Пример #1
0
def train(forward_step_func, model, optimizer, lr_scheduler,
          train_data_iterator, valid_data_iterator):
    """Train the model function."""
    args = get_args()
    timers = get_timers()

    # Turn on training mode which enables dropout.
    model.train()

    # Tracking loss.
    total_loss_dict = {}

    # Iterations.
    iteration = args.iteration

    timers('interval time').start()
    report_memory_flag = True
    while iteration < args.train_iters:
        loss_dict, skipped_iter = train_step(forward_step_func,
                                             train_data_iterator, model,
                                             optimizer, lr_scheduler)
        iteration += 1

        # Logging.
        loss_scale = None
        if args.fp16:
            loss_scale = optimizer.cur_scale if args.deepspeed else optimizer.loss_scale
        report_memory_flag = training_log(loss_dict, total_loss_dict,
                                          optimizer.param_groups[0]['lr'],
                                          iteration, loss_scale,
                                          report_memory_flag, skipped_iter)

        # Autoresume
        if args.adlr_autoresume and \
           (iteration % args.adlr_autoresume_interval == 0):
            check_adlr_autoresume_termination(iteration, model, optimizer,
                                              lr_scheduler)

        # Checkpointing
        if args.save and args.save_interval and \
           iteration % args.save_interval == 0:
            save_checkpoint(iteration, model, optimizer, lr_scheduler)

        # Evaluation
        if args.eval_interval and iteration % args.eval_interval == 0 and \
           args.do_valid:
            prefix = 'iteration {}'.format(iteration)
            evaluate_and_print_results(prefix, forward_step_func,
                                       valid_data_iterator, model, iteration,
                                       False)

        if args.exit_interval and iteration % args.exit_interval == 0:
            torch.distributed.barrier()
            time_str = datetime.now().strftime('%Y-%m-%d %H:%M:%S')
            rank = torch.distributed.get_rank()
            print_rank_0('rank: {} | time: {} | exiting the program at '
                         'iteration {}'.format(rank, time_str, iteration))
            sys.exit()

    return iteration
Пример #2
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 def save(self, context: DeepSpeedTrialContext, path: pathlib.Path) -> None:
     self.neox_args.save = str(path)
     save_checkpoint(
         neox_args=self.neox_args,
         iteration=self.neox_args.iteration,
         model=self.model,
         optimizer=self.optimizer,
         lr_scheduler=self.lr_scheduler,
     )
Пример #3
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def save_checkpoint_and_time(iteration, model, optimizer, lr_scheduler):
    timers = get_timers()
    # Extra barrier is added to make sure
    # all ranks report the max time.
    torch.distributed.barrier()
    timers('save checkpoint').start()
    save_checkpoint(iteration, model, optimizer, lr_scheduler)
    torch.distributed.barrier()
    timers('save checkpoint').stop()
    timers.log(['save checkpoint'])
Пример #4
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def check_adlr_autoresume_termination(iteration, model, optimizer,
                                      lr_scheduler):
    """Check for autoresume signal and exit if it is received."""
    args = get_args()
    autoresume = get_adlr_autoresume()
    # Add barrier to ensure consistnecy.
    torch.distributed.barrier()
    if autoresume.termination_requested():
        if args.save:
            save_checkpoint(iteration, model, optimizer, lr_scheduler)
        print_rank_0(">>> autoresume termination request found!")
        if torch.distributed.get_rank() == 0:
            autoresume.request_resume()
        print_rank_0(">>> training terminated. Returning")
        sys.exit(0)
Пример #5
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def run_checkpoint_test(yaml_list=None, param_dict=None):

    from megatron.checkpointing import load_checkpoint
    from megatron.checkpointing import save_checkpoint

    model, optimizer, lr_scheduler, args_loaded = model_setup(yaml_list,
                                                              param_dict,
                                                              clear_data=True)

    # save model checkpoint
    save_checkpoint(
        neox_args=args_loaded,
        iteration=42,
        model=model,
        optimizer=optimizer,
        lr_scheduler=lr_scheduler,
    )

