How to find nearest divisor to given value with modulo zero

Question

I'm trying to preprocess a dataset for a neuronal network. Therefore, I need to reshape an array with the shape (2040906, 1) into an array of batches.

I need a batch size around 1440 rows but 2040906 is not dividable (with a remainder of zero) by that number obviously.

I tried to just calculate the modulo of the division and drop as many rows as the remainder so the division will result in a modulo of zero. But dropping rows of my dataset is not what I want to do.

So this is an example snippet to reproduce the problem.

import numpy as np

x = np.ones((2040906, 1))

np.split(x, 1440)

The perfect solution for me would be some kind of function, that returns the nearest divisor for a given value that has a remainder of 0.

Answer 1

Not sure this is the most elegant solution, but you can do the following:

1. Get all divisor for the number in question

def getDivisors(n, res=None) : 
    res = res or []
    i = 1
    while i <= n : 
        if (n % i==0) : 
            res.append(i), 
        i = i + 1
    return res

getDivisors(2040906)
Out[4]: 
[1,
 2,
 3,
 6,
 7,
 14,
 21,
 42,
 48593,
 97186,
 145779,
 291558,
 340151,
 680302,
 1020453,
 2040906]

2. Return the closest divisor

def get_closest_split(n, close_to=1440):
    all_divisors = getDivisors(n)
    for ix, val in enumerate(all_divisors):
        if close_to < val:
            if ix == 0: return val
            if (val-close_to)>(close_to - all_divisors[ix-1]):
                return all_divisors[ix-1]
            return val

def get_closest_split(n, close_to=1440)
Out[6]: 42

Which in your case, would return 42 as the only divisor closest to 1440. Thus, np.split(x, 42) should work.