import subprocess, sys
from time import time

RUNS = 5
LOOPS = 100
ARGS = [sys.executable, '-c', 'pass']

def bench(env):
    best = None
    for run in range(RUNS):
        print("%s/%s" % (run, RUNS))
        a = time()
        for loop in range(LOOPS):
            subprocess.call(ARGS, env=env)
        b = time()
        dt = float(b - a) / LOOPS
        if best is not None:
            best = min(best, dt)
        else:
            best = dt
    return best

a = bench(None)
b = bench({'PYTHONHASHSEED': '0'})
a *= 1000
b *= 1000
print("%.1f ms (random) vs %.1f ms (const)" % (a, b))
dt = a - b
print("Overhead: %.1f ms (%.0f%%)" % (dt, dt * 100. / b))