    # reload model from checkpoint
    (
        reloaded_model,
        reloaded_optimizer,
        reloaded_lr_scheduler,
        args_reloaded,
    ) = model_setup(yaml_list, param_dict, clear_data=False)
    iteration = load_checkpoint(
        neox_args=args_reloaded,
        model=reloaded_model,
        optimizer=reloaded_optimizer,
        lr_scheduler=reloaded_lr_scheduler,
    )

    # ensure same checkpoint is loaded
    assert (iteration == 42
            ), "run_checkpoint_test() iteration loaded from checkpoint correct"

    # check all weight groups are the same
    for idx, ((n1, p1), (n2, p2)) in enumerate(
            zip(
                list(model.module.named_parameters()),
                list(reloaded_model.module.named_parameters()),
            )):
        assert n1 == n2
        params_equal = (p1 == p2).all().item()
        assert params_equal, "run_checkpoint_test() params equal: " + str(n1)
def _train(model, optimizer, lr_scheduler, forward_step, train_dataloader,
           valid_dataloader, end_of_epoch_callback):
    """Train the model."""
    args = get_args()
    timers = get_timers()

    # Turn on training mode which enables dropout.
    model.train()

    # Tracking loss.
    losses_dict_sum = {}

    # Starting epoch and iteration
    start_epoch = args.iteration // args.train_iters_per_epoch
    start_iteration = args.iteration % args.train_iters_per_epoch
    iteration = args.iteration

    # Memory reporting flag.
    report_memory_flag = True

    # For each remaining epoch
    timers('interval time').start()
    for epoch in range(start_epoch, args.epochs):
        print_rank_0('working on epoch {} ...'.format(epoch + 1))

        # Set the data loader epoch to shuffle the index iterator.
        train_dataloader.sampler.set_epoch(args.seed + epoch)

        # For all the batches in the dataset.
        for iteration_, batch in enumerate(train_dataloader):

            # Ignore the iterations before starting value
            if iteration_ < start_iteration:
                continue
            # Set to zero so the next epoch does not skip any batches.
            start_iteration = 0

            # Train for one step.
            losses_dict, _ = train_step(forward_step, batch, model, optimizer,
                                        lr_scheduler)
            iteration += 1

            # Logging.
            report_memory_flag = training_log(losses_dict, losses_dict_sum,
                                              optimizer.param_groups[0]['lr'],
                                              iteration, optimizer.loss_scale,
                                              report_memory_flag)

            # Autoresume
            if args.adlr_autoresume and \
               (iteration % args.adlr_autoresume_interval == 0):
                check_adlr_autoresume_termination(iteration, model, optimizer,
                                                  lr_scheduler)

            # Checkpointing
            if args.save and args.save_interval and \
               iteration % args.save_interval == 0:
                save_checkpoint(iteration, model, optimizer, lr_scheduler)

            # Evaluation
            if args.eval_interval and iteration % args.eval_interval == 0:
                prefix = 'iteration {}'.format(iteration)
                evaluate_and_print_results(prefix, forward_step,
                                           valid_dataloader, model, iteration,
                                           False)

        # Checkpointing at the end of each epoch.
        if args.save:
            save_checkpoint(iteration, model, optimizer, lr_scheduler)

        # Callback at the end of each epoch.
        if end_of_epoch_callback is not None:
            end_of_epoch_callback(model, epoch)
Пример #7
0
def pretrain(train_valid_test_dataset_provider, model_provider,
             forward_step_func, extra_args_provider=None, args_defaults={}):
    """Main training program.

    This function will run the followings in the order provided:
        1) initialize Megatron.
        2) setup model, optimizer and lr schedule using the model_provider.
        3) call train_val_test_data_provider to get train/val/test datasets.
        4) train the modle using the forward_step_func.

