rounder.py

import numpy as np
"""
For details, see 

[1] https://people.eecs.berkeley.edu/~wkahan/ieee754status/IEEE754.PDF
[2] https://docs.scipy.org/doc/numpy/reference/generated/numpy.around.html?highlight=round#numpy.around

Thanks to fesetround from ctypes. We can  manually set the rounding mode
"""
import ctypes, sys
ROUND_TONEAREST = 0x0000
ROUND_DOWNWARD = 0x0400
ROUND_UPWARD = 0x0800
ROUND_TOWARDZERO = 0x0c00
if (sys.platform).lower() == 'darwin': # MAC
    libc = ctypes.CDLL('libc.dylib')
elif sys.platform.lower() == 'linux': # Linux
    libc = ctypes.CDLL('libm.so.6')
else:
    print("Windows not supported")

def rounding(x):
    if not isinstance(x, np.ndarray): # scalar
        w, f = str(x).split(".")
        if not w.startswith('-'): # +ve number
            if f.startswith('5'): # midpoint
                libc.fesetround(ROUND_UPWARD)
            else: 
                libc.fesetround(ROUND_TONEAREST)
        if w.startswith('-'):
            if f.startswith('5'):
                libc.fesetround(ROUND_DOWNWARD)
            else:
                libc.fesetround(ROUND_TONEAREST)
        res = np.round(x)
    else: 
        orig_shape = x.shape
        if x.ndim > 1:
            x = x.flatten()
        res = []
        for elem in x:
            w, f = str(elem).split(".")
            if not w.startswith('-'): # -ve number
                if f.startswith('5'): # # midpoint
                    libc.fesetround(ROUND_UPWARD)
                else: 
                    libc.fesetround(ROUND_TONEAREST)
            if w.startswith('-'):
                if f.startswith('5'):
                    libc.fesetround(ROUND_DOWNWARD)
                else:
                    libc.fesetround(ROUND_TONEAREST)
            res.append(np.round(elem))
        res = np.array(res).reshape(orig_shape)
    return res