pytorch-lightning/pytorch_lightning/trainer/trainer.py

import os
import sys
import warnings
import logging as log
from typing import Union, Optional, List, Dict, Tuple

import torch
import torch.distributed as dist
import torch.multiprocessing as mp
from torch.utils.data import DataLoader
from tqdm.auto import tqdm
from torch.optim.optimizer import Optimizer

from pytorch_lightning.callbacks import ModelCheckpoint, EarlyStopping
from pytorch_lightning.loggers import LightningLoggerBase
from pytorch_lightning.profiler.profiler import BaseProfiler
from pytorch_lightning.trainer.auto_mix_precision import TrainerAMPMixin
from pytorch_lightning.trainer.callback_config import TrainerCallbackConfigMixin
from pytorch_lightning.trainer.data_loading import TrainerDataLoadingMixin
from pytorch_lightning.trainer.distrib_data_parallel import TrainerDDPMixin
from pytorch_lightning.trainer.distrib_parts import (
    TrainerDPMixin,
    parse_gpu_ids,
    determine_root_gpu_device
)
from pytorch_lightning.core.lightning import LightningModule
from pytorch_lightning.trainer.evaluation_loop import TrainerEvaluationLoopMixin
from pytorch_lightning.trainer.logging import TrainerLoggingMixin
from pytorch_lightning.trainer.model_hooks import TrainerModelHooksMixin
from pytorch_lightning.trainer.training_io import TrainerIOMixin
from pytorch_lightning.trainer.training_loop import TrainerTrainLoopMixin
from pytorch_lightning.trainer.training_tricks import TrainerTrainingTricksMixin
from pytorch_lightning.utilities.debugging import MisconfigurationException
from pytorch_lightning.profiler import Profiler, PassThroughProfiler


try:
    from apex import amp

    APEX_AVAILABLE = True
except ImportError:
    APEX_AVAILABLE = False

try:
    import torch_xla
    import torch_xla.core.xla_model as xm
    import torch_xla.distributed.xla_multiprocessing as xmp

    XLA_AVAILABLE = True
except ImportError:
    XLA_AVAILABLE = False


class Trainer(TrainerIOMixin,
              TrainerDPMixin,
              TrainerDDPMixin,
              TrainerLoggingMixin,
              TrainerModelHooksMixin,
              TrainerTrainingTricksMixin,
              TrainerDataLoadingMixin,
              TrainerAMPMixin,
              TrainerEvaluationLoopMixin,
              TrainerTrainLoopMixin,
              TrainerCallbackConfigMixin,
              ):

    def __init__(
            self,
            logger: Union[LightningLoggerBase, bool] = True,
            checkpoint_callback: Union[ModelCheckpoint, bool] = True,
            early_stop_callback: Optional[Union[EarlyStopping, bool]] = None,
            default_save_path: Optional[str] = None,
            gradient_clip_val: float = 0,
            gradient_clip=None,  # backward compatible, todo: remove in v0.8.0
            process_position: int = 0,
            nb_gpu_nodes=None,  # backward compatible, todo: remove in v0.8.0
            num_nodes: int = 1,
            gpus: Optional[Union[List[int], str, int]] = None,
            num_tpu_cores: Optional[int] = None,
            log_gpu_memory: Optional[str] = None,
            show_progress_bar: bool = True,
            overfit_pct: float = 0.0,
            track_grad_norm: int = -1,
            check_val_every_n_epoch: int = 1,
            fast_dev_run: bool = False,
            accumulate_grad_batches: Union[int, Dict[int, int]] = 1,
            max_nb_epochs=None,  # backward compatible, todo: remove in v0.8.0
            min_nb_epochs=None,  # backward compatible, todo: remove in v0.8.0
            max_epochs: int = 1000,
            min_epochs: int = 1,
            max_steps: Optional[int] = None,
            min_steps: Optional[int] = None,
            train_percent_check: float = 1.0,
            val_percent_check: float = 1.0,
            test_percent_check: float = 1.0,
            val_check_interval: Union[float] = 1.0,
            log_save_interval: int = 100,
            row_log_interval: int = 10,
            add_row_log_interval=None,  # backward compatible, todo: remove in v0.8.0
            distributed_backend: Optional[str] = None,
            use_amp=False,  # backward compatible, todo: remove in v0.8.0
            precision: int = 32,
            print_nan_grads: bool = False,
            weights_summary: str = 'full',
            weights_save_path: Optional[str] = None,
            amp_level: str = 'O1',
            nb_sanity_val_steps=None,  # backward compatible, todo: remove in v0.8.0
            num_sanity_val_steps: int = 5,
            truncated_bptt_steps: Optional[int] = None,
            resume_from_checkpoint: Optional[str] = None,
            profiler: Optional[BaseProfiler] = None,
    ):
        r"""

