diff --git a/common/lib/capa/capa/responsetypes.py b/common/lib/capa/capa/responsetypes.py
index cd2b81fc1cb422db97442ff2bad78f467fc9b7f1..86f99f26747ba41b90ba81741cc696f2f2833305 100644
--- a/common/lib/capa/capa/responsetypes.py
+++ b/common/lib/capa/capa/responsetypes.py
@@ -48,6 +48,7 @@ import capa.safe_exec as safe_exec
import capa.xqueue_interface as xqueue_interface
from openedx.core.djangolib.markup import HTML, Text
from openedx.core.lib import edx_six
+from openedx.core.lib.grade_utils import round_away_from_zero
from . import correctmap
from .registry import TagRegistry
@@ -727,7 +728,7 @@ class ChoiceResponse(LoncapaResponse):
good_non_answers = sum([1 for blank in student_non_answers if blank in self.incorrect_choices])
edc_current_grade = good_answers + good_non_answers
- return_grade = round(self.get_max_score() * float(edc_current_grade) / float(edc_max_grade), 2)
+ return_grade = round_away_from_zero(self.get_max_score() * float(edc_current_grade) / float(edc_max_grade), 2)
if edc_current_grade == edc_max_grade:
return CorrectMap(self.answer_id, correctness='correct')
@@ -764,10 +765,10 @@ class ChoiceResponse(LoncapaResponse):
return_grade = self.get_max_score()
return CorrectMap(self.answer_id, correctness='correct', npoints=return_grade)
elif halves_error_count == 1 and len(all_choices) > 2:
- return_grade = round(self.get_max_score() / 2.0, 2)
+ return_grade = round_away_from_zero(self.get_max_score() / 2.0, 2)
return CorrectMap(self.answer_id, correctness='partially-correct', npoints=return_grade)
elif halves_error_count == 2 and len(all_choices) > 4:
- return_grade = round(self.get_max_score() / 4.0, 2)
+ return_grade = round_away_from_zero(self.get_max_score() / 4.0, 2)
return CorrectMap(self.answer_id, correctness='partially-correct', npoints=return_grade)
else:
return CorrectMap(self.answer_id, 'incorrect')
diff --git a/common/lib/xmodule/xmodule/lti_2_util.py b/common/lib/xmodule/xmodule/lti_2_util.py
index 0e15fd1f8be94e710e7bfed125ce63293d96c924..d32f7a41f951d830e667abdf758f2fa5a968a6b9 100644
--- a/common/lib/xmodule/xmodule/lti_2_util.py
+++ b/common/lib/xmodule/xmodule/lti_2_util.py
@@ -18,6 +18,7 @@ from oauthlib.oauth1 import Client
from six import text_type
from webob import Response
from xblock.core import XBlock
+from openedx.core.lib.grade_utils import round_away_from_zero
log = logging.getLogger(__name__)
@@ -177,7 +178,7 @@ class LTI20ModuleMixin(object):
return Response(json.dumps(base_json_obj).encode('utf-8'), content_type=LTI_2_0_JSON_CONTENT_TYPE)
# Fall through to returning grade and comment
- base_json_obj['resultScore'] = round(self.module_score, 2)
+ base_json_obj['resultScore'] = round_away_from_zero(self.module_score, 2)
base_json_obj['comment'] = self.score_comment
return Response(json.dumps(base_json_obj).encode('utf-8'), content_type=LTI_2_0_JSON_CONTENT_TYPE)
diff --git a/lms/djangoapps/class_dashboard/dashboard_data.py b/lms/djangoapps/class_dashboard/dashboard_data.py
index a53007b2cc79d4292c9910b5564499d0b2c3b0ba..038625b2662656f9c3faf2bb2413c0beec041713 100644
--- a/lms/djangoapps/class_dashboard/dashboard_data.py
+++ b/lms/djangoapps/class_dashboard/dashboard_data.py
@@ -16,6 +16,7 @@ from lms.djangoapps.instructor_analytics.csvs import create_csv_response
from util.json_request import JsonResponse
from xmodule.modulestore.django import modulestore
from xmodule.modulestore.inheritance import own_metadata
+from openedx.core.lib.grade_utils import round_away_from_zero
# Used to limit the length of list displayed to the screen.
MAX_SCREEN_LIST_LENGTH = 250
@@ -193,7 +194,7 @@ def get_d3_problem_grade_distrib(course_id):
for (grade, count_grade) in problem_info['grade_distrib']:
percent = 0.0
if max_grade > 0:
- percent = round((grade * 100.0) / max_grade, 1)
+ percent = round_away_from_zero((grade * 100.0) / max_grade, 1)
# Compute percent of students with this grade
student_count_percent = 0
@@ -352,7 +353,7 @@ def get_d3_section_grade_distrib(course_id, section):
for (grade, count_grade) in grade_distrib[problem]['grade_distrib']:
percent = 0.0
if max_grade > 0:
- percent = round((grade * 100.0) / max_grade, 1)
+ percent = round_away_from_zero((grade * 100.0) / max_grade, 1)
# Construct tooltip for problem in grade distibution view
tooltip = {
@@ -513,7 +514,7 @@ def get_students_problem_grades(request, csv=False):
student_dict['percent'] = 0
if student['max_grade'] > 0:
- student_dict['percent'] = round(student['grade'] * 100 / student['max_grade'])
+ student_dict['percent'] = round_away_from_zero(student['grade'] * 100 / student['max_grade'])
results.append(student_dict)
max_exceeded = False
@@ -535,7 +536,7 @@ def get_students_problem_grades(request, csv=False):
for student in students:
percent = 0
if student['max_grade'] > 0:
- percent = round(decimal.Decimal(student['grade'] * 100 / student['max_grade']), 1)
+ percent = round_away_from_zero((student['grade'] * 100 / student['max_grade']), 1)
results.append([student['student__profile__name'], student['student__username'], student['grade'], percent])
response = create_csv_response(filename, header, results)
diff --git a/lms/djangoapps/grades/course_grade.py b/lms/djangoapps/grades/course_grade.py
index dcc5bf363b7b8d899a2c067c105c7b00025c9a3e..fb8181d7daf0d381b97e1d9d8d4a0849c48626d2 100644
--- a/lms/djangoapps/grades/course_grade.py
+++ b/lms/djangoapps/grades/course_grade.py
@@ -12,6 +12,7 @@ from django.conf import settings
from django.utils.encoding import python_2_unicode_compatible
from lazy import lazy
+from openedx.core.lib.grade_utils import round_away_from_zero
from xmodule import block_metadata_utils
from .config import assume_zero_if_absent
@@ -296,7 +297,9 @@ class CourseGrade(CourseGradeBase):
Computes and returns the grade percentage from the given
result from the grader.
