import collections import inspect import logging as log import os import warnings from abc import ABC, abstractmethod from argparse import Namespace from typing import Any, Callable, Dict, List, Optional, Tuple, Union import torch from torch import Tensor import torch.distributed as torch_distrib from torch.nn.parallel import DistributedDataParallel from torch.optim import Adam from torch.optim.optimizer import Optimizer from torch.utils.data import DataLoader from pytorch_lightning.core.grads import GradInformation from pytorch_lightning.core.hooks import ModelHooks from pytorch_lightning.core.memory import ModelSummary from pytorch_lightning.core.saving import ModelIO, load_hparams_from_tags_csv from pytorch_lightning.overrides.data_parallel import LightningDistributedDataParallel from pytorch_lightning.utilities.debugging import MisconfigurationException try: import torch_xla.core.xla_model as xm except ImportError: XLA_AVAILABLE = False else: XLA_AVAILABLE = True class LightningModule(ABC, GradInformation, ModelIO, ModelHooks): def __init__(self, *args, **kwargs): super(LightningModule, self).__init__(*args, **kwargs) #: Current dtype self.dtype = torch.FloatTensor self.exp_save_path = None #: The current epoch self.current_epoch = 0 #: Total training batches seen across all epochs self.global_step = 0 self.loaded_optimizer_states_dict = {} #: Pointer to the trainer object self.trainer = None #: Pointer to the logger object self.logger = None self.example_input_array = None #: True if your model is currently running on GPUs. #: Useful to set flags around the LightningModule for different CPU vs GPU behavior. self.on_gpu = False #: True if using dp self.use_dp = False #: True if using ddp self.use_ddp = False #: True if using ddp2 self.use_ddp2 = False #: True if using amp self.use_amp = False self.hparams = None def print(self, *args, **kwargs) -> None: r""" Prints only from process 0. Use this in any distributed mode to log only once Args: x (object): The thing to print Examples: .. code-block:: python # example if we were using this model as a feature extractor def forward(self, x): self.print(x, 'in loader') """ if self.trainer.proc_rank == 0: print(*args, **kwargs) @abstractmethod def forward(self, *args, **kwargs): r""" Same as torch.nn.Module.forward(), however in Lightning you want this to define the operations you want to use for prediction (ie: on a server or as a feature extractor). Normally you'd call self.forward() from your training_step() method. This makes it easy to write a complex system for training with the outputs you'd want in a prediction setting. Args: x (tensor): Whatever you decide to define in the forward method Return: Predicted output Examples: .. code-block:: python # example if we were using this model as a feature extractor def forward(self, x): feature_maps = self.convnet(x) return feature_maps def training_step(self, batch, batch_idx): x, y = batch feature_maps = self.forward(x) logits = self.classifier(feature_maps) # ... return loss # splitting it this way allows model to be used a feature extractor model = MyModelAbove() inputs = server.get_request() results = model(inputs) server.write_results(results) # ------------- # This is in stark contrast to torch.nn.Module where normally you would have this: def forward(self, batch): x, y = batch feature_maps = self.convnet(x) logits = self.classifier(feature_maps) return logits """ def training_step(self, *args, **kwargs) -> Union[ int, Dict[str, Union[Tensor, Dict[str, Tensor]]] ]: r"""return loss, dict with metrics for tqdm Args: batch (torch.nn.Tensor | (Tensor, Tensor) | [Tensor, Tensor]): The output of your dataloader. A tensor, tuple or list batch_idx (int): Integer displaying index of this batch optimizer_idx (int): If using multiple optimizers, this argument will also be present. hiddens(:`Tensor `_): Passed in if truncated_bptt_steps > 0. Return: dict with loss key and optional log, progress keys if implementing training_step, return whatever you need in that step: - loss -> tensor scalar [REQUIRED] - progress_bar -> Dict for progress bar display. Must have only tensors - log -> Dict of metrics to add to logger. Must have only tensors (no images, etc) In this step you'd normally do the forward pass and calculate the loss for a batch. You can also do fancier things like multiple forward passes or something model specific. Examples: .. code-block:: python def training_step(self, batch, batch_idx): x, y, z = batch # implement your own out = self.forward(x) loss = self.loss(out, x) logger_logs = {'training_loss': loss} # optional (MUST ALL BE TENSORS) # if using TestTubeLogger or TensorBoardLogger you can nest scalars logger_logs = {'losses': logger_logs} # optional (MUST ALL BE TENSORS) output = { 'loss': loss, # required 'progress_bar': {'training_loss': loss}, # optional (MUST ALL BE TENSORS) 'log': logger_logs } # return a dict return output If you define multiple optimizers, this step will be called with an additional `optimizer_idx` param. .. code-block:: python # Multiple optimizers (ie: GANs) def training_step(self, batch, batch_idx, optimizer_idx): if