        Customize every aspect of training via flags

        Args:
            logger: Logger for experiment tracking.
                Example::

                    from pytorch_lightning.loggers import TensorBoardLogger

                    # default logger used by trainer
                    logger = TensorBoardLogger(
                        save_dir=os.getcwd(),
                        version=self.slurm_job_id,
                        name='lightning_logs'
                    )

                    Trainer(logger=logger)

            checkpoint_callback: Callback for checkpointing.
                Example::

                    from pytorch_lightning.callbacks import ModelCheckpoint

                    # default used by the Trainer
                    checkpoint_callback = ModelCheckpoint(
                        filepath=os.getcwd(),
                        save_best_only=True,
                        verbose=True,
                        monitor='val_loss',
                        mode='min',
                        prefix=''
                    )

                    trainer = Trainer(checkpoint_callback=checkpoint_callback)

            early_stop_callback: Callback for early stopping. If
                set to ``True``, then the default callback monitoring ``'val_loss'`` is created.
                Will raise an error if ``'val_loss'`` is not found.
                If set to ``False``, then early stopping will be disabled.
                If set to ``None``, then the default callback monitoring ``'val_loss'`` is created.
                If ``'val_loss'`` is not found will work as if early stopping is disabled.
                Default: ``None``.
                Example::

                    from pytorch_lightning.callbacks import EarlyStopping

                    # default used by the Trainer
                    early_stop_callback = EarlyStopping(
                        monitor='val_loss',
                        patience=3,
                        strict=False,
                        verbose=False,
                        mode='min'
                    )

                    trainer = Trainer(early_stop_callback=early_stop_callback)

            default_save_path: Default path for logs and weights when no logger/ckpt_callback passed
                Example::

                    # default used by the Trainer
                    trainer = Trainer(default_save_path=os.getcwd())

            gradient_clip_val: 0 means don't clip.
                Example::

                    # default used by the Trainer
                    trainer = Trainer(gradient_clip_val=0.0)

            gradient_clip:
                .. warning: .. deprecated:: 0.5.0
                    Use `gradient_clip_val` instead. Will remove 0.8.0.

            process_position: orders the tqdm bar when running multiple models on same machine.
                Example::

                    # default used by the Trainer
                    trainer = Trainer(process_position=0)

            num_nodes: number of GPU nodes for distributed training.
                Example::

                    # default used by the Trainer
                    trainer = Trainer(num_nodes=1)

                    # to train on 8 nodes
                    trainer = Trainer(num_nodes=8)

            nb_gpu_nodes:
                ..warning:: .. deprecated:: 0.5.0
                    Use `num_nodes` instead. Will remove 0.8.0.

            gpus: Which GPUs to train on.
                Example::

                    # default used by the Trainer (ie: train on CPU)
                    trainer = Trainer(gpus=None)

                    # int: train on 2 gpus
                    trainer = Trainer(gpus=2)

                    # list: train on GPUs 1, 4 (by bus ordering)
                    trainer = Trainer(gpus=[1, 4])
                    trainer = Trainer(gpus='1, 4') # equivalent

                    # -1: train on all gpus
                    trainer = Trainer(gpus=-1)
                    trainer = Trainer(gpus='-1') # equivalent

                    # combine with num_nodes to train on multiple GPUs across nodes
                    trainer = Trainer(gpus=2, num_nodes=4) # uses 8 gpus in total

            num_tpu_cores: How many TPU cores to train on (1 or 8).
                A single TPU v2 or v3 has 8 cores. A TPU pod has
                up to 2048 cores. A slice of a POD means you get as many cores
                as you request.

                You MUST use DistributedDataSampler with your dataloader for this
                to work. Your effective batch size is batch_size * total tpu cores.

                This parameter can be either 1 or 8.

                Example::

                    # your_trainer_file.py

                    # default used by the Trainer (ie: train on CPU)
                    trainer = Trainer(num_tpu_cores=None)

                    # int: train on a single core
                    trainer = Trainer(num_tpu_cores=1)

                    # int: train on all cores few cores
                    trainer = Trainer(num_tpu_cores=8)

                    # for 8+ cores must submit via xla script with
                    # a max of 8 cores specified. The XLA script
                    # will duplicate script onto each TPU in the POD
                    trainer = Trainer(num_tpu_cores=8)

                    # -1: train on all available TPUs
                    trainer = Trainer(num_tpu_cores=-1)

            To train on more than 8 cores (ie: a POD),
            submit this script using the xla_dist script.