"""
- return round(grader_result['percent'] * 100 + 0.05) / 100
+
+ # Confused about the addition of .05 here? See https://openedx.atlassian.net/browse/TNL-6972
+ return round_away_from_zero(grader_result['percent'] * 100 + 0.05) / 100
@staticmethod
def _compute_letter_grade(grade_cutoffs, percent):
diff --git a/lms/djangoapps/instructor/tests/test_spoc_gradebook.py b/lms/djangoapps/instructor/tests/test_spoc_gradebook.py
index 078d753c6664066c9bed7b68463633a619947c36..1fa34bbf04cae1538b3270f956958ee7eb641eac 100644
--- a/lms/djangoapps/instructor/tests/test_spoc_gradebook.py
+++ b/lms/djangoapps/instructor/tests/test_spoc_gradebook.py
@@ -104,11 +104,11 @@ class TestDefaultGradingPolicy(TestGradebook):
# Users 1-10 attempted any homework (and get Fs) [10]
# Users 4-10 scored enough to not get rounded to 0 for the class (and get Fs) [7]
# One use at top of the page [1]
- self.assertEqual(22, self.response.content.count(b'grade_F'))
+ self.assertEqual(23, self.response.content.count(b'grade_F'))
# All other grades are None [29 categories * 11 users - 27 non-empty grades = 292]
# One use at the top of the page [1]
- self.assertEqual(293, self.response.content.count(b'grade_None'))
+ self.assertEqual(292, self.response.content.count(b'grade_None'))
class TestLetterCutoffPolicy(TestGradebook):
diff --git a/openedx/core/lib/grade_utils.py b/openedx/core/lib/grade_utils.py
index 601b994d133709863e6cc3e2eadd796599a5a464..2e7073e962dcf1406382f85d77cd1aa553abb7a8 100644
--- a/openedx/core/lib/grade_utils.py
+++ b/openedx/core/lib/grade_utils.py
@@ -1,6 +1,7 @@
"""
Helpers functions for grades and scores.
"""
+import math
def compare_scores(earned1, possible1, earned2, possible2, treat_undefined_as_zero=False):
@@ -42,3 +43,26 @@ def is_score_higher_or_equal(earned1, possible1, earned2, possible2, treat_undef
"""
is_higher_or_equal, _, _ = compare_scores(earned1, possible1, earned2, possible2, treat_undefined_as_zero)
return is_higher_or_equal
+
+
+def round_away_from_zero(number, digits=0):
+ """
+ Round numbers using the 'away from zero' strategy as opposed to the
+ 'Banker's rounding strategy.' The strategy refers to how we round when
+ a number is half way between two numbers. eg. 0.5, 1.5, etc. In python 2
+ positive numbers in this category would be rounded up and negative numbers
+ would be rounded down. ie. away from zero. In python 3 numbers round
+ towards even. So 0.5 would round to 0 but 1.5 would round to 2.
+
+ See here for more on floating point rounding strategies:
+ https://en.wikipedia.org/wiki/IEEE_754#Rounding_rules
+
+ We want to continue to round away from zero so that student grades remain
+ consistent and don't suddenly change.
+ """
+ p = 10.0 ** digits
+
+ if number >= 0:
+ return float(math.floor((number * p) + 0.5)) / p
+ else:
+ return float(math.ceil((number * p) - 0.5)) / p
diff --git a/openedx/core/lib/tests/test_grade_utils.py b/openedx/core/lib/tests/test_grade_utils.py
index 9c4f08216d993e9aa545307ff082778de32081aa..4d6dd00912834f6fe6475e110515c14f9df144e5 100644
--- a/openedx/core/lib/tests/test_grade_utils.py
+++ b/openedx/core/lib/tests/test_grade_utils.py
@@ -7,7 +7,7 @@ from unittest import TestCase
import ddt
-from ..grade_utils import compare_scores
+from ..grade_utils import compare_scores, round_away_from_zero
@ddt.ddt
@@ -45,3 +45,15 @@ class TestGradeUtils(TestCase):
assert is_higher is True
assert 0 == percentage_1
assert 0 == percentage_2
+
+ @ddt.data(
+ (0.5, 1),
+ (1.45, 1.5, 1),
+ (-0.5, -1.0),
+ (-0.1, -0.0),
+ (0.1, 0.0),
+ (0.0, 0.0)
+ )
+ @ddt.unpack
+ def test_round_away_from_zero(self, precise, expected_rounded_number, rounding_precision=0):
+ assert round_away_from_zero(precise, rounding_precision) == expected_rounded_number