円周率

circle_ratio.py

import numpy as np
import pandas as pd


def main(args):
    np.random.seed(args.seed)

    index = []
    history = []
    n_within_circle = 0
    for i in range(args.iter):
        sample = 2.0 * np.random.random(2) - 1.0
        if sample.dot(sample) < 1.0:
            n_within_circle += 1

        total = i + 1

        if (total * 10) % args.interval == 0:
            assumed_pi = 4 * n_within_circle / total
            index.append(total)
            history.append(assumed_pi)
            if total % args.interval == 0:
                print("{}/{} assumed_pi={}".format(
                    n_within_circle, total, assumed_pi))

    ax = pd.DataFrame(history, index=index).plot(
        ylim=[3, 3.3], legend=False, logx=True)
    fig = ax.get_figure()
    fig.savefig(args.out)


def get_parser():
    import argparse
    parser = argparse.ArgumentParser()
    parser.add_argument("--iter", default=1000000, type=int)
    parser.add_argument("--interval", default=10000, type=int)
    parser.add_argument("--seed", default=13, type=int)
    parser.add_argument("--out", default="pi_history.png")
    return parser


if __name__ == '__main__':
    main(get_parser().parse_args())