            Example::

                $ python -m torch_xla.distributed.xla_dist
                --tpu=$TPU_POD_NAME
                --conda-env=torch-xla-nightly
                --env=XLA_USE_BF16=1
                -- python your_trainer_file.py

            log_gpu_memory: None, 'min_max', 'all'. Might slow performance
                because it uses the output of nvidia-smi.
                Example::

                    # default used by the Trainer
                    trainer = Trainer(log_gpu_memory=None)

                    # log all the GPUs (on master node only)
                    trainer = Trainer(log_gpu_memory='all')

                    # log only the min and max memory on the master node
                    trainer = Trainer(log_gpu_memory='min_max')

            show_progress_bar: If true shows tqdm progress bar
                Example::

                    # default used by the Trainer
                    trainer = Trainer(show_progress_bar=True)

            overfit_pct: uses this much data of all datasets.
                Example::

                    # default used by the Trainer
                    trainer = Trainer(overfit_pct=0.0)

                    # use only 1% of the train, test, val datasets
                    trainer = Trainer(overfit_pct=0.01)

            track_grad_norm: -1 no tracking. Otherwise tracks that norm
                Example::

                    # default used by the Trainer
                    trainer = Trainer(track_grad_norm=-1)

                    # track the 2-norm
                    trainer = Trainer(track_grad_norm=2)

            check_val_every_n_epoch: Check val every n train epochs.
                Example::

                    # default used by the Trainer
                    trainer = Trainer(check_val_every_n_epoch=1)

                    # run val loop every 10 training epochs
                    trainer = Trainer(check_val_every_n_epoch=10)

            fast_dev_run: runs 1 batch of train, test  and val to find any bugs (ie: a sort of unit test).
                Example::

                    # default used by the Trainer
                    trainer = Trainer(fast_dev_run=False)

                    # runs 1 train, val, test  batch and program ends
                    trainer = Trainer(fast_dev_run=True)

            accumulate_grad_batches: Accumulates grads every k batches or as set up in the dict.
                Example::

                    # default used by the Trainer (no accumulation)
                    trainer = Trainer(accumulate_grad_batches=1)

                    # accumulate every 4 batches (effective batch size is batch*4)
                    trainer = Trainer(accumulate_grad_batches=4)

                    # no accumulation for epochs 1-4. accumulate 3 for epochs 5-10. accumulate 20 after that
                    trainer = Trainer(accumulate_grad_batches={5: 3, 10: 20})

            max_epochs: Stop training once this number of epochs is reached.
                Example::

                    # default used by the Trainer
                    trainer = Trainer(max_epochs=1000)

            max_nb_epochs:
                .. warning:: .. deprecated:: 0.5.0
                    Use `max_epochs` instead. Will remove 0.8.0.

            min_epochs: Force training for at least these many epochs
                Example::

                    # default used by the Trainer
                    trainer = Trainer(min_epochs=1)

            min_nb_epochs:
                .. warning:: .. deprecated:: 0.5.0
                    Use `min_nb_epochs` instead. Will remove 0.8.0.

            max_steps: Stop training after this number of steps. Disabled by default (None).
                Training will stop if max_steps or max_epochs have reached (earliest).
                Example::

                    # Stop after 100 steps
                    trainer = Trainer(max_steps=100)

            min_steps: Force training for at least these number of steps. Disabled by default (None).
                Trainer will train model for at least min_steps or min_epochs (latest).
                Example::

                    # Run at least for 100 steps (disable min_epochs)
                    trainer = Trainer(min_steps=100, min_epochs=0)

            train_percent_check: How much of training dataset to check.
                Useful when debugging or testing something that happens at the end of an epoch.
                Example::

                    # default used by the Trainer
                    trainer = Trainer(train_percent_check=1.0)

                    # run through only 25% of the training set each epoch
                    trainer = Trainer(train_percent_check=0.25)

            val_percent_check: How much of validation dataset to check.
                Useful when debugging or testing something that happens at the end of an epoch.
                Example::

                    # default used by the Trainer
                    trainer = Trainer(val_percent_check=1.0)

                    # run through only 25% of the validation set each epoch
                    trainer = Trainer(val_percent_check=0.25)

            test_percent_check: How much of test dataset to check.
                Useful when debugging or testing something that happens at the end of an epoch.
                Example::

                    # default used by the Trainer
                    trainer = Trainer(test_percent_check=1.0)

                    # run through only 25% of the test set each epoch
                    trainer = Trainer(test_percent_check=0.25)

            val_check_interval: How often within one training epoch to check the validation set
                If float, % of tng epoch. If int, check every n batch
                Example::

                    # default used by the Trainer
                    trainer = Trainer(val_check_interval=1.0)

                    # check validation set 4 times during a training epoch
                    trainer = Trainer(val_check_interval=0.25)

                    # check validation set every 1000 training batches
                    # use this when using iterableDataset and your dataset has no length
                    # (ie: production cases with streaming data)
                    trainer = Trainer(val_check_interval=1000)

            log_save_interval: Writes logs to disk this often
                Example::

                    # default used by the Trainer
                    trainer = Trainer(log_save_interval=100)

            row_log_interval: How often to add logging rows (does not write to disk)
                Example::

