience = 2, then we will ignore the first 2 epochs with no improvement, and will only decrease the LR after the 3rd epoch if the loss still hasn’t improved then. Default: 10.

  • threshold (float, optional) – Threshold for measuring the new optimum, to only focus on significant changes. Default: 1e-4.

  • threshold_mode (str, optional) – One of rel, abs. In rel mode, dynamic_threshold = best * ( 1 + threshold ) in ‘max’ mode or best * ( 1 - threshold ) in min mode. In abs mode, dynamic_threshold = best + threshold in max mode or best - threshold in min mode. Default: ‘rel’.

  • cooldown (int, optional) – Number of epochs to wait before resuming normal operation after lr has been reduced. Default: 0.

  • min_lr (float, optional) – Minimum LR value to keep. If LR after decay is lower than min_lr, it will be clipped to this value. Default: 0.

  • eps (float, optional) – Minimal decay applied to lr. If the difference between new and old lr is smaller than eps, the update is ignored. Default: 1e-8.

  • begin (int) – Step at which to start updating the learning rate. Defaults to 0.

  • end (int) – Step at which to stop updating the learning rate.

  • last_step (int) – The index of last step. Used for resume without state dict. Defaults to -1.

  • by_epoch (bool) – Whether the scheduled learning rate is updated by epochs. Defaults to True.

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