[BUGFIX] Fix floor divide

[Kacper-Pietkun]

Description

Incorrect rounding of a number.

import numpy as onp
import mxnet as mx


onp_d1 = onp.array([0.941], dtype=onp.float16)
onp_d2 = onp.array([0.1569], dtype=onp.float16)
mx_d1 = mx.numpy.array(onp_d1, dtype=onp.float16)
mx_d2 = mx.numpy.array(onp_d2, dtype=onp.float16)

# 0.941 / 0.1569 = 5.997450605481198
onp_out = onp.floor_divide(onp_d1, onp_d2)  # onp_out = [5.] <= GOOD
mx_out = mx.np.floor_divide(mx_d1, mx_d2)  # mx_out = [6.] <= WRONG

Cause

Incorrect rounding was caused by unnecessary implicit conversion from float to float16 after division but before rounding (5.99745 was saved as 6 during conversion from float to float16, because of lack of precision).

Solution

From now, before doing calculations float16 arguments are explicitly casted to float and they are converted back to float16 only after division and rounding has been made.

Checklist

Essentials

• PR's title starts with a category (e.g. [BUGFIX], [MODEL], [TUTORIAL], [FEATURE], [DOC], etc)
• Changes are complete (i.e. I finished coding on this PR)
• All changes have test coverage

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