                    # default used by the Trainer
                    trainer = Trainer(row_log_interval=10)

            add_row_log_interval:
                .. warning:: .. deprecated:: 0.5.0
                    Use `row_log_interval` instead. Will remove 0.8.0.

            distributed_backend: The distributed backend to use.
                Options: 'dp', 'ddp', 'ddp2'.
                Example::

                    # default used by the Trainer
                    trainer = Trainer(distributed_backend=None)

                    # dp = DataParallel (split a batch onto k gpus on same machine).
                    trainer = Trainer(gpus=2, distributed_backend='dp')

                    # ddp = DistributedDataParallel
                    # Each gpu trains by itself on a subset of the data.
                    # Gradients sync across all gpus and all machines.
                    trainer = Trainer(gpus=2, num_nodes=2, distributed_backend='ddp')

                    # ddp2 = DistributedDataParallel + dp
                    # behaves like dp on every node
                    # syncs gradients across nodes like ddp
                    # useful for things like increasing the number of negative samples
                    trainer = Trainer(gpus=2, num_nodes=2, distributed_backend='ddp2')

            use_amp:
                .. warning:: .. deprecated:: 0.6.1
                    Use `precision` instead. Will remove 0.8.0.

            precision: Full precision (32), half precision (16).
                Can be used on CPU, GPU or TPUs.

                If used on TPU will use torch.bfloat16 but tensor printing
                will still show torch.float32.

                Example::

                    # default used by the Trainer
                    trainer = Trainer(precision=32)

                    # 16-bit precision
                    trainer = Trainer(precision=16)

                    # one day
                    trainer = Trainer(precision=8|4|2)

            print_nan_grads: Prints gradients with nan values
                Example::

                    # default used by the Trainer
                    trainer = Trainer(print_nan_grads=False)

            weights_summary: Prints a summary of the weights when training begins.
                Options: 'full', 'top', None.
                Example::

                    # default used by the Trainer (ie: print all weights)
                    trainer = Trainer(weights_summary='full')

                    # print only the top level modules
                    trainer = Trainer(weights_summary='top')

                    # don't print a summary
                    trainer = Trainer(weights_summary=None)

            weights_save_path: Where to save weights if specified.
                Example::

                    # default used by the Trainer
                    trainer = Trainer(weights_save_path=os.getcwd())

                    # save to your custom path
                    trainer = Trainer(weights_save_path='my/path')

                    # if checkpoint callback used, then overrides the weights path
                    # **NOTE: this saves weights to some/path NOT my/path
                    checkpoint_callback = ModelCheckpoint(filepath='some/path')
                    trainer = Trainer(
                        checkpoint_callback=checkpoint_callback,
                        weights_save_path='my/path'
                    )

            amp_level: The optimization level to use (O1, O2, etc...).
                Check nvidia docs for level (https://nvidia.github.io/apex/amp.html#opt-levels)
                Example::

                    # default used by the Trainer
                    trainer = Trainer(amp_level='O1')

            num_sanity_val_steps: Sanity check runs n batches of val before starting the training routine.
                This catches any bugs in your validation without having to wait for the first validation check.
                The Trainer uses 5 steps by default. Turn it off or modify it here.
                Example::

                    # default used by the Trainer
                    trainer = Trainer(num_sanity_val_steps=5)

                    # turn it off
                    trainer = Trainer(num_sanity_val_steps=0)

            nb_sanity_val_steps:
                .. warning:: .. deprecated:: 0.5.0
                    Use `num_sanity_val_steps` instead. Will remove 0.8.0.

            truncated_bptt_steps: Truncated back prop breaks performs backprop every k steps of
                a much longer sequence If this is enabled, your batches will automatically get truncated
                and the trainer will apply Truncated Backprop to it. Make sure your batches have a sequence
                dimension. (`Williams et al. "An efficient gradient-based algorithm for on-line training of
                recurrent network trajectories."
                <http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.56.7941&rep=rep1&type=pdf>`_)
                Example::

                    # default used by the Trainer (ie: disabled)
                    trainer = Trainer(truncated_bptt_steps=None)

                    # backprop every 5 steps in a batch
                    trainer = Trainer(truncated_bptt_steps=5)


                Lightning takes care to split your batch along the time-dimension.

                .. note:: If you need to modify how the batch is split,
                    override :meth:`pytorch_lightning.core.LightningModule.tbptt_split_batch`.