optimizer_idx == 0: # do training_step with encoder if optimizer_idx == 1: # do training_step with decoder If you add truncated back propagation through time you will also get an additional argument with the hidden states of the previous step. .. code-block:: python # Truncated back-propagation through time def training_step(self, batch, batch_idx, hiddens): # hiddens are the hiddens from the previous truncated backprop step ... out, hiddens = self.lstm(data, hiddens) ... return { "loss": ..., "hiddens": hiddens # remember to detach() this } You can also return a -1 instead of a dict to stop the current loop. This is useful if you want to break out of the current training epoch early. """ def training_end(self, *args, **kwargs): """ Warnings: Deprecated in v0.7.0. use training_step_end instead """ def training_step_end(self, *args, **kwargs) -> Dict[ str, Union[Tensor, Dict[str, Tensor]] ]: """ Use this when training with dp or ddp2 because training_step will operate on only part of the batch. However, this is still optional and only needed for things like softmax or NCE loss. .. note:: If you later switch to ddp or some other mode, this will still be called so that you don't have to change your code .. code-block:: python # pseudocode sub_batches = split_batches_for_dp(batch) batch_parts_outputs = [training_step(sub_batch) for sub_batch in sub_batches] training_step_end(batch_parts_outputs) Args: batch_parts_outputs: What you return in `training_step` for each batch part. Return: dictionary with loss key and optional log, progress keys: - loss -> tensor scalar [REQUIRED] - progress_bar -> Dict for progress bar display. Must have only tensors - log -> Dict of metrics to add to logger. Must have only tensors (no images, etc) In this case you should define training_step_end to perform those calculations. Examples: .. code-block:: python # WITHOUT training_step_end # if used in DP or DDP2, this batch is 1/num_gpus large def training_step(self, batch, batch_idx): # batch is 1/num_gpus big x, y = batch out = self.forward(x) loss = self.softmax(out) loss = nce_loss(loss) return {'loss': loss} # -------------- # with training_step_end to do softmax over the full batch def training_step(self, batch, batch_idx): # batch is 1/num_gpus big x, y = batch out = self.forward(x) return {'out': out} def training_step_end(self, outputs): # this out is now the full size of the batch out = outputs['out'] # this softmax now uses the full batch size loss = nce_loss(loss) return {'loss': loss} .. seealso:: see the `multi-gpu guide for more details `_. """ def validation_step(self, *args, **kwargs) -> Dict[str, Tensor]: r""" Operate on a single batch of data from the validation set In this step you'd might generate examples or calculate anything of interest like accuracy. .. code-block:: python # the pseudocode for these calls val_outs = [] for val_batch in val_data: out = validation_step(train_batch) val_outs.append(out validation_epoch_end(val_outs) Args: batch (torch.nn.Tensor | (Tensor, Tensor) | [Tensor, Tensor]): The output of your dataloader. A tensor, tuple or list batch_idx (int): The index of this batch dataloader_idx (int): The index of the dataloader that produced this batch (only if multiple val datasets used) Return: Dict or OrderedDict - passed to validation_epoch_end. If you defined validation_step_end it will go to that first. .. code-block:: python # pseudocode of order out = validation_step() if defined('validation_step_end'): out = validation_step_end(out) out = validation_epoch_end(out) .. code-block:: python # if you have one val dataloader: def validation_step(self, batch, batch_idx) # if you have multiple val dataloaders: def validation_step(self, batch, batch_idx, dataloader_idx) Examples: .. code-block:: python # CASE 1: A single validation dataset def validation_step(self, batch, batch_idx): x, y = batch # implement your own out = self.forward(x) loss = self.loss(out, y) # log 6 example images # or generated text... or whatever sample_imgs = x[:6] grid = torchvision.utils.make_grid(sample_imgs) self.logger.experiment.add_image('example_images', grid, 0) # calculate acc labels_hat = torch.argmax(out, dim=1) val_acc = torch.sum(y == labels_hat).item() / (len(y) * 1.0) # all optional... # return whatever you need for the collation function validation_end output = OrderedDict({ 'val_loss': loss_val, 'val_acc': torch.tensor(val_acc), # everything must be a tensor }) # return an optional dict return output If you pass in multiple val datasets, validation_step will have an additional argument. .. code-block:: python # CASE 2: multiple validation datasets def validation_step(self, batch, batch_idx, dataset_idx): # dataset_idx tells you which dataset this is. .. note:: If you don't need to validate you don't need to implement this method. .. note:: When the validation_step is called, the model has been put in eval mode and PyTorch gradients have been disabled. At the end of validation, the model goes back to training mode and gradients are enabled. """ def validation_step_end(self, *args, **kwargs) -> Dict[str, Tensor]: """ Use this when validating with dp or ddp2 because validation_step will operate on only part of the batch. However, this is still optional and only needed for things like softmax or NCE loss. .. note:: If you later switch to ddp or some other mode, this will still be called so that you don't have to change your code .. code-block:: python # pseudocode sub_batches = split_batches_for_dp(batch) batch_parts_outputs = [validation_step(sub_batch) for sub_batch in sub_batches] validation_step_end(batch_parts_outputs) Args: batch_parts_outputs: What you return in `validation_step` for each batch part. Return: Dict or OrderedDict - passed to the validation_epoch_end In this case you should define validation_step_end to perform those calculations. Examples: .. code-block:: python # WITHOUT validation_step_end # if used in DP or DDP2, this batch is 1/num_gpus large def validation_step(self, batch, batch_idx): # batch is 1/num_gpus big x, y = batch out = self.forward(x) loss = self.softmax(out) loss = nce_loss(loss) return {'loss': loss} # -------------- # with validation_step_end to do softmax over the full batch def validation_step(self, batch, batch_idx): # batch is 1/num_gpus big x, y = batch out = self.forward(x) return {'out': out} def validation_epoch_end(self, outputs): # this out is now the full size of the batch out = outputs['out'] # this softmax now uses the full batch size loss = nce_loss(loss) return {'loss': loss} .. seealso:: see the `multi-gpu guide for more details `_. """ def validation_end(self, outputs): """ Warnings: Deprecated in v0.7.0. use validation_epoch_end instead. Will be removed 1.0.0 """ def validation_epoch_end( self, outputs: Union[List[Dict[str, Tensor]], List[List[Dict[str, Tensor]]]] ) -> Dict[str, Dict[str, Tensor]]: """ Called at end of validation epoch with the output of all validation_steps .. code-block:: python # the pseudocode for these calls val_outs = [] for val_batch in val_data: out = validation_step(train_batch) train_outs.append(out) validation_epoch_end(val_outs) Args: outputs: List of outputs you defined in validation_step, or if there are multiple dataloaders, a list containing a list of outputs for each dataloader Return: Dict or OrderedDict (dict): Dict has the following optional keys: progress_bar -> Dict for progress bar display. Must have only tensors log -> Dict of metrics to add to logger. Must have only tensors (no images, etc) .. note:: If you didn't define a validation_step, this won't be called. - The outputs here are strictly for logging or progress bar. - If you don't need to display anything, don't return anything. - If you want to manually set current step, you can specify the 'step' key in the 'log' Dict Examples: With a single dataloader .. code-block:: python def validation_epoch_end(self, outputs): val_acc_mean = 0 for output in outputs: val_acc_mean += output['val_acc'] val_acc_mean /= len(outputs) tqdm_dict = {'val_acc': val_acc_mean.item()} # show val_loss and val_acc in progress bar but only log val_loss results = { 'progress_bar': tqdm_dict, 'log': {'val_acc': val_acc_mean.item()} } return results With multiple dataloaders, `outputs` will be a list of lists. The outer list contains one entry per dataloader, while the inner list contains the individual outputs of each validation step for that dataloader. .. code-block:: python def validation_epoch_end(self, outputs): val_acc_mean = 0 i = 0 for dataloader_outputs in outputs: for output in dataloader_outputs: val_acc_mean += output['val_acc'] i += 1 val_acc_mean /= i tqdm_dict = {'val_acc': val_acc_mean.item()} # show val_loss and val_acc in progress bar but only log val_loss results = { 'progress_bar': tqdm_dict, 'log': {'val_acc': val_acc_mean.item(), 'step': self.current_epoch} } return results """ def test_step(self, *args, **kwargs) -> Dict[str, Tensor]: r""" Operate on a single batch of data from the test set In this step you'd normally generate examples or calculate anything of interest such as accuracy. .. code-block:: python # the pseudocode for these calls test_outs = [] for test_batch in test_data: out = test_step(train_batch) test_outs.append(out) test_epoch_end(test_outs) Args: batch (torch.nn.Tensor | (Tensor, Tensor) | [Tensor, Tensor]): The output of your dataloader. A tensor, tuple or list batch_idx (int): The index of this batch dataloader_idx (int): The index of the dataloader that produced this batch (only if multiple test datasets used) Return: Dict or OrderedDict - passed to the test_step_end .. code-block:: python # if you have one test dataloader: def test_step(self, batch, batch_idx) # if you have multiple test dataloaders: def test_step(self, batch, batch_idx, dataloader_idx) Examples: .. code-block:: python # CASE 1: A single test dataset def test_step(self, batch, batch_idx): x, y = batch # implement your own out = self.forward(x) loss = self.loss(out, y) # log 6 example images # or generated text... or whatever sample_imgs = x[:6] grid = torchvision.utils.make_grid(sample_imgs) self.logger.experiment.add_image('example_images', grid, 0) # calculate acc labels_hat = torch.argmax(out, dim=1) val_acc = torch.sum(y == labels_hat).item() / (len(y) * 1.0) # all optional... # return whatever you need for the collation function validation_end output = OrderedDict({ 'val_loss': loss_val, 'val_acc': torch.tensor(val_acc), # everything must be a tensor }) # return an optional dict return output If you pass in multiple validation datasets, validation_step will have an additional argument. .. code-block:: python # CASE 2: multiple validation datasets def test_step(self, batch, batch_idx, dataset_idx): # dataset_idx tells you which dataset this is. .. note:: If you don't need to validate you don't need to implement this method. .. note:: When the test_step is called, the model has been put in eval mode and PyTorch gradients have been disabled. At the end of the test epoch, the model goes back to training mode and gradients are enabled. """ def test_step_end(self, *args, **kwargs) -> Dict[str, Tensor]: """ Use this when testing with dp or ddp2 because test_step will operate on only part of the batch. However, this is still optional and only needed for things like softmax or NCE loss. .. note:: If you later switch to ddp or some other mode, this will still be called so that you don't have to change your code .. code-block:: python # pseudocode sub_batches = split_batches_for_dp(batch) batch_parts_outputs = [test_step(sub_batch) for sub_batch in sub_batches] test_step_end(batch_parts_outputs) Args: batch_parts_outputs: What you return in `training_step` for each batch part. Return: Dict or OrderedDict - passed to the test_epoch_end In this case you should define test_step_end to perform those calculations. Examples: .. code-block:: python # WITHOUT test_step_end # if used in DP or DDP2, this batch is 1/num_gpus large def test_step(self, batch, batch_idx): # batch is 1/num_gpus big x, y = batch out = self.forward(x) loss = self.softmax(out) loss = nce_loss(loss) return {'loss': loss} # -------------- # with test_step_end to do softmax over the full batch def test_step(self, batch, batch_idx): # batch is 1/num_gpus big x, y = batch out = self.forward(x) return {'out': out} def test_step_end(self, outputs): # this out is now the full size of the batch out = outputs['out'] # this softmax now uses the full batch size loss = nce_loss(loss) return {'loss': loss} .. seealso:: see the `multi-gpu guide for more details `_. """ def test_end(self, outputs): """ Warnings: Deprecated in v0.7.0. use test_epoch_end instead. Will be removed 1.0.0 """ def test_epoch_end( self, outputs: Union[List[Dict[str, Tensor]], List[List[Dict[str, Tensor]]]] ) -> Dict[str, Dict[str, Tensor]]: """ Called at end of test epoch with the output of all test_steps. .. code-block:: python # the pseudocode for these calls test_outs = [] for test_batch in test_data: out = test_step(test_batch) test_outs.append(out) test_epoch_end(test_outs) Args: outputs: List of outputs you defined in test_step, or if there are multiple dataloaders, a list containing a list of outputs for each dataloader Return: Dict or OrderedDict (dict): Dict has the following optional keys: progress_bar -> Dict for progress bar display. Must have only tensors log -> Dict of metrics to add to logger. Must have only tensors (no images, etc) .. note:: If you didn't define a test_step, this won't be called. - The outputs here are strictly for logging or progress bar. - If you don't need to display anything, don't return anything. - If you want to manually set current step, specify it with the 'step' key in the 'log' Dict Examples: With a single dataloader .. code-block:: python def test_epoch_end(self, outputs): test_acc_mean = 0 for output in outputs: test_acc_mean += output['test_acc'] test_acc_mean /= len(outputs) tqdm_dict = {'test_acc': test_acc_mean.item()} # show test_loss and test_acc in progress bar but only log test_loss results = { 'progress_bar': tqdm_dict, 'log': {'test_acc': test_acc_mean.item()} } return results With multiple dataloaders, `outputs` will be a list of lists. The outer list contains one entry per dataloader, while the inner list contains the individual outputs of each test step for that dataloader. .. code-block:: python def test_epoch_end(self, outputs): test_acc_mean = 0 i = 0 for dataloader_outputs in outputs: for output in dataloader_outputs: test_acc_mean += output['test_acc'] i += 1 test_acc_mean /= i tqdm_dict = {'test_acc': test_acc_mean.item()} # show test_loss and test_acc in progress bar but only log test_loss results = { 'progress_bar': tqdm_dict, 'log': {'test_acc': test_acc_mean.item(), 'step': self.current_epoch} } return results """ def configure_ddp( self, model: 'LightningModule', device_ids: List[int] ) -> DistributedDataParallel: r""" Override to init DDP in your own way or with your own wrapper. The only requirements are that: 1. On a validation batch the call goes to model.validation_step. 2. On a training batch the call goes to model.training_step. 3. On a testing batch, the call goes to model.test_step Args: model: the LightningModule currently being optimized device_ids: the list of GPU ids Return: DDP wrapped model Examples: .. code-block:: python # default implementation used in Trainer def configure_ddp(self, model, device_ids): # Lightning DDP simply routes to test_step, val_step, etc... model = LightningDistributedDataParallel( model, device_ids=device_ids, find_unused_parameters=True ) return model """ model = LightningDistributedDataParallel( model, device_ids=device_ids, find_unused_parameters=True ) return model def init_ddp_connection(self, proc_rank: int, world_size: int) -> None: r""" Override to define your custom way of setting up a distributed environment. Lightning's implementation uses env:// init by default and sets the first node as root. Args: proc_rank: The current process rank within the node. world_size: Number of GPUs being use across all nodes. (num_nodes*nb_gpu_nodes). Examples: .. code-block:: python def init_ddp_connection(self): # use slurm job id for the port number # guarantees unique ports across jobs from same grid search try: # use the last 4 numbers in the job id as the id default_port = os.environ['SLURM_JOB_ID'] default_port = default_port[-4:] # all ports should be in the 10k+ range default_port = int(default_port) + 15000 except Exception as e: default_port = 12910 # if user gave a port number, use that one instead try: default_port = os.environ['MASTER_PORT'] except Exception: os.environ['MASTER_PORT'] = str(default_port) # figure out the root node addr try: root_node = os.environ['SLURM_NODELIST'].split(' ')[0] except Exception: root_node = '127.0.0.2' root_node = self.trainer.resolve_root_node_address(root_node) os.environ['MASTER_ADDR'] = root_node dist.init_process_group( 'nccl', rank=self.proc_rank, world_size=self.world_size ) """ # use slurm job id for the port number # guarantees unique ports across jobs from same grid search try: # use the last 4 numbers in the job id as the id default_port = os.environ['SLURM_JOB_ID'] default_port = default_port[-4:] # all ports should be in the 10k+ range default_port = int(default_port) + 15000 except Exception: default_port = 12910 # if user gave a port number, use that one instead try: default_port = os.environ['MASTER_PORT'] except Exception: os.environ['MASTER_PORT'] = str(default_port) # figure out the root node addr try: root_node = os.environ['SLURM_NODELIST'].split(' ')[0] except Exception: root_node = '127.0.0.2' root_node = self.trainer.resolve_root_node_address(root_node) os.environ['MASTER_ADDR'] = root_node torch_distrib.init_process_group('nccl', rank=proc_rank, world_size=world_size) def configure_apex( self, amp: object, model: 'LightningModule', optimizers: List[Optimizer], amp_level: str ) -> Tuple['LightningModule', List[Optimizer]]: r""" Override to init AMP your own way Must return a model and list of optimizers Args: amp: pointer to amp library object model: pointer to current lightningModule optimizers: list of optimizers passed in configure_optimizers() amp_level: AMP mode chosen ('O1', 'O2', etc...) Return: Apex wrapped model and optimizers Examples: .. code-block:: python # Default implementation used by Trainer. def configure_apex(self, amp, model, optimizers, amp_level): model, optimizers = amp.initialize( model, optimizers, opt_level=amp_level, ) return model, optimizers """ model, optimizers = amp.initialize( model, optimizers, opt_level=amp_level, ) return model, optimizers def configure_optimizers(self) -> Union[ Optimizer, List[Optimizer], Tuple[Optimizer, ...], Tuple[List[Optimizer], List] ]: r""" Choose what optimizers and learning-rate schedulers to use in your optimization. Normally you'd need one. But in the case of GANs or similar you might have multiple. If you don't define this method Lightning will automatically use Adam(lr=1e-3) Return: any of these 3 options: - Single optimizer - List or Tuple - List of optimizers - Two lists - The first list has multiple optimizers, the second a list of LR schedulers Examples: .. code-block:: python # most cases (default if not defined) def configure_optimizers(self): opt = Adam(self.parameters(), lr=1e-3) return opt # multiple optimizer case (eg: GAN) def configure_optimizers(self): generator_opt = Adam(self.model_gen.parameters(), lr=0.01) disriminator_opt = Adam(self.model_disc.parameters(), lr=0.02) return generator_opt, disriminator_opt # example with learning_rate schedulers def configure_optimizers(self): generator_opt = Adam(self.model_gen.parameters(), lr=0.01) disriminator_opt = Adam(self.model_disc.parameters(), lr=0.02) discriminator_sched = CosineAnnealing(discriminator_opt, T_max=10) return [generator_opt, disriminator_opt], [discriminator_sched] # example with step-based learning_rate schedulers def configure_optimizers(self): gen_opt = Adam(self.model_gen.parameters(), lr=0.01) dis_opt = Adam(self.model_disc.parameters(), lr=0.02) gen_sched = {'scheduler': ExponentialLR(gen_opt, 0.99), 'interval': 'step'} # called after each training step dis_sched = CosineAnnealing(discriminator_opt, T_max=10) # called every epoch return [gen_opt, dis_opt], [gen_sched, dis_sched] Some things to know - Lightning calls ``.backward()`` and ``.step()`` on each optimizer and learning rate scheduler as needed. - If