rasterio read speed test helper function

riotest.py

import rasterio as rio
import concurrent.futures as cf

def fc(p,n=4):
    with rio.open(p) as src:
        blocks = [_[1] for _ in src.block_windows()]
    def rf(w):
        with rio.open(p) as src:
            data=src.read(window=w)
        return data
    with cf.ThreadPoolExecutor(max_workers=n) as ex:
        x = list(ex.map(rf, blocks))