                .. note:: Using this feature requires updating your LightningModule's
                    :meth:`pytorch_lightning.core.LightningModule.training_step` to include a `hiddens` arg.

            resume_from_checkpoint: To resume training from a specific checkpoint pass in the path here.k
                Example::

                    # default used by the Trainer
                    trainer = Trainer(resume_from_checkpoint=None)

                    # resume from a specific checkpoint
                    trainer = Trainer(resume_from_checkpoint='some/path/to/my_checkpoint.ckpt')
            profiler:  To profile individual steps during training and assist in
                identifying bottlenecks.
                Example::

                    from pytorch_lightning.profiler import Profiler, AdvancedProfiler

                    # default used by the Trainer
                    trainer = Trainer(profiler=None)

                    # to profile standard training events
                    trainer = Trainer(profiler=True)

                    # equivalent to profiler=True
                    profiler = Profiler()
                    trainer = Trainer(profiler=profiler)

                    # advanced profiler for function-level stats
                    profiler = AdvancedProfiler()
                    trainer = Trainer(profiler=profiler)

        .. warning:: Following arguments become deprecated and they will be removed in v0.8.0:

            - `nb_sanity_val_steps`

        """

        # Transfer params
        # Backward compatibility
        if nb_gpu_nodes is not None:
            warnings.warn("`nb_gpu_nodes` has renamed to `num_nodes` since v0.5.0"
                          " and this method will be removed in v0.8.0", DeprecationWarning)
            if not num_nodes:  # in case you did not set the proper value
                num_nodes = nb_gpu_nodes
        self.num_gpu_nodes = num_nodes

        self.log_gpu_memory = log_gpu_memory

        # Backward compatibility
        if gradient_clip is not None:
            warnings.warn("`gradient_clip` has renamed to `gradient_clip_val` since v0.5.0"
                          " and this method will be removed in v0.8.0", DeprecationWarning)
            if not gradient_clip_val:  # in case you did not set the proper value
                gradient_clip_val = gradient_clip
        self.gradient_clip_val = gradient_clip_val

        self.check_val_every_n_epoch = check_val_every_n_epoch
        self.track_grad_norm = track_grad_norm
        self.on_gpu = True if (gpus and torch.cuda.is_available()) else False

        # tpu config
        self.on_tpu = num_tpu_cores is not None
        self.num_tpu_cores = num_tpu_cores
        assert num_tpu_cores in [1, 8, None], 'num_tpu_cores can only be 1 or 8'

        self.process_position = process_position
        self.weights_summary = weights_summary

        # Backward compatibility
        if max_nb_epochs is not None:
            warnings.warn("`max_nb_epochs` has renamed to `max_epochs` since v0.5.0"
                          " and this method will be removed in v0.8.0", DeprecationWarning)
            if not max_epochs:  # in case you did not set the proper value
                max_epochs = max_nb_epochs
        self.max_epochs = max_epochs

        # Backward compatibility
        if min_nb_epochs is not None:
            warnings.warn("`min_nb_epochs` has renamed to `min_epochs` since v0.5.0"
                          " and this method will be removed in v0.8.0", DeprecationWarning)
            if not min_epochs:  # in case you did not set the proper value
                min_epochs = min_nb_epochs
        self.min_epochs = min_epochs

        self.max_steps = max_steps
        self.min_steps = min_steps

        # Backward compatibility
        if nb_sanity_val_steps is not None:
            warnings.warn("`nb_sanity_val_steps` has renamed to `num_sanity_val_steps` since v0.5.0"
                          " and this method will be removed in v0.8.0", DeprecationWarning)
            if not num_sanity_val_steps:  # in case you did not set the proper value
                num_sanity_val_steps = nb_sanity_val_steps

        self.num_sanity_val_steps = num_sanity_val_steps
        self.print_nan_grads = print_nan_grads
        self.truncated_bptt_steps = truncated_bptt_steps
        self.resume_from_checkpoint = resume_from_checkpoint
        self.shown_warnings = set()

        self.fast_dev_run = fast_dev_run
        if self.fast_dev_run:
            self.num_sanity_val_steps = 1
            self.max_epochs = 1
            m = '''
            Running in fast_dev_run mode: will run a full train,
            val loop using a single batch
            '''
            log.info(m)

        # set default save path if user didn't provide one
        self.default_save_path = default_save_path
        if self.default_save_path is None:
            self.default_save_path = os.getcwd()

        # training bookeeping
        self.total_batch_idx = 0
        self.running_loss = []
        self.avg_loss = 0
        self.batch_idx = 0
        self.tqdm_metrics = {}
        self.callback_metrics = {}
        self.num_val_batches = 0
        self.num_training_batches = 0
        self.num_test_batches = 0
        self.get_train_dataloader = None
        self.get_test_dataloaders = None
        self.get_val_dataloaders = None
        self.is_iterable_train_dataloader = False

        # training state
        self.model = None
        self.testing = False
        self.disable_validation = False
        self.lr_schedulers = []
        self.optimizers = None
        self.global_step = 0
        self.current_epoch = 0
        self.total_batches = 0

        # configure logger
        self.configure_logger(logger)

        # configure profiler
        if profiler is True:
            profiler = Profiler()
        self.profiler = profiler or PassThroughProfiler()

        # configure early stop callback
        # creates a default one if none passed in
        self.configure_early_stopping(early_stop_callback)

        self.reduce_lr_on_plateau_scheduler = None

        # configure checkpoint callback
        self.checkpoint_callback = checkpoint_callback
        self.weights_save_path = weights_save_path

        # accumulated grads
        self.configure_accumulated_gradients(accumulate_grad_batches)

        # allow int, string and gpu list
        self.data_parallel_device_ids = parse_gpu_ids(gpus)
        self.root_gpu = determine_root_gpu_device(self.data_parallel_device_ids)

        # tpu state flags
        self.use_tpu = False
        self.tpu_local_core_rank = None
        self.tpu_global_core_rank = None

        # distributed backend choice
        self.use_ddp = False
        self.use_ddp2 = False
        self.use_dp = False
        self.single_gpu = False
        self.distributed_backend = distributed_backend
        self.set_distributed_mode(distributed_backend, num_nodes)

        # override dist backend when using tpus
        if self.on_tpu:
            self.init_tpu()
            self.current_tpu_idx = None

        # init flags for SLURM+ddp to work
        self.proc_rank = 0
        self.world_size = 1
        self.node_rank = 0
        self.configure_slurm_ddp(num_nodes)

        # nvidia setup
        self.set_nvidia_flags(self.is_slurm_managing_tasks, self.data_parallel_device_ids)

        # can't init progress bar here because starting a new process
        # means the progress_bar won't survive pickling
        self.show_progress_bar = show_progress_bar

        # logging
        self.log_save_interval = log_save_interval
        self.val_check_interval = val_check_interval

        # backward compatibility
        if add_row_log_interval is not None:
            warnings.warn("`add_row_log_interval` has renamed to `row_log_interval` since v0.5.0"
                          " and this method will be removed in v0.8.0", DeprecationWarning)
            if not row_log_interval:  # in case you did not set the proper value
                row_log_interval = add_row_log_interval
        self.row_log_interval = row_log_interval

        # how much of the data to use
        self.determine_data_use_amount(train_percent_check, val_percent_check,
                                       test_percent_check, overfit_pct)

        # 16 bit mixed precision training using apex
        self.amp_level = amp_level
        self.precision = precision
        if self.precision == 16:
            use_amp = True
        self.init_amp(use_amp)

    @property
    def slurm_job_id(self) -> int:
        try:
            job_id = os.environ['SLURM_JOB_ID']
            job_id = int(job_id)
        except Exception:
            job_id = None
        return job_id

    def __parse_gpu_ids(self, gpus):
        """Parse GPUs id.

        :param list|str|int gpus: input GPU ids
        :return list(int):
        """
        # if gpus = -1 then use all available devices
        # otherwise, split the string using commas
        if gpus is not None:
            if isinstance(gpus, list):
                gpus = gpus
            elif isinstance(gpus, str):
                if gpus == '-1':
                    gpus = list(range(0, torch.cuda.device_count()))
                else:
                    gpus = [int(x.strip()) for x in gpus.split(',')]
            elif isinstance(gpus, int):
                gpus = gpus
            else:
                raise ValueError('`gpus` has to be a string, int or list of ints')

        return gpus

    def __set_root_gpu(self, gpus):
        if gpus is None:
            return None

        # set root gpu
        root_gpu = 0
        if isinstance(gpus, list):
            root_gpu = gpus[0]

        return root_gpu

    @property
    def num_gpus(self) -> int:
        gpus = self.data_parallel_device_ids
        if gpus is None:
            return 0
        return len(gpus)

    @property
    def data_parallel(self) -> bool:
        return self.use_dp or self.use_ddp or self.use_ddp2

    @property
    def training_tqdm_dict(self) -> dict:
        """Read-only for tqdm metrics.
        :return:
        """
        ref_model = self.model if not self.data_parallel else self.model.module

        return dict(**ref_model.get_tqdm_dict(), **self.tqdm_metrics)

    @property
    def tng_tqdm_dic(self):
        """Read-only for tqdm metrics.

        :return: dictionary

        .. warning:: .. deprecated:: 0.5.0
                    Use `training_tqdm_dict` instead. Will remove 0.8.0.
        """
        warnings.warn("`tng_tqdm_dic` has renamed to `training_tqdm_dict` since v0.5.0"
                      " and this method will be removed in v0.8.0", DeprecationWarning)
        return self.training_tqdm_dict

    # -----------------------------
    # MODEL TRAINING
    # -----------------------------
    def fit(
            self,
            model: LightningModule,
            train_dataloader: Optional[DataLoader] = None,
            val_dataloader: Optional[DataLoader] = None,
            test_dataloader: Optional[DataLoader] = None
    ):
        r"""
        Runs the full optimization routine.

