import asyncio
import collections
import time

def measure_accuracy_cb(fut, t0):
    dt = time.perf_counter() - t0
    fut.set_result(dt)

@asyncio.coroutine
def measure_accuracy(deltas, nruns=10):
    for run in range(1, nruns+1):
        for unit, format, multiply in (
            (1,    "%.3f ms", 1e3),     # seconds
            (1e-1, "%.1f ms", 1e3),   # milliseconds
            (1e-2, "%.1f ms", 1e3),   # milliseconds
            (1e-3, "%.1f ms", 1e3),   # milliseconds
            (1e-4, "%.1f us", 1e6),   # milliseconds
            (1e-6, "%.1f us", 1e6),   # microsecond
            (1e-9, "%.4f us", 1e6),   # microsecond
        ):
            for factor in (0.1, 0.5, 1.0, 1.5, 2.0, 3.0, 4.0, 5.0):
                fut = asyncio.Future()
                delay = unit * factor
                print("Test %s (run #%s/%s)" % (delay, run, nruns))
                t0 = time.perf_counter()
                loop.call_later(delay, measure_accuracy_cb, fut, t0)
                yield from asyncio.wait_for(fut, None)
                dt = fut.result() - delay
                deltas[(delay, format, multiply)].append(dt)

loop = asyncio.get_event_loop()
deltas = collections.defaultdict(list)
loop.run_until_complete(measure_accuracy(deltas))
print("")
print("[ asyncio accuracy ]")
all_dt = []
for key, dt in sorted(deltas.items()):
    delay, format, multiply = key
    dt_min = min(dt)
    dt_max = max(dt)
    percent_min = dt_min * 100. / delay
    percent_max = dt_max * 100. / delay
    delay = format % (delay * multiply)
    dt_min = format % (dt_min * multiply)
    dt_max = format % (dt_max * multiply)
    print("call_later(%s): difference in [%s; %s], [%+.1f%%, %+.1f%%]"
          % (delay, dt_min, dt_max, percent_min, percent_max))
    all_dt.extend(dt)

dt_min = min(all_dt)
dt_max = max(all_dt)
print("Global accuracy in [%.1f us; %.1f ms]"
      % (dt_min * 1e6, dt_max * 1e3))
print("")
if hasattr(loop, '_granularity'):
    print("Loop granularity: %.1f ms" % (loop._granularity * 1e3))
if hasattr(loop._selector, 'resolution'):
    print("Selector resolution: %.1f ms" % (loop._selector.resolution * 1e3))
print("Event loop: %s" % loop.__class__.__name__)
print("Selector: %s" % loop._selector.__class__.__name__)

loop.close()