Function rechunk

dask/array/rechunk.py:270–390

Convert blocks in dask array x for new chunks. Parameters ---------- x: dask array Array to be rechunked. chunks: int, tuple, dict or str, optional The new block dimensions to create. -1 indicates the full size of the corresponding dimension. Default is

(
    x,
    chunks="auto",
    threshold=None,
    block_size_limit=None,
    balance=False,
    method=None,
)

def rechunk(
    x,
    chunks="auto",
    threshold=None,
    block_size_limit=None,
    balance=False,
    method=None,
):
    """
    Convert blocks in dask array x for new chunks.

    Parameters
    ----------
    x: dask array
        Array to be rechunked.
    chunks:  int, tuple, dict or str, optional
        The new block dimensions to create. -1 indicates the full size of the
        corresponding dimension. Default is "auto" which automatically
        determines chunk sizes.
    threshold: int, optional
        The graph growth factor under which we don't bother introducing an
        intermediate step.
    block_size_limit: int, optional
        The maximum block size (in bytes) we want to produce
        Defaults to the configuration value ``array.chunk-size``
    balance : bool, default False
        If True, try to make each chunk to be the same size.

        This means ``balance=True`` will remove any small leftover chunks, so
        using ``x.rechunk(chunks=len(x) // N, balance=True)``
        will almost certainly result in ``N`` chunks.
    method: {'tasks', 'p2p'}, optional.
        Rechunking method to use.


    Examples
    --------
    >>> import dask.array as da
    >>> x = da.ones((1000, 1000), chunks=(100, 100))

    Specify uniform chunk sizes with a tuple

    >>> y = x.rechunk((1000, 10))

    Or chunk only specific dimensions with a dictionary

    >>> y = x.rechunk({0: 1000})

    Use the value ``-1`` to specify that you want a single chunk along a
    dimension or the value ``"auto"`` to specify that dask can freely rechunk a
    dimension to attain blocks of a uniform block size

    >>> y = x.rechunk({0: -1, 1: 'auto'}, block_size_limit=1e8)

    If a chunk size does not divide the dimension then rechunk will leave any
    unevenness to the last chunk.

    >>> x.rechunk(chunks=(400, -1)).chunks