you use 16-bit precision (``precision=16``), Lightning will automatically handle the optimizers for you. - If you use multiple optimizers, training_step will have an additional ``optimizer_idx`` parameter. - If you use LBFGS lightning handles the closure function automatically for you - If you use multiple optimizers, gradients will be calculated only for the parameters of current optimizer at each training step. - If you need to control how often those optimizers step or override the default .step() schedule, override the `optimizer_step` hook. - If you only want to call a learning rate scheduler every `x` step or epoch, you can input this as 'frequency' key: dict(scheduler=lr_scheduler, interval='step' or 'epoch', frequency=x) """ return Adam(self.parameters(), lr=1e-3) def optimizer_step( self, epoch: int, batch_idx: int, optimizer: Optimizer, optimizer_idx: int, second_order_closure: Optional[Callable] = None, ) -> None: r""" Override this method to adjust the default way the Trainer calls each optimizer. By default, Lightning calls .step() and zero_grad() as shown in the example once per optimizer. Args: epoch: Current epoch batch_idx: Index of current batch optimizer: A PyTorch optimizer optimizer_idx: If you used multiple optimizers this indexes into that list second_order_closure: closure for second order methods Examples: .. code-block:: python # DEFAULT def optimizer_step(self, current_epoch, batch_idx, optimizer, optimizer_idx, second_order_closure=None): optimizer.step() optimizer.zero_grad() # Alternating schedule for optimizer steps (ie: GANs) def optimizer_step(self, current_epoch, batch_idx, optimizer, optimizer_idx, second_order_closure=None): # update generator opt every 2 steps if optimizer_idx == 0: if batch_idx % 2 == 0 : optimizer.step() optimizer.zero_grad() # update discriminator opt every 4 steps if optimizer_idx == 1: if batch_idx % 4 == 0 : optimizer.step() optimizer.zero_grad() # ... # add as many optimizers as you want Here's another example showing how to use this for more advanced things such as learning-rate warm-up: .. code-block:: python # learning rate warm-up def optimizer_step(self, current_epoch, batch_idx, optimizer, optimizer_idx, second_order_closure=None): # warm up lr if self.trainer.global_step < 500: lr_scale = min(1., float(self.trainer.global_step + 1) / 500.) for pg in optimizer.param_groups: pg['lr'] = lr_scale * self.hparams.learning_rate # update params optimizer.step() optimizer.zero_grad() """ if self.trainer.use_tpu and XLA_AVAILABLE: xm.optimizer_step(optimizer) elif isinstance(optimizer, torch.optim.LBFGS): optimizer.step(second_order_closure) else: optimizer.step() # clear gradients optimizer.zero_grad() def tbptt_split_batch(self, batch: Tensor, split_size: int) -> list: r""" When using truncated backpropagation through time, each batch must be split along the time dimension. Lightning handles this by default, but for custom behavior override this function. Args: batch: Current batch split_size: How big the split is Return: list of batch splits. Each split will be passed to forward_step to enable truncated back propagation through time. The default implementation splits root level Tensors and Sequences at dim=1 (i.e. time dim). It assumes that each time dim is the same length. Examples: .. code-block:: python def tbptt_split_batch(self, batch, split_size): splits = [] for t in range(0, time_dims[0], split_size): batch_split = [] for i, x in enumerate(batch): if isinstance(x, torch.Tensor): split_x = x[:, t:t + split_size] elif isinstance(x, collections.Sequence): split_x = [None] * len(x) for batch_idx in range(len(x)): split_x[batch_idx] = x[batch_idx][t:t + split_size] batch_split.append(split_x) splits.append(batch_split) return splits .. note:: Called in the training loop after on_batch_start if ``truncated_bptt_steps > 0``. Each returned batch split is passed separately to ``training_step(...)``. """ time_dims = [len(x[0]) for x in batch if isinstance(x, (torch.Tensor, collections.Sequence))] assert len(time_dims) >= 1, "Unable to determine batch time dimension" assert all(x == time_dims[0] for x in time_dims), "Batch time dimension length is ambiguous" splits = [] for t in range(0, time_dims[0], split_size): batch_split = [] for i, x in enumerate(batch): if isinstance(x, torch.Tensor): split_x = x[:, t:t + split_size] elif isinstance(x, collections.Sequence): split_x = [None] * len(x) for batch_idx in range(len(x)): split_x[batch_idx] = x[batch_idx][t:t + split_size] batch_split.append(split_x) splits.append(batch_split) return splits def prepare_data(self) -> None: """Use this to download and prepare data. In distributed (GPU, TPU), this will only be called once Return: PyTorch DataLoader This is called before requesting the dataloaders .. code-block:: python model.prepare_data() model.train_dataloader() model.val_dataloader() model.test_dataloader() Examples: .. code-block:: python def prepare_data(self): download_imagenet() clean_imagenet() cache_imagenet() """ def train_dataloader(self) -> DataLoader: """Implement a PyTorch DataLoader Return: PyTorch DataLoader