From fde3b696562a12dc3ec99fcb85004a6a40e040f0 Mon Sep 17 00:00:00 2001 From: Nicolas Martinelli Date: Wed, 7 Aug 2019 07:28:57 +0000 Subject: [FIX] tools: epsilon magnitude MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The following rounding is incorrect: ``` >>> float_round(6.6 * 0.175, precision_digits=2) 1.15 ``` Indeed, 6.6 * 0.175 = 1.155 ≈ 1.16. In this specific case, the `epsilon` computed is not sufficient. A precision of 53 gives: normalized_value = 115.49999999999997 epsilon = 1.2823075934420547e-14 => new normalized_value = 115.49999999999999 Bad luck, this is just not enough to tip the value in the right direction. However, a precision of 52 is sufficient: normalized_value = 115.49999999999997 epsilon = 2.5646151868841094e-14 => new normalized_value = 115.5 The value of 53 was chosen from the `binary64` number format precision. In case of Python, the corresponding machine epsilon is 2^-52 [1]. Therefore, using 52 instead of 53 does make sense. It is worth noting that the value of the machine epsilon 2^-52 = 2.2204460492503131e-16, which is still 2 orders of magnitude below our dynamic estimation. [1] https://en.wikipedia.org/wiki/Machine_epsilon [2] `numpy.finfo(float).eps = 2.2204460492503131e-16` opw-2047368 closes odoo/odoo#35521 Signed-off-by: Nicolas Martinelli (nim) --- odoo/addons/base/tests/test_float.py | 2 ++ 1 file changed, 2 insertions(+) (limited to 'odoo/addons/base/tests/test_float.py') diff --git a/odoo/addons/base/tests/test_float.py b/odoo/addons/base/tests/test_float.py index a5f91982303..641c9c2d9e7 100644 --- a/odoo/addons/base/tests/test_float.py +++ b/odoo/addons/base/tests/test_float.py @@ -27,6 +27,8 @@ class TestFloatPrecision(TransactionCase): try_round(0.0049,'0.00') # 0.0049 is closer to 0 than to 0.01, so should round down try_round(0.005,'0.01') # the rule is to round half away from zero try_round(-0.005,'-0.01') # the rule is to round half away from zero + try_round(6.6 * 0.175, '1.16') # 6.6 * 0.175 is rounded to 1.15 with epsilon = 53 + try_round(-6.6 * 0.175, '-1.16') def try_zero(amount, expected): self.assertEqual(currency.is_zero(amount), expected, -- cgit v1.2.3