#!/urs/bin/env python3
"""
sum_values.py
This program has a sum_values(n) function that adds up the integers from
1 to n and returns that value. 
The main function runs through a series of tests of that function, with
increasingly large values of n. The time it takes for each of those additions
to occur is captured. The results of these tests are then written to an
external CSV file.
That CSV file can be imported into a spreadsheet program and analyzed with
a trend line.

@author Richard White
@version 2018-02-14
"""

import time

def sum_values(n):
    """Sums the values from 1 to n, inclusive
    """
    sums = 0
    for i in range(1,n+1):
        sums += i
    return sums

def main():
    LOWER = 1000000
    UPPER = 10000000
    INTERVAL = 1000000
    outfile = open('result.csv','w')
    for val in range(LOWER, UPPER, INTERVAL):
        time_initial = time.time()              # test starts
        result = sum_values(val)                # call function
        time_final = time.time()                # test is completed
        print(val, time_final - time_initial)   # prints on screen
        # writes results out to file
        outfile.write(str(val) + ',' + str(time_final - time_initial) + "\n")  
    outfile.close()
    print("Results written out to result.csv")


if __name__ == "__main__":
    main()