Return a dataloader. It will not be called every epoch unless you set ```Trainer(reload_dataloaders_every_epoch=True)```. It's recommended that all data downloads and preparation happen in prepare_data(). .. note:: Lightning adds the correct sampler for distributed and arbitrary hardware. No need to set yourself. - .fit() - ... - prepare_data() - train_dataloader Example: .. code-block:: python def train_dataloader(self): transform = transforms.Compose([transforms.ToTensor(), transforms.Normalize((0.5,), (1.0,))]) dataset = MNIST(root='/path/to/mnist/', train=True, transform=transform, download=True) loader = torch.utils.data.DataLoader( dataset=dataset, batch_size=self.hparams.batch_size, shuffle=True ) return loader """ def tng_dataloader(self): # todo: remove in v1.0.0 """Implement a PyTorch DataLoader. Warnings: Deprecated in v0.5.0. use train_dataloader instead. Will be removed 1.0.0 """ output = self.train_dataloader() warnings.warn("`tng_dataloader` has been renamed to `train_dataloader` since v0.5.0." " and this method will be removed in v1.0.0", DeprecationWarning) return output def test_dataloader(self) -> Union[DataLoader, List[DataLoader]]: r""" Return a dataloader. It will not be called every epoch unless you set ```Trainer(reload_dataloaders_every_epoch=True)```. It's recommended that all data downloads and preparation happen in prepare_data(). - .fit() - ... - prepare_data() - train_dataloader - val_dataloader - test_dataloader .. note:: Lightning adds the correct sampler for distributed and arbitrary hardware. No need to set yourself. Return: Single or multiple PyTorch DataLoader Example: .. code-block:: python def test_dataloader(self): transform = transforms.Compose([transforms.ToTensor(), transforms.Normalize((0.5,), (1.0,))]) dataset = MNIST(root='/path/to/mnist/', train=False, transform=transform, download=True) loader = torch.utils.data.DataLoader( dataset=dataset, batch_size=self.hparams.batch_size, shuffle=True ) return loader .. note:: If you don't need a test dataset and a test_step, you don't need to implement this method. """ def val_dataloader(self) -> Union[DataLoader, List[DataLoader]]: r""" Return a dataloader. It will not be called every epoch unless you set ```Trainer(reload_dataloaders_every_epoch=True)```. It's recommended that all data downloads and preparation happen in prepare_data(). - .fit() - ... - prepare_data() - train_dataloader - val_dataloader .. note:: Lightning adds the correct sampler for distributed and arbitrary hardware No need to set yourself. Return: Single or multiple PyTorch DataLoader Examples: .. code-block:: python def val_dataloader(self): transform = transforms.Compose([transforms.ToTensor(), transforms.Normalize((0.5,), (1.0,))]) dataset = MNIST(root='/path/to/mnist/', train=False, transform=transform, download=True) loader = torch.utils.data.DataLoader( dataset=dataset, batch_size=self.hparams.batch_size, shuffle=True ) return loader # can also return multiple dataloaders def val_dataloader(self): return [loader_a, loader_b, ..., loader_n] .. code-block:: python def val_dataloader(self): transform = transforms.Compose([transforms.ToTensor(), transforms.Normalize((0.5,), (1.0,))]) dataset = MNIST(root='/path/to/mnist/', train=False, transform=transform, download=True) loader = torch.utils.data.DataLoader( dataset=dataset, batch_size=self.hparams.batch_size, shuffle=True ) return loader # can also return multiple dataloaders def val_dataloader(self): return [loader_a, loader_b, ..., loader_n] .. note:: If you don't need a validation dataset and a validation_step, you don't need to implement this method. .. note:: In the case where you return multiple `val_dataloaders`, the `validation_step` will have an argument `dataset_idx` which matches the order here. """ @classmethod def load_from_metrics(cls, weights_path, tags_csv, map_location=None): r""" Warning: Deprecated in version 0.7.0. You should use `load_from_checkpoint` instead. Will be removed in v0.9.0. """ warnings.warn( "`load_from_metrics` method has been unified with `load_from_checkpoint` in v0.7.0." " The deprecated method will be removed in v0.9.0.", DeprecationWarning ) return cls.load_from_checkpoint(weights_path, tags_csv=tags_csv, map_location=map_location) @classmethod def load_from_checkpoint( cls, checkpoint_path: str, map_location: Optional[Union[Dict[str, str], str, torch.device, int, Callable]] = None, tags_csv: Optional[str] = None, ) -> 'LightningModule': r""" Primary way of loading model from a checkpoint. When Lightning saves a checkpoint it stores the hyperparameters in the checkpoint if you initialized your LightningModule with an argument called `hparams` which is a Namespace (output of using argparse to parse command line arguments). Example: .. code-block:: python from argparse import Namespace hparams = Namespace(**{'learning_rate': 0.1}) model = MyModel(hparams) class MyModel(LightningModule): def __init__(self, hparams): self.learning_rate = hparams.learning_rate Args: checkpoint_path: Path to checkpoint. map_location: If your checkpoint saved a GPU model and you now load on CPUs or a