# Copyright (c) Microsoft Corporation.
# Licensed under the MIT license.

"""Module of the Pytorch GPT2 model."""

import torch
from transformers import GPT2Model, GPT2Config
try:
    import transformer_engine.pytorch as te
    from transformer_engine.common.recipe import Format, DelayedScaling
except ImportError:
    te = None

from superbench.common.utils import logger
from superbench.benchmarks import BenchmarkRegistry, Precision
from superbench.benchmarks.model_benchmarks.model_base import Optimizer
from superbench.benchmarks.model_benchmarks.pytorch_base import PytorchBase
from superbench.benchmarks.model_benchmarks.random_dataset import TorchRandomDataset


class GPT2BenchmarkModel(torch.nn.Module):
    """The GPT2 model for benchmarking."""
    def __init__(self, config, num_classes):
        """Constructor.

        Args:
            config (GPT2Config): Configurations of GPT2 model.
            num_classes (int): The number of objects for classification.
        """
        super().__init__()
        self._gpt2 = GPT2Model(config)
        self._linear = torch.nn.Linear(config.hidden_size, num_classes)

    def forward(self, input):
        """Forward propagation function.

        Args:
            input (torch.LongTensor): Indices of input sequence tokens in the vocabulary,
                shape (batch_size, sequence_length).

        Return:
            result (torch.FloatTensor): Last layer hidden-state of the first token of the sequence
              (classification token) further processed by a Linear layer, shape (batch_size, hidden_size).
        """
        outputs = self._gpt2(input)
        result = self._linear(outputs[0])
        return result


class PytorchGPT2(PytorchBase):
    """The GPT2 benchmark class."""
    def __init__(self, name, parameters=''):
        """Constructor.

        Args:
            name (str): benchmark name.
            parameters (str): benchmark parameters.
        """
        super().__init__(name, parameters)
        self._config = None
        self._fp8_recipe = None
        self._supported_precision = [
            Precision.FLOAT32,
            Precision.FLOAT16,
            Precision.FP8_HYBRID,
            Precision.FP8_E4M3,
        ]
        self._optimizer_type = Optimizer.ADAMW
        self._loss_fn = torch.nn.CrossEntropyLoss()

    def add_parser_arguments(self):
        """Add the GPT2-specified arguments.

        GPT2 model reference: https://huggingface.co/docs/transformers/model_doc/gpt2
        """
        super().add_parser_arguments()

        self._parser.add_argument('--num_classes', type=int, default=100, required=False, help='Num of class.')
        self._parser.add_argument('--hidden_size', type=int, default=1280, required=False, help='Hidden size.')
        self._parser.add_argument(
            '--num_hidden_layers', type=int, default=36, required=False, help='The number of hidden layers.'
        )
        self._parser.add_argument(
            '--num_attention_heads', type=int, default=20, required=False, help='The number of attention heads.'
        )
        self._parser.add_argument('--seq_len', type=int, default=512, required=False, help='Sequence length.')

    def _generate_dataset(self):
        """Generate dataset for benchmarking according to shape info.

        Return:
            True if dataset is created successfully.
        """
        self._dataset = TorchRandomDataset(
            [self._args.sample_count, self._args.seq_len], self._world_size, dtype=torch.long
        )
        if len(self._dataset) == 0:
            logger.error('Generate random dataset failed - model: {}'.format(self._name))
            return False

        return True

    def _create_model(self, precision):
        """Construct the model for benchmarking.

        Args:
            precision (Precision): precision of model and input data, such as float32, float16.
        """
        self._config = GPT2Config(
            n_embd=self._args.hidden_size, n_layer=self._args.num_hidden_layers, n_head=self._args.num_attention_heads
        )

        enable_fp8 = precision.name.startswith('FP8_')
        if enable_fp8 and te is None:
            logger.error(
                f'Create model with fp8 failed - model: {self._name}, precision: {precision},'
                ' message: Cannot find transformer_engine.'
            )
            return False
        if enable_fp8 and not self._gpu_available:
            logger.error(
                f'Create model with fp8 failed - model: {self._name}, precision: {precision},'
                ' message: FP8 is only supported on GPU.'
            )
            return False

        try:
            self._model = GPT2BenchmarkModel(self._config, self._args.num_classes)
            if enable_fp8:
                self._fp8_recipe = DelayedScaling(
                    fp8_format=Format[precision.name.strip('FP8_')],
                    amax_history_len=16,
                    amax_compute_algo='max',
                )
                self._to_te_model(self._model.to(dtype=torch.float16))
            else:
                self._model = self._model.to(dtype=getattr(torch, precision.value))
            if self._gpu_available:
                self._model = self._model.cuda()
        except BaseException as e:
            logger.error(
                'Create model with specified precision failed - model: {}, precision: {}, message: {}.'.format(
                    self._name, precision, str(e)
                )
            )
            return False

        self._target = self._create_target(self._args.num_classes)

        return True

    def _train_step(self, precision):
        """Define the training process.