        Args:
            model: Model to fit.

            train_dataloader: A Pytorch
                DataLoader with training samples. If the model has
                a predefined train_dataloader method this will be skipped.

            val_dataloader: Either a single
                Pytorch Dataloader or a list of them, specifying validation samples.
                If the model has a predefined val_dataloader method this will be skipped

            test_dataloader: Either a single
                Pytorch Dataloader or a list of them, specifying validation samples.
                If the model has a predefined val_dataloader method this will be skipped

        Example::

            # Option 1,
            # Define the train_dataloader(), test_dataloader() and val_dataloader() fxs
            # in the lightningModule
            # RECOMMENDED FOR MOST RESEARCH AND APPLICATIONS TO MAINTAIN READABILITY
            trainer = Trainer()
            model = LightningModule()
            trainer.fit(model)

            # Option 2
            # in production cases we might want to pass different datasets to the same model
            # Recommended for PRODUCTION SYSTEMS
            train, val, test = DataLoader(...), DataLoader(...), DataLoader(...)
            trainer = Trainer()
            model = LightningModule()
            trainer.fit(model, train_dataloader=train,
                        val_dataloader=val, test_dataloader=test)

            # Option 1 & 2 can be mixed, for example the training set can be
            # defined as part of the model, and validation/test can then be
            # feed to .fit()

        """

        # Update the dataloader attributes of the model with the ones supplied here,
        # if they are not already defined in model
        _set_dataloader(model, train_dataloader, 'train_dataloader')
        _set_dataloader(model, val_dataloader, 'val_dataloader')
        _set_dataloader(model, test_dataloader, 'test_dataloader')

        # when using multi-node or DDP within a node start each module in a separate process
        if self.use_ddp2:
            task = int(os.environ['SLURM_LOCALID'])
            self.ddp_train(task, model)

        elif self.use_ddp:
            if self.is_slurm_managing_tasks:
                task = int(os.environ['SLURM_LOCALID'])
                self.ddp_train(task, model)
            else:
                mp.spawn(self.ddp_train, nprocs=self.num_gpus, args=(model,))

        # 1 gpu or dp option triggers training using DP module
        # easier to avoid NCCL issues
        elif self.use_dp:
            self.dp_train(model)

        elif self.single_gpu:
            self.single_gpu_train(model)

        elif self.use_tpu:
            log.info(f'training on {self.num_tpu_cores} TPU cores')

            #  COLAB_GPU is an env var available by default in Colab environments.
            start_method = 'fork' if os.getenv('COLAB_GPU') else 'spawn'
            xmp.spawn(self.tpu_train, args=(model,), nprocs=self.num_tpu_cores, start_method=start_method)

        # ON CPU
        else:
            # run through amp wrapper
            if self.use_amp:
                raise MisconfigurationException('amp + cpu is not supported.  Please use a GPU option')

            # CHOOSE OPTIMIZER
            # allow for lr schedulers as well
            self.optimizers, self.lr_schedulers = self.init_optimizers(model.configure_optimizers())

            self.run_pretrain_routine(model)

        # return 1 when finished
        # used for testing or when we need to know that training succeeded
        return 1

    def init_optimizers(
            self,
            optimizers: Union[Optimizer, Tuple[List, List], List[Optimizer], Tuple[Optimizer]]
    ) -> Tuple[List, List]:

        # single optimizer
        if isinstance(optimizers, Optimizer):
            return [optimizers], []

        # two lists
        if len(optimizers) == 2 and isinstance(optimizers[0], list):
            optimizers, lr_schedulers = optimizers
            lr_schedulers, self.reduce_lr_on_plateau_scheduler = self.configure_schedulers(lr_schedulers)
            return optimizers, lr_schedulers

        # single list or tuple
        if isinstance(optimizers, (list, tuple)):
            return optimizers, []

    def configure_schedulers(self, schedulers: list):
        for i, scheduler in enumerate(schedulers):
            if isinstance(scheduler, torch.optim.lr_scheduler.ReduceLROnPlateau):
                reduce_lr_on_plateau_scheduler = schedulers.pop(i)
                return schedulers, reduce_lr_on_plateau_scheduler
        return schedulers, None

    def run_pretrain_routine(self, model: LightningModule):
        """Sanity check a few things before starting actual training.