different number of GPUs, use this to map to the new setup. The behaviour is the same as in `torch.load `_. tags_csv: Optional path to a .csv file with two columns (key, value) as in this example:: key,value drop_prob,0.2 batch_size,32 You most likely won't need this since Lightning will always save the hyperparameters to the checkpoint. However, if your checkpoint weights don't have the hyperparameters saved, use this method to pass in a .csv file with the hparams you'd like to use. These will be converted into a argparse.Namespace and passed into your LightningModule for use. Return: LightningModule with loaded weights and hyperparameters (if available). Example: .. code-block:: python # load weights without mapping ... MyLightningModule.load_from_checkpoint('path/to/checkpoint.ckpt') # or load weights mapping all weights from GPU 1 to GPU 0 ... map_location = {'cuda:1':'cuda:0'} MyLightningModule.load_from_checkpoint( 'path/to/checkpoint.ckpt', map_location=map_location ) # or load weights and hyperparameters from separate files. MyLightningModule.load_from_checkpoint( 'path/to/checkpoint.ckpt', tags_csv='/path/to/hparams_file.csv' ) # predict pretrained_model.eval() pretrained_model.freeze() y_hat = pretrained_model(x) """ if map_location is not None: checkpoint = torch.load(checkpoint_path, map_location=map_location) else: checkpoint = torch.load(checkpoint_path, map_location=lambda storage, loc: storage) if tags_csv is not None: # add the hparams from csv file to checkpoint hparams = load_hparams_from_tags_csv(tags_csv) hparams.__setattr__('on_gpu', False) checkpoint['hparams'] = vars(hparams) model = cls._load_model_state(checkpoint) return model @classmethod def _load_model_state(cls, checkpoint: Dict[str, Any]) -> 'LightningModule': cls_takes_hparams = 'hparams' in inspect.signature(cls.__init__).parameters ckpt_hparams = checkpoint.get('hparams') if cls_takes_hparams: if ckpt_hparams is not None: is_namespace = checkpoint.get('hparams_type') == 'namespace' hparams = Namespace(**ckpt_hparams) if is_namespace else ckpt_hparams else: warnings.warn( f"Checkpoint does not contain hyperparameters but {cls.__name__}'s __init__ " f"contains argument 'hparams'. Will pass in an empty Namespace instead." " Did you forget to store your model hyperparameters in self.hparams?" ) hparams = Namespace() else: # The user's LightningModule does not define a hparams argument if ckpt_hparams is None: hparams = None else: raise MisconfigurationException( f"Checkpoint contains hyperparameters but {cls.__name__}'s __init__ " f"is missing the argument 'hparams'. Are you loading the correct checkpoint?" ) # load the state_dict on the model automatically model_args = [hparams] if hparams else [] model = cls(*model_args) model.load_state_dict(checkpoint['state_dict']) # give model a chance to load something model.on_load_checkpoint(checkpoint) return model def summarize(self, mode: str) -> None: model_summary = ModelSummary(self, mode=mode) log.info('\n' + model_summary.__str__()) def freeze(self) -> None: r""" Freeze all params for inference Example: .. code-block:: python model = MyLightningModule(...) model.freeze() """ for param in self.parameters(): param.requires_grad = False self.eval() def unfreeze(self) -> None: """Unfreeze all params for training. .. code-block:: python model = MyLightningModule(...) model.unfreeze() """ for param in self.parameters(): param.requires_grad = True self.train() def on_load_checkpoint(self, checkpoint: Dict[str, Any]) -> None: r""" Called by lightning to restore your model. If you saved something with **on_save_checkpoint** this is your chance to restore this. Args: checkpoint: Loaded checkpoint Example: .. code-block:: python def on_load_checkpoint(self, checkpoint): # 99% of the time you don't need to implement this method self.something_cool_i_want_to_save = checkpoint['something_cool_i_want_to_save'] .. note:: Lighting auto-restores global step, epoch, and train state including amp scaling. No need for you to restore anything regarding training. """ def on_save_checkpoint(self, checkpoint: Dict[str, Any]) -> None: r""" Called by lightning when saving a checkpoint to give you a chance to store anything else you might want to save Args: checkpoint: Checkpoint to be saved Example: .. code-block:: python def on_save_checkpoint(self, checkpoint): # 99% of use cases you don't need to implement this method checkpoint['something_cool_i_want_to_save'] = my_cool_pickable_object .. note:: Lighting saves all aspects of training (epoch, global step, etc...) including amp scaling. No need for you to store anything about training. """ def get_tqdm_dict(self) -> Dict[str, Union[int, str]]: r""" Additional items to be displayed in the progress bar. Return: Dictionary with the items to be displayed in the progress bar. """ tqdm_dict = { 'loss': '{:.3f}'.format(self.trainer.avg_loss) } if self.trainer.truncated_bptt_steps is not None: tqdm_dict['split_idx'] = self.trainer.split_idx if self.trainer.logger is not None and self.trainer.logger.version is not None: tqdm_dict['v_num'] = self.trainer.logger.version return tqdm_dict