    Arguments:
        train_valid_test_dataset_provider: a function that takes the size of
            train/valid/test dataset and returns `train, valid, test` datasets.
        model_provider: a function that returns a vanilla version of the
            model. By vanilla we mean a simple model on cpu with no fp16 or ddp.
        forward_step_func: a function that takes a `data iterator` and `model`,
            and returns a `loss` scalar with a dictionary with key:values being
            the info we would like to monitor during training, for example
            `lm-loss: value`. We also require that this function add
            `batch generator` to the timers class.
        extra_args_provider: a function that takes a parser and adds arguments
            to it. It is used for programs to add their own arguments.
        args_defaults: a dictionary from argument-name to argument-value. It
            to set already parse arguments.
    """

    # Initalize and get arguments, timers, and Tensorboard writer.
    initialize_megatron(extra_args_provider=extra_args_provider,
                        args_defaults=args_defaults)

    args = get_args()
    timers = get_timers()

    # Model, optimizer, and learning rate.
    timers('model and optimizer').start()
    model, optimizer, lr_scheduler = setup_model_and_optimizer(model_provider)
    timers('model and optimizer').stop()

    # Data stuff.
    timers('train/valid/test data iterators').start()
    train_data_iterator, valid_data_iterator, test_data_iterator \
        = build_train_valid_test_data_iterators(
            train_valid_test_dataset_provider)
    timers('train/valid/test data iterators').stop()

    # Print setup timing.
    print_rank_0('done with setups ...')
    timers.log(['model and optimizer', 'train/valid/test data iterators'])
    print_rank_0('training ...')

    iteration = 0
    if args.do_train and args.train_iters > 0:
        iteration = train(forward_step_func,
                          model, optimizer, lr_scheduler,
                          train_data_iterator, valid_data_iterator)

    if args.do_valid:
        prefix = 'the end of training for val data'
        evaluate_and_print_results(prefix, forward_step_func,
                                   valid_data_iterator, model,
                                   iteration, False)

    if args.save and iteration != 0:
        save_checkpoint(iteration, model, optimizer, lr_scheduler)

    if args.do_test:
        # Run on test data.
        prefix = 'the end of training for test data'
        evaluate_and_print_results(prefix, forward_step_func,
                                   test_data_iterator, model,
                                   0, True)
Пример #8
0
def pretrain(train_valid_test_dataset_provider,
             model_provider,
             forward_step_func,
             extra_args_provider=None,
             args_defaults={}):
    """Main training program.

    This function will run the followings in the order provided:
        1) initialize Megatron.
        2) setup model, optimizer and lr schedule using the model_provider.
        3) call train_val_test_data_provider to get train/val/test datasets.
        4) train the modle using the forward_step_func.

    Arguments:
        train_valid_test_dataset_provider: a function that takes the size of
            train/valid/test dataset and returns `train, valid, test` datasets.
        model_provider: a function that returns a vanilla version of the
            model. By vanilla we mean a simple model on cpu with no fp16 or ddp.
        forward_step_func: a function that takes a `data iterator` and `model`,
            and returns a `loss` scalar with a dictionary with key:values being
            the info we would like to monitor during training, for example
            `lm-loss: value`. We also require that this function add
            `batch generator` to the timers class.
        extra_args_provider: a function that takes a parser and adds arguments
            to it. It is used for programs to add their own arguments.
        args_defaults: a dictionary from argument-name to argument-value. It
            to set already parse arguments.
    """

    # Initalize and get arguments, timers, and Tensorboard writer.
    initialize_megatron(extra_args_provider=extra_args_provider,
                        args_defaults=args_defaults)

    # Adjust the startup time so it reflects the largest value.
    # This will be closer to what scheduler will see (outside of
    # image ... launches.
    global _TRAIN_START_TIME
    start_time_tensor = torch.cuda.FloatTensor([_TRAIN_START_TIME])
    torch.distributed.all_reduce(start_time_tensor,
                                 op=torch.distributed.ReduceOp.MIN)
    _TRAIN_START_TIME = start_time_tensor.item()
    print_rank_0('time to initialize megatron (seconds): {:.3f}'.format(
        time.time() - _TRAIN_START_TIME))
    print_datetime('after megatron is initialized')

    args = get_args()
    timers = get_timers()

    # Model, optimizer, and learning rate.
    timers('model and optimizer').start()
    model, optimizer, lr_scheduler = setup_model_and_optimizer(model_provider)
    timers('model and optimizer').stop()
    print_datetime('after model, optimizer, and learning rate '
                   'scheduler are built')