        Args:
            model: The model to run sanity test on.
        """
        ref_model = model
        if self.data_parallel:
            ref_model = model.module

        # give model convenience properties
        ref_model.trainer = self

        # set local properties on the model
        self.copy_trainer_model_properties(ref_model)

        # link up experiment object
        if self.logger is not None:
            ref_model.logger = self.logger

            # save exp to get started
            if hasattr(ref_model, "hparams"):
                self.logger.log_hyperparams(ref_model.hparams)

            self.logger.save()

        if self.use_ddp or self.use_ddp2:
            dist.barrier()

        # wait for all models to restore weights
        if self.on_tpu and XLA_AVAILABLE:
            # wait for all processes to catch up
            torch_xla.core.xla_model.rendezvous()

        # set up checkpoint callback
        self.configure_checkpoint_callback()

        # register auto-resubmit when on SLURM
        self.register_slurm_signal_handlers()

        # transfer data loaders from model
        self.get_dataloaders(ref_model)

        # print model summary
        if self.proc_rank == 0 and self.weights_summary is not None:
            if self.weights_summary in ['full', 'top']:
                ref_model.summarize(mode=self.weights_summary)
            else:
                m = "weights_summary can be None, 'full' or 'top'"
                raise MisconfigurationException(m)

        # track model now.
        # if cluster resets state, the model will update with the saved weights
        self.model = model

        # restore training and model before hpc call
        self.restore_weights(model)

        # when testing requested only run test and return
        if self.testing:
            self.run_evaluation(test=True)
            return

        # check if we should run validation during training
        self.disable_validation = ((self.num_val_batches == 0 or
                                    not self.is_overriden('validation_step')) and
                                   not self.fast_dev_run)

        # run tiny validation (if validation defined)
        # to make sure program won't crash during val
        ref_model.on_sanity_check_start()
        ref_model.on_train_start()
        if not self.disable_validation and self.num_sanity_val_steps > 0:
            # init progress bars for validation sanity check
            pbar = tqdm(desc='Validation sanity check',
                             total=self.num_sanity_val_steps * len(self.get_val_dataloaders()),
                             leave=False, position=2 * self.process_position,
                             disable=not self.show_progress_bar, dynamic_ncols=True)
            self.main_progress_bar = pbar
            # dummy validation progress bar
            self.val_progress_bar = tqdm(disable=True)

            eval_results = self.evaluate(model, self.get_val_dataloaders(),
                                         self.num_sanity_val_steps, False)
            _, _, _, callback_metrics, _ = self.process_output(eval_results)

            # close progress bars
            self.main_progress_bar.close()
            self.val_progress_bar.close()

            if self.enable_early_stop:
                self.early_stop_callback.check_metrics(callback_metrics)

        # init progress bar
        pbar = tqdm(leave=True, position=2 * self.process_position,
                    disable=not self.show_progress_bar, dynamic_ncols=True,
                    file=sys.stdout)
        self.main_progress_bar = pbar

        # clear cache before training
        if self.on_gpu:
            torch.cuda.empty_cache()

        # CORE TRAINING LOOP
        self.train()

    def test(self, model: Optional[LightningModule] = None):
        r"""

        Separates from fit to make sure you never run on your test set until you want to.

        Args:
            model: The model to test.

        Example::

            # Option 1
            # run test after fitting
            trainer = Trainer()
            model = LightningModule()

            trainer.fit()
            trainer.test()

            # Option 2
            # run test from a loaded model
            model = LightningModule.load_from_checkpoint('path/to/checkpoint.ckpt')
            trainer = Trainer()
            trainer.test(model)
        """
        self.testing = True
        if model is not None:
            self.fit(model)
        else:
            self.run_evaluation(test=True)


def _set_dataloader(model, dataloader, attribute):
    r'''
    Check dataloaders passed to .fit() method if they are pytorch DataLoader
    objects and whether or not we should overright the corresponding dataloader
    in the model

    Args:
        model (LightningModule): The model to check

        dataloader: If a pytorch dataloader (or a list of pytorch dataloaders)
            is passed, it will be incorporate into the model as model.attribute.
            If attribute alreay exist it will warn the userpass. If not a
            dataloader will throw an error

        attribute (str): The attribute to save the dataloader under

    '''
    # Check if attribute comes directly from base class or
    # derived in user subclass
    if LightningModule.__qualname__ in getattr(model, attribute).__qualname__:
        # Val and test should be list of dataloaders
        dataloader = dataloader if attribute == 'train_dataloader' or \
            (attribute != 'train_dataloader' and isinstance(dataloader, list)) else [dataloader]

        # Check we are given valid dataloaders
        is_dataloader = isinstance(dataloader, torch.utils.data.DataLoader)
        is_dataloader_list = isinstance(dataloader, list)
        if is_dataloader_list:
            valid_loaders = all(isinstance(d, torch.utils.data.DataLoader) for d in dataloader)
        if is_dataloader or is_dataloader_list and valid_loaders:

            # Overwrite abstract methods
            dl = lambda: dataloader
            dl.__name__ = attribute
            setattr(model, attribute, dl)

        elif dataloader and dataloader != [None]:
            raise ValueError(f'`{attribute}` needs to be an instance of '
                             '`torch.utils.data.DataLoader` or a list of '
                             'DataLoaders, instead got %r`' % dataloader)

    elif dataloader:  # if default (None) is passed, do not warn the user
        warnings.warn(f'Model has predefined `{attribute}`,'
                      f' will skip `{attribute}={dataloader}` passed to fit method.')