Details
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Type:
Sub-task
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Status: Closed
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Priority:
Minor
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Resolution: Fixed
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Affects Version/s: 1.8
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Fix Version/s: None
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Component/s: Questions
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Labels:None
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Affected Branches:MOODLE_18_STABLE
Description
When the answer is a small number i.e 1e-19 as the charge of the electron the range of the allowed answer can extend to negative value given the fact that the code of add +- a small number
line 355 of numerical/questiontype.php in the function get_tolerance_interval(&$answer) {
// We need to add a tiny fraction depending on the set precision to make the
// comparison work correctly. Otherwise seemingly equal values can yield
// false. (fixes bug #3225)
$tolerance = (float)$answer->tolerance + ("1.0e-".ini_get('precision'));
This is to remediate for the 0.000000001 or .999999999 possible output of real number functions.
So if the user put an answer like 1.6e-5 php code could sometimes see it 0.0000159999999 or 0.00001600000001
for small answer values the tiny fraction should be calcualted as a fraction of the number and not an absolute value
actually ("1.0e-".ini_get('precision')); can gives something like 1e-13 for a precision of 8 .
After completing tests, a working solution will be proposed soon
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Issue Links
- is duplicated by
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MDL-12375 Improving the grading of calculated question when there numbers are near the testing limit
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- Closed
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the testing results can be seen in the quiz forum
Small numerical answers i.e. 1e-18 are not graded correctly: testing a solution
http://moodle.org/mod/forum/discuss.php?d=64596
Other tests using the initial tiny fraction in the new code gave coherent values
see
http://moodle.org/mod/forum/discuss.php?d=64596#291061
so the "final" proposition is the following
case '1': case 'relative':
/// Recalculate the tolerance and fall through
/// to the nominal case:
$tolerance = $answer->answer * $tolerance;
// Do not fall through to the nominal case because the tiny fraction is a factor of the answer
$tolerance = abs($tolerance); // important - otherwise min and max are swapped
$max = $answer->answer + $tolerance;
$min = $answer->answer - $tolerance;
break;
case '2': case 'nominal':
$tolerance = abs($tolerance); // important - otherwise min and max are swapped
// $answer->tolerance 0 or something else
if ((float)$answer->tolerance == 0.0 && abs((float)$answer->answer) <= $tolerance )
else if ((float)$answer->tolerance != 0.0 && abs((float)$answer->tolerance) < abs((float)$answer->answer) && abs((float)$answer->answer) <= $tolerance)
{ $tolerance = (1+("1.0e-".ini_get('precision')) )* abs((float) $answer->tolerance) ;//tiny factor }
$max = $answer->answer + $tolerance;
$min = $answer->answer - $tolerance;
break;
This has been proted to the Moodle UQAM (1_6_3 version)
http://moodle.uqam.ca and works correctly.
The files are available on
https://sourceforge.net/projects/moodleuqamchi
fix it using code already tested in Moodle UQAM, do CVS to 18_STABLE and merged TO HEAD.
will merge to 16_stable and 17_stable and then close it
Modifying the line 360 and followings of numerical/questiontype.php to
{ $tolerance = 0.01* abs((float)$answer->answer) ; //arbitrary factor 1.01 }switch ($answer->tolerancetype) {
case '1': case 'relative':
/// Recalculate the tolerance and fall through
/// to the nominal case:
$tolerance = $answer->answer * $tolerance;
// Do not fall through to the nominal case because the tiny fraction is a factor of the answer
$tolerance = abs($tolerance); // important - otherwise min and max are swapped
$max = $answer->answer + $tolerance;
$min = $answer->answer - $tolerance;
break;
case '2': case 'nominal':
$tolerance = abs($tolerance); // important - otherwise min and max are swapped
// $answer->tolerance 0 or something else
if ((float)$answer->tolerance == 0.0 && abs((float)$answer->answer) <= $tolerance )
else if ((float)$answer->tolerance != 0.0 && abs((float)$answer->tolerance) < abs((float)$answer->answer) && abs((float)$answer->answer) <= $tolerance)
{ $tolerance = 1.01 * abs((float) $answer->tolerance) ;//arbitrary factor 1.01 }$max = $answer->answer + $tolerance;
$min = $answer->answer - $tolerance;
break;
solve the problem
More complete report on testing done will follow on moodle docs and or quiz forum.