        Args:
            precision (Precision): precision of model and input data, such as float32, float16.

        Return:
            A tuple of (step_times_ms, info) of every training step.
        """
        duration = []
        periodic = {'loss': [], 'act_mean': [], 'step': []}
        curr_step = 0
        while True:
            for idx, sample in enumerate(self._dataloader):
                start = self._timer()
                if self._gpu_available:
                    sample = sample.cuda()
                if self._args.exclude_copy_time:
                    start = self._timer()
                self._optimizer.zero_grad()
                if self._fp8_recipe is not None:
                    with te.fp8_autocast(enabled=True, fp8_recipe=self._fp8_recipe):
                        output = self._model(sample)
                else:
                    output = self._model(sample)
                logits = output[range(self._args.batch_size), -1]
                # Use FP32 logits for loss only when determinism is enabled; otherwise
                # keep logits in their native precision to preserve benchmark semantics.
                enable_determinism = getattr(self._args, 'enable_determinism', False)
                logits_for_loss = logits.float() if enable_determinism else logits
                loss = self._loss_fn(logits_for_loss, self._target)
                loss.backward()
                self._optimizer.step()
                end = self._timer()
                curr_step += 1
                if curr_step > self._args.num_warmup:
                    # Save the step time of every training/inference step, unit is millisecond.
                    duration.append((end - start) * 1000)
                    self.record_determinism_fingerprint(curr_step, loss, logits, periodic, self._args.check_frequency)
                    self._log_step_time(curr_step, precision, duration)
                if self._is_finished(curr_step, end, self._args.check_frequency):
                    return duration, self._finalize_periodic_logging(periodic)

    def _inference_step(self, precision):
        """Define the inference process.

        Args:
            precision (Precision): precision of model and input data,
              such as float32, float16.

        Return:
            The latency list of every inference operation.
        """
        duration = []
        curr_step = 0
        with torch.no_grad():
            self._model.eval()
            while True:
                for idx, sample in enumerate(self._dataloader):
                    start = self._timer()
                    if self._gpu_available:
                        sample = sample.cuda()
                    if self._args.exclude_copy_time:
                        start = self._timer()
                    if self._fp8_recipe is not None:
                        with te.fp8_autocast(enabled=True, fp8_recipe=self._fp8_recipe):
                            self._model(sample)
                    else:
                        self._model(sample)
                    end = self._timer()
                    curr_step += 1
                    if curr_step > self._args.num_warmup:
                        # Save the step time of every training/inference step, unit is millisecond.
                        duration.append((end - start) * 1000)
                        self._log_step_time(curr_step, precision, duration)
                    if self._is_finished(curr_step, end, self._args.check_frequency):
                        return duration


# Register GPT2 benchmark with 117M parameters.
# Reference: https://huggingface.co/transformers/v3.3.1/pretrained_models.html
BenchmarkRegistry.register_benchmark(
    'pytorch-gpt2-small', PytorchGPT2, parameters='--hidden_size=768 --num_hidden_layers=12 --num_attention_heads=12'
)

# Register GPT2 benchmark with 345M parameters.
# Reference: https://huggingface.co/transformers/v3.3.1/pretrained_models.html
BenchmarkRegistry.register_benchmark(
    'pytorch-gpt2-medium', PytorchGPT2, parameters='--hidden_size=1024 --num_hidden_layers=24 --num_attention_heads=16'
)

# Register GPT2 benchmark with 774M parameters.
# Reference: https://huggingface.co/transformers/v3.3.1/pretrained_models.html
BenchmarkRegistry.register_benchmark(
    'pytorch-gpt2-large', PytorchGPT2, parameters='--hidden_size=1280 --num_hidden_layers=36 --num_attention_heads=20'
)

# Register GPT2 benchmark with 1558M parameters.
# Reference: https://huggingface.co/transformers/v3.3.1/pretrained_models.html
BenchmarkRegistry.register_benchmark(
    'pytorch-gpt2-xl', PytorchGPT2, parameters='--hidden_size=1600 --num_hidden_layers=48 --num_attention_heads=25'
)