    # Data stuff.
    timers('train/valid/test data iterators').start()
    train_data_iterator, valid_data_iterator, test_data_iterator \
        = build_train_valid_test_data_iterators(
            train_valid_test_dataset_provider)
    timers('train/valid/test data iterators').stop()
    print_datetime('after dataloaders are built')

    # Print setup timing.
    print_rank_0('done with setups ...')
    timers.log(['model and optimizer', 'train/valid/test data iterators'])
    print_rank_0('training ...')

    iteration = 0
    if args.do_train and args.train_iters > 0:
        iteration = train(forward_step_func, model, optimizer, lr_scheduler,
                          train_data_iterator, valid_data_iterator)
    print_datetime('after training is done')

    if args.do_valid:
        prefix = 'the end of training for val data'
        evaluate_and_print_results(prefix, forward_step_func,
                                   valid_data_iterator, model, iteration,
                                   False)

    if args.save and iteration != 0:
        save_checkpoint(iteration, model, optimizer, lr_scheduler)

    if args.do_test:
        # Run on test data.
        prefix = 'the end of training for test data'
        evaluate_and_print_results(prefix, forward_step_func,
                                   test_data_iterator, model, 0, True)
Пример #9
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def main():

    # Arguments do sanity checks on the world size, but we don't care,
    # so trick it into thinking we are plenty of processes
    os.environ["WORLD_SIZE"] = f'{2**31}'

    # Args
    set_global_variables(extra_args_provider=get_mp_merge_args,
                         args_defaults={
                             'use_cpu_initialization': True,
                             'micro_batch_size': 1,
                             'no_load_optim': True,
                             'no_load_rng': True,
                             'no_save_optim': True,
                             'no_save_rng': True,
                             'save_interval': 1
                         })
    args = get_args()

    if args.pipeline_model_parallel_size > 1:
        print(
            "Checkpoints with pipeline model parallelism are not currently supported."
        )
        exit()

    model_type = args.model_type
    orig_tensor_model_parallel_size = args.tensor_model_parallel_size
    args.tensor_model_parallel_size = 1
    tokenizer = rebuild_tokenizer(args)

    print('\n merging model parallel partitions ...')
    print(
        ' > number of partitions: {}'.format(orig_tensor_model_parallel_size))
    print(' > checkpoint path: {}'.format(args.load))
    print(' > model parameters:')
    print('    number of tokens ................ {} '.format(
        tokenizer.vocab_size))
    print('    number of layers ................ {}'.format(args.num_layers))
    print('    hidden size ..................... {}'.format(args.hidden_size))
    print('    number of attention heads ....... {}'.format(
        args.num_attention_heads))
    print('    maximum position embeddings ..... {}'.format(
        args.max_position_embeddings))

    # Full model.
    print('> building the full model ...')
    mpu.initialize.set_tensor_model_parallel_world_size(1)
    mpu.initialize.set_tensor_model_parallel_rank(0)
    mpu.initialize.set_pipeline_model_parallel_world_size(1)
    mpu.initialize.set_pipeline_model_parallel_rank(0)
    merged_model = get_model(model_type)

    # Build and load partitions.
    partitions = []
    iteration = 0
    args.tensor_model_parallel_size = orig_tensor_model_parallel_size
    tokenizer = rebuild_tokenizer(args)
    mpu.initialize.set_tensor_model_parallel_world_size(
        args.tensor_model_parallel_size)
    for rank in range(args.tensor_model_parallel_size):
        # Reset these since load_checkpoint asserts they are 0, but we are loading
        # multiple checkpoints in the same process and they get set each time
        args.consumed_train_samples = 0
        args.consumed_valid_samples = 0

        mpu.initialize.set_tensor_model_parallel_rank(rank)
        checkpoint_name, iteration = get_parallel_checkpoint_name(args.load)
        model_ = get_model(model_type)
        print(f'> loading {checkpoint_name} ...')
        load_checkpoint(model_, None, None)
        print(f'> checkpoint version {get_checkpoint_version()}')
        partitions.append(model_)

    # Parameter generators so we can loop through them semiltaneouly.
    merged_params_gen = merged_model.named_parameters()
    partitions_params_gen = [
        partition.named_parameters() for partition in partitions
    ]
    while True:
        try:

            # Get the params and check names.
            name, merged_param = next(merged_params_gen)
            print(' > working on {} ...'.format(name))
            print('     merged         type: {}, size: {}'.format(
                merged_param.dtype, list(merged_param.size())))
            partitions_param = []
            for rank, partition_params_gen in enumerate(partitions_params_gen):
                partition_name, partition_param = next(partition_params_gen)
                assert partition_name == name
                partitions_param.append(partition_param)
                print('     partition {}    type: {}, size: {}'.format(
                    rank, partition_param.dtype, list(partition_param.size())))

            # For the non-parallel parameters, simply copy the rank 0 values.
            if not hasattr(merged_param, 'tensor_model_parallel'):
                print('     none-parallel parameter, simple copy from rank 0')
                with torch.no_grad():
                    merged_param.data.copy_(partitions_param[0].data)
            # For parallel parameters, merge the values
            else:
                dim = merged_param.partition_dim
                stride = merged_param.partition_stride
                print(
                    f'     parallel parameter merge with stride {stride} along '
                    f'dimention {dim}')
                merge_partitions(merged_param, partitions_param, dim, stride)

        except StopIteration:
            break

    partitions = []
    args.tensor_model_parallel_size = 1
    args.pipeline_model_parallel_size = args.target_pipeline_model_parallel_size

    assert args.num_layers % args.pipeline_model_parallel_size == 0, \
        'num_layers must be divisible by target pipeline model parallel size'
    layers_per_part = args.num_layers // args.pipeline_model_parallel_size

    tokenizer = rebuild_tokenizer(args)
    mpu.initialize.set_tensor_model_parallel_world_size(
        args.tensor_model_parallel_size)
    mpu.initialize.set_tensor_model_parallel_rank(0)
    mpu.initialize.set_pipeline_model_parallel_world_size(
        args.pipeline_model_parallel_size)

    # regex to parse out layer number from param name
    layer_re = re.compile('layers\.([0-9]+)')

    if args.pipeline_model_parallel_size > 1:
        merged_params = {}
        for name, merged_param in merged_model.named_parameters():
            merged_params[name] = merged_param

        for rank in range(args.pipeline_model_parallel_size):
            mpu.initialize.set_pipeline_model_parallel_rank(rank)
            model = get_model(model_type)

            def update_layer_num(m):
                # TODO! This assumes no interleaved pipeline execution
                layer = int(m.group(1))
                layer += rank * layers_per_part
                return f'layers.{layer}'

            for dst_name, partition_param in model.named_parameters():
                if dst_name == "word_embeddings.weight":
                    # See comment in MegatronModule.initialize_word_embeddings()
                    src_name = "language_model.embedding.word_embeddings.weight"
                else:
                    # Translate destination layer number (0-N for each partition)
                    # to source layer number (single-model layer number)
                    src_name = re.sub(layer_re, update_layer_num, dst_name)
                print(
                    f" > copying {src_name} to {dst_name} in rank {rank}'s model"
                )
                partition_param.data.copy_(merged_params[src_name].data)

            partitions.append(model)
    else:
        partitions = [merged_model]

    for rank, model in enumerate(partitions):
        mpu.initialize.set_pipeline_model_parallel_rank(rank)
        print(f"> saving rank {rank}'s model")
        save_checkpoint(iteration, model, None, None)

    print('done :-)')
Пример #10
0
def pretrain(neox_args):
    """Main training program.

    This function will run the following in the order provided:
        1) initialize Megatron.
        2) setup model, optimizer and lr schedule
        3) call train_val_test_data_provider to get train/val/test datasets.
        4) train the model.

