Re: [tablix-list] Pale grey means, "I've scheduled a lesson you didn't ask for"!?

From: Nicholas Robinson <>
Date: Tue Dec 21 2004 - 19:34:55 CET


Your explanation certainly sound plausible. It may be the cause of some or all
of the problems I am having. I usually get down to around 24 timeplace errors
which are caused, if you are right, because it can't schedule the lessons
into what it thinks is an already full timetable - actually over-full because
I use one 'core' class to schedule games and CDT for two years and another
for each year to schedule English, Maths and sometimes French to an
individual year, with lowest level hierarchy being the sets.This results in
conflicts with up to 6 other classes, the result is that the top hierarchy
has 3X tuples, the middle hierarchy 2X and lowest level X where X is the
number of lessons per week.

What is strange is that it doesn't always have enough tuples - sometimes there
are 1,2 or even 3 missing from the sets and these depress the higher level
class counts. Eventually, if the run goes on long enough the sets all show 41
tuples which is the correct answer. I haven't read anywhere that it delays
adding tuples, I thought it set them all up at the outset.

Because of the problems I've had with forcesametime, I've used this
heirarachical approach with more-rooms and more-teachers to create enough
sets. I think I might try to use the 'group' way though as it would make it
easier to produce output that doesn't need editing or further processing.



On Tuesday 21 December 2004 15:33, John Winters wrote:
> I've made some further progress investigating the pale grey lessons.
> Counting up the lessons in my timetable there should be 5 groups, each
> having 3 double maths lessons and 5 groups, each having 3 double english
> lessons, making 60 individual lessons in all.
> The html timetable as produced shows 72 lessons, but the output file
> (result0.xml) lists only 60. However, the first thing I then note is
> that there are 12 greyed-out lessons, which exactly makes up the
> difference. Further, the greyed-out lessons always appear at the same
> time as a real lesson is taking place for the "conflicts-with" group.
> It's as if the timetabler is trying to say, "The reason there isn't a
> lesson happening here is because it conflicts with this lesson".
> That in itself wouldn't be a problem (once we've discovered what the
> greyed-out lesson means) but the effect seems to go further. It appears
> that some sort of equivalence between groups is set up, to the extent
> that the "forcesametime" module regards a state of "Unable to have a
> lesson due to explicit conflict" as being the same as "Having a
> lesson". Thus, looking at Monday in the attached file we find that
> 9-MAT3 has its Maths lesson at a different time from 9-MAT1, despite the
> explicit requirement that they should be at the same time. However,
> 9-MAT3's Maths lesson is at the same time as 9-MAT1 is *prevented* from
> having a Maths lesson by the shadow of 9-ENG1's English lesson.
> This same pattern follows through in all the errors in the results so
> I'm pretty confident it's a correct explanation.
> Now to dig into the code to see exactly why it's happening.
> John
Received on Tue Dec 21 19:45:53 2004

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