Function broadcast_to

dask/array/core.py:5106–5178

Broadcast an array to a new shape. Parameters ---------- x : array_like The array to broadcast. shape : tuple The shape of the desired array. chunks : tuple, optional If provided, then the result will use these chunks instead of the same chunks as

(x, shape, chunks=None, meta=None)

def broadcast_to(x, shape, chunks=None, meta=None):
    """Broadcast an array to a new shape.

    Parameters
    ----------
    x : array_like
        The array to broadcast.
    shape : tuple
        The shape of the desired array.
    chunks : tuple, optional
        If provided, then the result will use these chunks instead of the same
        chunks as the source array. Setting chunks explicitly as part of
        broadcast_to is more efficient than rechunking afterwards. Chunks are
        only allowed to differ from the original shape along dimensions that
        are new on the result or have size 1 the input array.
    meta : empty ndarray
        empty ndarray created with same NumPy backend, ndim and dtype as the
        Dask Array being created (overrides dtype)

    Returns
    -------
    broadcast : dask array

    See Also
    --------
    :func:`numpy.broadcast_to`
    """
    x = asarray(x)
    shape = tuple(shape)

    if meta is None:
        meta = meta_from_array(x)

    if x.shape == shape and (chunks is None or chunks == x.chunks):
        return x

    ndim_new = len(shape) - x.ndim
    if ndim_new < 0 or any(
        new != old for new, old in zip(shape[ndim_new:], x.shape) if old != 1
    ):
        raise ValueError(f"cannot broadcast shape {x.shape} to shape {shape}")

    if chunks is None:
        chunks = tuple((s,) for s in shape[:ndim_new]) + tuple(
            bd if old > 1 else (new,)
            for bd, old, new in zip(x.chunks, x.shape, shape[ndim_new:])
        )
    else:
        chunks = normalize_chunks(
            chunks, shape, dtype=x.dtype, previous_chunks=x.chunks
        )
        for old_bd, new_bd in zip(x.chunks, chunks[ndim_new:]):
            if old_bd != new_bd and old_bd != (1,):
                raise ValueError(
                    "cannot broadcast chunks %s to chunks %s: "
                    "new chunks must either be along a new "
                    "dimension or a dimension of size 1" % (x.chunks, chunks)
                )