[samigo-team] Floating point numbers

[Sam Ottenhoff]

Okay, I attached a patch to https://jira.sakaiproject.org/browse/SAM-2087.

I also have a demo server up: http://198.30.168.81:15150/portal/.  Sakai
demo mode is enabled so you can login with a username like
instructor1/sakai or student0012/sakai.

All of my tests look good so far.  This change makes sense to me.  The
gradebook uses double-precision numbers for recording points.  Samigo
should do the same thing.

This is a large change.  It essentially changes all occurrences of floats
with doubles.

--Sam


On Tue, Mar 5, 2013 at 11:34 AM, Sam Ottenhoff <ottenhoff at longsight.com>wrote:

> I gave it a try, but it involves 1000+ changes.  It probably makes sense
> to just improve precision and move from floats to doubles instead.  The
> gradebook records POINTS_EARNED as a double.
>
>
> On Thu, Feb 28, 2013 at 2:16 PM, Karen Tsao <ktsao at stanford.edu> wrote:
>
>> Thanks for everyone's input.
>>
>> Sam,
>>
>> Could you please make the change? Thanks!
>>
>> Karen
>>
>>
>> On Thu, Feb 28, 2013 at 6:19 AM, David Horwitz <david.horwitz at uct.ac.za>wrote:
>>
>>>  There's a another issue (fixable without replacing floats but still)
>>>
>>> There are several places in the code where direct foat comparisons are
>>> made:
>>>
>>> Float a =
>>> Float b,
>>>
>>> if (a.equals(b))
>>>
>>> For instance to check if an answer has been updated etc. We could be
>>> getting extra updated because of slight differences in the float
>>> representation ...
>>>
>>> D
>>>
>>>
>>> On Thu, 2013-02-28 at 09:11 -0500, Sam Ottenhoff wrote:
>>>
>>>
>>>  But just curious, what is the advantage of this change? Is this for
>>> getting a more precise score? Like some 0.999 issue?
>>>
>>>
>>>
>>>  An instructor created a complex placement exam that used point scores
>>> in the millions, thousands, hundreds, etc. as a way of being able to
>>> quickly see points in various sections in the final score (example:
>>> 27005508.06 could be broken up to see that the student scores 06 on sec 1,
>>> 08, on sec 2, 55 on sec 3, 27 on sec 4).
>>>
>>>
>>>
>>>  So the reason why floating point numbers aren't used for money:
>>>
>>>
>>>
>>>  > create table floattest (z float);
>>>
>>> > insert into floattest VALUES (*2075808*);
>>>
>>> > select * from floattest;
>>>
>>>
>>>
>>>  The result: *2075810*
>>>
>>>  _______________________________________________
>>> samigo-team mailing listsamigo-team at collab.sakaiproject.orghttp://collab.sakaiproject.org/mailman/listinfo/samigo-team
>>>
>>>
>>> ------------------------------
>>> UNIVERSITY OF CAPE TOWN
>>>
>>> This e-mail is subject to the UCT ICT policies and e-mail disclaimer
>>> published on our website at
>>> http://www.uct.ac.za/about/policies/emaildisclaimer/ or obtainable from +27
>>> 21 650 9111. This e-mail is intended only for the person(s) to whom it
>>> is addressed. If the e-mail has reached you in error, please notify the
>>> author. If you are not the intended recipient of the e-mail you may not
>>> use, disclose, copy, redirect or print the content. If this e-mail is not
>>> related to the business of UCT it is sent by the sender in the sender's
>>> individual capacity.
>>>
>>
>>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://collab.sakaiproject.org/pipermail/samigo-team/attachments/20130310/585fd5a4/attachment.html