    Arguments:
        neox_args: an instance of NeoXArgs containing the configuration for pretrain

    """
    # setup logging and timers
    init_wandb(neox_args=neox_args)
    timers = Timers(use_wandb=neox_args.use_wandb,
                    tensorboard_writer=neox_args.tensorboard_writer)

    # Initialize and get arguments, timers, and Tensorboard writer.
    initialize_megatron(neox_args=neox_args)

    # Model, optimizer, and learning rate.
    timers("model and optimizer").start()
    model, optimizer, lr_scheduler = setup_model_and_optimizer(
        neox_args=neox_args, use_cache=False)
    timers("model and optimizer").stop()

    # Data stuff.
    timers("train/valid/test data iterators").start()
    (
        train_data_iterator,
        valid_data_iterator,
        test_data_iterator,
    ) = build_train_valid_test_data_iterators(neox_args=neox_args)
    timers("train/valid/test data iterators").stop()

    # Print setup timing.
    print_rank_0("done with setups ...")
    timers.log(["model and optimizer", "train/valid/test data iterators"])
    print_rank_0("training ...")

    iteration = 0
    if neox_args.do_train and neox_args.train_iters > 0:
        iteration = train(
            neox_args=neox_args,
            timers=timers,
            model=model,
            optimizer=optimizer,
            lr_scheduler=lr_scheduler,
            train_data_iterator=train_data_iterator,
            valid_data_iterator=valid_data_iterator,
        )

    if neox_args.do_valid:
        prefix = "the end of training for val data"
        evaluate_and_print_results(
            neox_args=neox_args,
            prefix=prefix,
            forward_step_func=forward_step,
            data_iterator=valid_data_iterator,
            model=model,
            iteration=iteration,
            verbose=False,
            timers=timers,
        )

    if neox_args.save and iteration != 0:
        save_checkpoint(
            neox_args=neox_args,
            iteration=iteration,
            model=model,
            optimizer=optimizer,
            lr_scheduler=lr_scheduler,
        )

    if neox_args.do_test:
        # Run on test data.
        prefix = "the end of training for test data"
        evaluate_and_print_results(
            neox_args=neox_args,
            prefix=prefix,
            forward_step_func=forward_step,
            data_iterator=test_data_iterator,
            model=model,
            iteration=0,  # iteration 0 in order to always use full test data
            verbose=True,
            timers=timers,
        )
Пример #11
0
def train(
    neox_args,
    timers,
    model,
    optimizer,
    lr_scheduler,
    train_data_iterator,
    valid_data_iterator,
):
    """Train the model function."""

    # Turn on training mode which enables dropout.
    model.train()

    # Tracking loss.
    total_loss_dict = {}

    # Iterations.
    iteration = neox_args.iteration

    timers("interval time").start()
    report_memory_flag = True

    # get noise scale logger (if neox_args.log_gradient_noise_scale is True)
    noise_scale_logger = get_noise_scale_logger(neox_args)

    # to monitor if we've skipped many iterations in a row and trigger an early exit
    overflow_monitor = OverflowMonitor(optimizer)
    while iteration < neox_args.train_iters:
        loss_dict, skipped_iter = train_step(
            neox_args=neox_args,
            timers=timers,
            data_iterator=train_data_iterator,
            model=model,
            optimizer=optimizer,
            lr_scheduler=lr_scheduler,
        )
        iteration += 1

        overflow_monitor.check(skipped_iter)  # check for repeated overflow
        if neox_args.log_gradient_noise_scale:  # log noise scale if applicable
            noise_scale_logger.update()

        # get learning rate (if present) - if doing soft prompt tuning + pipe parallel, you
        # may have no tunable parameters on a specific rank
        if optimizer.param_groups:
            lr = optimizer.param_groups[0].get("lr", 0)
        else:
            lr = 0

        # Logging.
        report_memory_flag = training_log(
            neox_args=neox_args,
            timers=timers,
            loss_dict=loss_dict,
            total_loss_dict=total_loss_dict,
            learning_rate=lr,
            iteration=iteration,
            loss_scale=optimizer.cur_scale
            if neox_args.precision == "fp16" else None,
            report_memory_flag=report_memory_flag,
            skipped_iter=skipped_iter,
            model=model,
            optimizer=optimizer,
            noise_scale_logger=noise_scale_logger,
        )

        # Checkpointing
        if (neox_args.save and neox_args.save_interval
                and iteration % neox_args.save_interval == 0):
            save_checkpoint(
                neox_args=neox_args,
                iteration=iteration,
                model=model,
                optimizer=optimizer,
                lr_scheduler=lr_scheduler,
            )

