# dask only version of this problem

shape = (100000, 100, 200)
chunks = (50, 100, 200)
data = dsa.random.random(shape, chunks=chunks)
data

data_rc = data.rechunk((1000, 1, 200))
data_rc

da.data.ravel

from time import sleep

def my_custom_function(f):
    # do some computations
    g = f**2 + 2*np.sin(f)
    sleep(0.01)
    # and reduce shape
    return g.ravel()[::15]

data_rc.map_blocks(my_custom_function, drop_axis=[1, 2], new_axis=[1], chunks=(1, 15))