Method compute_chunk_sizes

dask/array/core.py:1465–1512

Compute the chunk sizes for a Dask array. This is especially useful when the chunk sizes are unknown (e.g., when indexing one Dask array with another). Notes ----- This function modifies the Dask array in-place. Examples --------

(self)

        return reduce(mul, self.numblocks, 1)

    def compute_chunk_sizes(self):
        """
        Compute the chunk sizes for a Dask array. This is especially useful
        when the chunk sizes are unknown (e.g., when indexing one Dask array
        with another).

        Notes
        -----
        This function modifies the Dask array in-place.

        Examples
        --------
        >>> import dask.array as da
        >>> import numpy as np
        >>> x = da.from_array([-2, -1, 0, 1, 2], chunks=2)
        >>> x.chunks
        ((2, 2, 1),)
        >>> y = x[x <= 0]
        >>> y.chunks
        ((nan, nan, nan),)
        >>> y.compute_chunk_sizes()  # in-place computation
        dask.array<getitem, shape=(3,), dtype=int64, chunksize=(2,), chunktype=numpy.ndarray>
        >>> y.chunks
        ((2, 1, 0),)

        """
        x = self
        chunk_shapes = x.map_blocks(
            _get_chunk_shape,
            dtype=int,
            chunks=tuple(len(c) * (1,) for c in x.chunks) + ((x.ndim,),),
            new_axis=x.ndim,
        )

        c = []
        for i in range(x.ndim):
            s = x.ndim * [0] + [i]
            s[i] = slice(None)
            s = tuple(s)

            c.append(tuple(chunk_shapes[s]))

        # `map_blocks` assigns numpy dtypes
        # cast chunk dimensions back to python int before returning
        x._chunks = tuple(
            tuple(int(chunk) for chunk in chunks) for chunks in compute(tuple(c))[0]
        )
        return x

    @cached_property
    def shape(self) -> tuple[T_IntOrNaN, ...]: