#!/usr/bin/env python
# -*- coding: utf-8 -*-
# written by Christoph Federrath, 2019

# define imports
import argparse
import numpy as np
import timeit


# ===== the following applies in case we are running this in script mode =====
if __name__ == "__main__":

    parser = argparse.ArgumentParser(description='Sum numbers from 1 to n.')
    parser.add_argument("-n", "--n", type=float, help="Number n", default=5e6)

    args = parser.parse_args()

    # cast float n to int
    int_n = int(args.n)

    # print
    print("Summing all integers from 1 to "+str(int_n)+"...")
    
    # define array with numbers (for np.sum() below)
    numbers = np.arange(int_n)+1
    
    # start the timer
    start_time = timeit.default_timer()

    # sum up numbers 1 to n using a loop
    #sum = 0.0
    #for i in range(1, int_n+1):
    #    sum += i

    # sum up with numpy.sum()
    sum = np.sum(numbers)
        
    # stop the timer
    end_time = timeit.default_timer()
        
    # print the sum to stdout
    print("Sum = "+str(sum))

    # print the time it took
    print("Run time = "+str(end_time-start_time)+" s")