def __call__()

in src/nanotron/data/clm_collator.py [0:0]


    def __call__(self, examples: List[Dict[str, List[np.ndarray]]]) -> Dict[str, Union[torch.Tensor, TensorPointer]]:

        vstack = np.vstack if self.use_numpy else torch.vstack
        ones = np.ones if self.use_numpy else torch.ones
        bool_dtype = np.bool_ if self.use_numpy else torch.bool

        # Process the case when current rank doesn't require data. We return `TensorPointer` that points to ranks having the data.
        current_pp_rank = dist.get_rank(self.parallel_context.pp_pg)
        if current_pp_rank not in [
            self.input_pp_rank,
            self.output_pp_rank,
        ]:
            assert all(len(example) == 0 for example in examples)
            return {
                "input_ids": TensorPointer(group_rank=self.input_pp_rank),
                "input_mask": TensorPointer(group_rank=self.input_pp_rank),
                "label_ids": TensorPointer(group_rank=self.output_pp_rank),
                "label_mask": TensorPointer(group_rank=self.output_pp_rank),
            }

        # TODO @nouamanetazi: Is it better to have examples as np.array or torch.Tensor?
        input_ids = vstack([examples[i]["input_ids"] for i in range(len(examples))])  # (b, s)
        batch_size, expanded_input_length = input_ids.shape

        result: Dict[str, Union[np.ndarray, torch.LongTensor, TensorPointer]] = {}

        result["input_ids"] = TensorPointer(group_rank=self.input_pp_rank)
        result["input_mask"] = TensorPointer(group_rank=self.input_pp_rank)
        result["label_ids"] = TensorPointer(group_rank=self.output_pp_rank)
        result["label_mask"] = TensorPointer(group_rank=self.output_pp_rank)

        assert (
            expanded_input_length == self.sequence_length + 1
        ), f"Samples should be of length {self.sequence_length + 1} (seq_len+1), but got {expanded_input_length}"

        # Process inputs: last token is the label
        if current_pp_rank == self.input_pp_rank:
            result["input_ids"] = input_ids[:, :-1]
            result["input_mask"] = ones((batch_size, self.sequence_length), dtype=bool_dtype)

            # Context Parallelism: Each CP rank gets a slice of the input_ids and input_mask
            cp_rank, cp_size = dist.get_rank(self.parallel_context.cp_pg), self.parallel_context.context_parallel_size
            local_slice = slice(
                cp_rank * self.sequence_length // cp_size, (cp_rank + 1) * self.sequence_length // cp_size
            )
            result["input_ids"] = result["input_ids"][:, local_slice]  # (b, s/cp_size)
            result["input_mask"] = result["input_mask"][:, local_slice]  # (b, s/cp_size)

        # Process labels: shift them to the left
        if current_pp_rank == self.output_pp_rank:
            result["label_ids"] = input_ids[:, 1:]

            # Create label mask based on position_ids
            if "positions" in examples[0]:
                # Get position_ids for the labels (shifted right by 1 to align with label_ids)
                position_ids = np.vstack([examples[i]["positions"] for i in range(len(examples))])
                position_ids = position_ids[:, 1:]  # Shift right to align with labels

                # Create mask: True for all tokens except the one before position_id == 0
                result["label_mask"] = np.ones((batch_size, self.sequence_length), dtype=np.bool_)

                # Find where position_ids is 0
                zeros = position_ids == 0
                # Mask the current token where we found zeros (since labels are already shifted right)
                result["label_mask"] &= ~zeros
            else:
                # Default: all tokens are used for loss
                result["label_mask"] = np.ones((batch_size, self.sequence_length), dtype=np.bool_)

            # Context Parallelism: Each CP rank gets a slice of the label_ids and label_mask
            cp_rank, cp_size = dist.get_rank(self.parallel_context.cp_pg), self.parallel_context.context_parallel_size
            local_slice = slice(
                cp_rank * self.sequence_length // cp_size, (cp_rank + 1) * self.sequence_length // cp_size
            )
            result["label_ids"] = result["label_ids"][:, local_slice]  # (b, s/cp_size)
            result["label_mask"] = result["label_mask"][:, local_slice]  # (b, s/cp_size)

        if (
            not isinstance(result["input_ids"], TensorPointer)
            and result["input_ids"].shape[-1] != self.sequence_length // cp_size
        ):
            raise ValueError(
                f"`labels` are incorrectly preprocessed. `labels` length is {result['input_ids'].shape[-1]}, but should be"
                f" {self.sequence_length // cp_size}."
            )
        if (
            not isinstance(result["label_ids"], TensorPointer)
            and result["label_ids"].shape[-1] != self.sequence_length // cp_size
        ):
            raise ValueError(
                f"`labels` are incorrectly preprocessed. `labels` length is {result['label_ids'].shape[-1]}, but should be"
                f" {self.sequence_length // cp_size}."
            )

        # # Maybe cast np.array to torch.Tensor
        # result = {
        #     k: v if isinstance(v, TensorPointer) else (torch.from_numpy(v).contiguous() if self.use_numpy else v)
        #     for k, v in result.items()
        # }  # TODO: @nouamane in case of memory issues, try keeping numpy here.
        # # assert contiguous
        # for k, v in result.items():
        #     if not isinstance(v, TensorPointer):
        #         assert v.is_contiguous(), f"{k} is not contiguous"
        #         assert not v.is_cuda, f"{k} is in cuda. Bad for pinning memory"
        return result