        # Evaluation
        if (neox_args.eval_interval
                and iteration % neox_args.eval_interval == 0
                and neox_args.do_valid):
            prefix = "iteration {}".format(iteration)
            evaluate_and_print_results(
                neox_args=neox_args,
                prefix=prefix,
                forward_step_func=forward_step,
                data_iterator=valid_data_iterator,
                model=model,
                iteration=iteration,
                verbose=False,
                timers=timers,
            )

        if neox_args.exit_interval and iteration % neox_args.exit_interval == 0:
            torch.distributed.barrier()
            time_str = datetime.now().strftime("%Y-%m-%d %H:%M:%S")
            rank = torch.distributed.get_rank()
            print_rank_0(
                "rank: {} | time: {} | exiting the program at iteration {}".
                format(rank, time_str, iteration))
            sys.exit()

    return iteration
Пример #12
0
def _train(model, optimizer, lr_scheduler, forward_step, train_dataloader,
           valid_dataloader, end_of_epoch_callback):
    """Train the model."""
    args = get_args()
    timers = get_timers()

    assert get_num_microbatches(
    ) == 1, "finetuning with gradient accumulation doesn't currently work"

    # Turn on training mode which enables dropout.
    for m in model:
        m.train()

    # Tracking loss.
    losses_dict_sum = {}

    # Starting epoch and iteration
    start_epoch = args.iteration // args.train_iters_per_epoch
    start_iteration = args.iteration % args.train_iters_per_epoch
    iteration = args.iteration

    # Memory reporting flag.
    report_memory_flag = True

    # For each remaining epoch
    timers('interval-time').start()
    for epoch in range(start_epoch, args.epochs):
        print_rank_0('working on epoch {} ...'.format(epoch + 1))

        # Set the data loader epoch to shuffle the index iterator.
        train_dataloader.sampler.set_epoch(args.seed + epoch)

        # For all the batches in the dataset.
        for iteration_, batch in enumerate(train_dataloader):

            # Ignore the iterations before starting value
            if iteration_ < start_iteration:
                continue
            # Set to zero so the next epoch does not skip any batches.
            start_iteration = 0

            # Train for one step.
            out = train_step(forward_step, batch, model, optimizer,
                             lr_scheduler)

            losses_dict, skipped_iter, grad_norm, num_zeros_in_grad = out
            iteration += 1

            # Logging.
            params_norm = None
            if args.log_params_norm:
                params_norm = calc_params_l2_norm(model)
            report_memory_flag = training_log(
                losses_dict, losses_dict_sum, optimizer.param_groups[0]['lr'],
                iteration,
                optimizer.get_loss_scale().item(), report_memory_flag,
                skipped_iter, grad_norm, params_norm, num_zeros_in_grad)

            # Autoresume
            if args.adlr_autoresume and \
               (iteration % args.adlr_autoresume_interval == 0):
                check_adlr_autoresume_termination(iteration, model, optimizer,
                                                  lr_scheduler)

            # Checkpointing
            saved_checkpoint = False
            if args.save and args.save_interval and \
               iteration % args.save_interval == 0:
                save_checkpoint(iteration, model, optimizer, lr_scheduler)
                saved_checkpoint = True

            # Evaluation
            if args.eval_interval and iteration % args.eval_interval == 0:
                prefix = 'iteration {}'.format(iteration)
                evaluate_and_print_results(prefix, forward_step,
                                           valid_dataloader, model, iteration,
                                           False)

            # Exiting based on iterations
            if args.exit_interval and iteration % args.exit_interval == 0:
                if not saved_checkpoint:
                    save_checkpoint(iteration, model, optimizer, lr_scheduler)
                torch.distributed.barrier()
                print_rank_0(
                    'exiting program at iteration {}'.format(iteration))
                sys.exit()

        # Checkpointing at the end of each epoch.
        if args.save:
            save_checkpoint(iteration, model, optimizer, lr_scheduler)

        # Callback at the end of each epoch.
        if end_of_epoch_callback is not None:
            end_of_epoch_callback(model, epoch)