Function gradient

dask/array/routines.py:661–735

(f, *varargs, axis=None, **kwargs)

@derived_from(np)
def gradient(f, *varargs, axis=None, **kwargs):
    f = asarray(f)

    kwargs["edge_order"] = math.ceil(kwargs.get("edge_order", 1))
    if kwargs["edge_order"] > 2:
        raise ValueError("edge_order must be less than or equal to 2.")

    drop_result_list = False
    if axis is None:
        axis = tuple(range(f.ndim))
    elif isinstance(axis, Integral):
        drop_result_list = True
        axis = (axis,)

    axis = validate_axis(axis, f.ndim)

    if len(axis) != len(set(axis)):
        raise ValueError("duplicate axes not allowed")

    axis = tuple(ax % f.ndim for ax in axis)

    if varargs == ():
        varargs = (1,)
    if len(varargs) == 1:
        varargs = len(axis) * varargs
    if len(varargs) != len(axis):
        raise TypeError(
            "Spacing must either be a single scalar, or a scalar / 1d-array per axis"
        )

    if issubclass(f.dtype.type, (np.bool_, Integral)):
        f = f.astype(float)
    elif issubclass(f.dtype.type, Real) and f.dtype.itemsize < 4:
        f = f.astype(float)

    results = []
    for i, ax in enumerate(axis):
        for c in f.chunks[ax]:
            if np.min(c) < kwargs["edge_order"] + 1:
                raise ValueError(
                    "Chunk size must be larger than edge_order + 1. "
                    f"Minimum chunk for axis {ax} is {np.min(c)}. Rechunk to "
                    "proceed."
                )

        if np.isscalar(varargs[i]):
            array_locs = None
        else:
            if isinstance(varargs[i], Array):
                raise NotImplementedError("dask array coordinated is not supported.")
            # coordinate position for each block taking overlap into account
            chunk = np.array(f.chunks[ax])
            array_loc_stop = np.cumsum(chunk) + 1
            array_loc_start = array_loc_stop - chunk - 2
            array_loc_stop[-1] -= 1
            array_loc_start[0] = 0
            array_locs = (array_loc_start, array_loc_stop)