Deadline works opposite to how it should

[Joaquim Amado Lopes]

Greetings.

I have 2 tasks (T1 and T2), same duration, no constraints (as soon as
possible) nor predecessors. Both tasks use the same resource (R1).
Only one unit of the resource is available.
Leveling automatic and leveling order "standart" or "priority,
standard" (same result).

Naturally, one of the tasks (the one with the higher ID) slips, as
there is only one resource available.
But, if I set a deadline to the task that is schedulled for earlier,
this task slips and is the other one that is done earlier, even if it
causes a conflit with the deadline.

This happens both in:
Project Standard 2002 (10.0.2104.1305) SP-1
Project Professional 2003 (11.0.2003.0816.15)

Tried it with more tasks and those with a deadline slip to as late as
possible. Seems like Project is actually trying to miss the deadlines.

Shouldn't it be the other way around?

Thank you for help,
Joaquim Amado Lopes

 

[Jan De Messemaeker]

I've never seen this, but I'll look into it.
I have an idea how this could come aboiut but have to test it.
I'll be back.

 

[JulieS]

Hi Joaquim & Jan,

Pardon me for jumping in. I *believe* the reason that Project chooses to
delay the task with the deadline is due to the total slack and Late Finish of
the tasks. When you set a deadline on a task that is later than the
scheduled finish date, Project uses the deadline date as the Late Finish for
the task and calculates total slack accordingly. The "Standard" leveling
order and the "Priority, Standard" uses total slack as one of the criteria
for deciding which task gets delayed and also appears to use the Late Finish
date. (Project does make mention of "Scheduling Date" in help when viewing
information about which factors are used to determine which task is delayed.)

For example, if I create two tasks (T1, T2) both starting today. T1 is 5
days in duration with a Finish Date of 25, May 2005. T2 is 2 days duration
with a Finish Date of 20, May 2005.
T1 has 0 total slack - Late Finish 25, May 2005 T2 has 3 days total slack -
Late Finish 25, May 2005. If I add a deadline to T1 of 26, May 2005, T1 now
has 1 day total slack but has a Late Finish Date of 26, May 2005. Even
though T1 has less Total slack, the Late Finish date is later than the Late
Finish of T2. Project chooses to delay the task with the later finish date,
even if it misses the deadline.

Hope this helps.

Julie

 

[Joaquim Amado Lopes]

Greetings.

Pardon me for jumping in.

I appreciate all help I can get. :-]

I *believe* the reason that Project chooses to
delay the task with the deadline is due to the total slack and Late Finish of
the tasks. When you set a deadline on a task that is later than the
scheduled finish date, Project uses the deadline date as the Late Finish for
the task and calculates total slack accordingly.

I tested this and it is true. When you set a deadline, Project uses
that as the Late Finish date.

[snip]

Project chooses to delay the task with the later finish date,
even if it misses the deadline.

The problem is that it doesn't happen like that. Several tests I did,
Project always delays the task with the deadline, regardless the
dealine/Late Finish dates are sooner that the Late Finish of the other
tasks.
In other words, if, in a group of simmilar tasks that require the same
resource, you don't set any deadline, Project delays the task with
the higher ID. If you set a deadline to one of the tasks, that is the
one delayed, regardless if it misses the dealine.

Project always chooses the worst possible solution, considering the
deadlines.

Hope this helps.

It didn't solve my problem but I learned one more detail of Project.
Thanks. :-]

Take care,
Joaquim Amado Lopes

 

[Steve House [Project MVP]]

This is certainly a puzzle and may turn out to be a true logic bug in the
leveling algorithm. I had not noticed it before but after reading your post
I set up a little trial plan and you're absolutely right. As far as slack
time calculations are concerned, Project treats tasks with a deadline and
tasks with a MFNLT exactly the same way and the leveling behavior you expect
makes perfect sense. In fact, a task with a deadline should behave exactly
the same as a task with a MFNLT constraint with the "tasks always obey
constraint dates" global setting turned off - slack time is calculated based
on the "constraint" but there are no restrictions on where the task is
placed in the schedule.

There's another interesting wrinkle to this I just discovered: Create 2
5-day tasks A & B in a project starting next Monday the 23rd. Put a
deadline of 30 May on task A. Assign Joe Resource to both tasks 100%.
Level with the "only within available slack" setting turned on. Project
balks and says it can't resolve the conflict but when you hit "skip all" in
the message box, the resulting schedule moves BOTH tasks to start the 24th,
slipping A until it hits the deadline and moving B in lock-step with it!
Very weird. Not only does it not resolve the overallocation, it makes sure
it doesn't even come up with a partial solution resolving the one day it
actually could have done!

 

[Joaquim Amado Lopes]

Greetings.

This is certainly a puzzle and may turn out to be a true logic bug in the
leveling algorithm. I had not noticed it before but after reading your post
I set up a little trial plan and you're absolutely right. As far as slack
time calculations are concerned, Project treats tasks with a deadline and
tasks with a MFNLT exactly the same way and the leveling behavior you expect
makes perfect sense.

[snip]
This is a real problem for me as the prototype I'm developing for a
production unit requires each job order (as a summary tasks with a
number of sub-tasks) to have a deadline. If Project goes out of it's
way to make sure the deadlines aren't met, the prototype is useless.

Also, I discovered that, after messing a bit with the information of
the tasks (duration, predecessors, constraints, ...) to find out how
Project works on different situations (as it doesn't seem to be
working as it should), it stops leveling at all and doesn't even
process the links.
Also, the durations of the summary tasks were 'locked' until I changed
the duration of sub-tasks a couple of times and it recalculated
everything.

Has anyone experienced these problems or can it be something wrong
with my installation of Project? Note that I have Project 2002 and
2003 installed (in different folders).

Thank you,
Joaquim Amado Lopes

 

[Steve House [Project MVP]]

Not sure what you mean when you say the duration of a summary is "locked."
Summary task durations are always calculated values, determined by the time
from the earliest starting subtask to the latest ending subtask - as such
they are read only and cannot be manually updated, nor will they always
change in response to a subtask's duration change since they're not a simple
arithmetic sum. If you have a summary that consists of 5 unlinked subtasks,
starting at the same time and running for 1, 2, 3, 4, and 5 days
respectively, the duration of the summary will be 5 days. If you edit the
duration of Subtask 1, changing it from 1 to 4 days, for example, the
summary task duration will remain at 5 days. Only if one of those tasks
changed to be 6 days or more, or task was 5 reduced to less than 5 days
would the summary duration change. Links, leveling, constraints, or
anything that causes the subtasks to run other than in parallel may change
the specific numbers but the principle of the behavior will remain - the
duration of a summary task is number of working time calendar time units
between the point when work is first done on any one of its component
subtasks until the last bit of work is performed on any one of the subtasks.
If this is what you meant by "locked" and refusing to change unless you
fiddle with the subtasks a while, then that is exactly how it is supposed to
work and it simply took you several experiments before you happen to hit on
a subtask change that affected the earliest start or latest finish of the
set taken as a group.
--
Steve House [MVP]
MS Project Trainer & Consultant
Visit http://www.mvps.org/project/faqs.htm for the FAQs

Greetings.

This is certainly a puzzle and may turn out to be a true logic bug in the
leveling algorithm. I had not noticed it before but after reading your
post
I set up a little trial plan and you're absolutely right. As far as slack
time calculations are concerned, Project treats tasks with a deadline and
tasks with a MFNLT exactly the same way and the leveling behavior you
expect
makes perfect sense.

[snip]
This is a real problem for me as the prototype I'm developing for a
production unit requires each job order (as a summary tasks with a
number of sub-tasks) to have a deadline. If Project goes out of it's
way to make sure the deadlines aren't met, the prototype is useless.

Also, I discovered that, after messing a bit with the information of
the tasks (duration, predecessors, constraints, ...) to find out how
Project works on different situations (as it doesn't seem to be
working as it should), it stops leveling at all and doesn't even
process the links.
Also, the durations of the summary tasks were 'locked' until I changed
the duration of sub-tasks a couple of times and it recalculated
everything.

Has anyone experienced these problems or can it be something wrong
with my installation of Project? Note that I have Project 2002 and
2003 installed (in different folders).

Thank you,
Joaquim Amado Lopes

 

[Joaquim Amado Lopes]

Greetings.

Not sure what you mean when you say the duration of a summary is "locked."

[snip]
A summary task with 2 sub-tasks (one day each) linked with FS. The
duration of the summary task is 2 days.
After the 'experiments' I mentioned before, the two sub-tasks are
schedulled for the same day (don't ask me how it happened) and the
link and resource limitations are being ignored. As the two sub-tasks
are schedulled for the same day, the calculated duration of the
summary task should be 1 day but it isn't. It is 'locked' in 2 days.

I removed the link and add it again. Nothing changed.
Removed the resources, add them again to the tasks, leveled them and
again nothing changed in the summary task.
Add more tasks and linked them to the others. They remained all
schedulled for the same day.

Only when I changed the duration of one of the sub-tasks to 5 or 6
days and back to 1 day the summary task duration was recalculated.
Also, the Latest Finish dates weren't changing as they should.

I tell you, it was the weirdest thing I ever saw.

I don't remember these kind of things happening with previous versions
of Project but I never experimented so much with deadlines nor had 2
different versions of Project installled on my computer at the same
time before.

What I'm trying to find out is if the problem is with my computer or
with Project.

Cheers,
Joaquim Amado Lopes

 

[Steve House [Project MVP]]

Take a look at the usage views and see if one of those tasks shows 1 day
with zero hours for the first day. If task A shows 1 day duration but the
usage shows a day of zero hours and a day of 8 hours, then the summary task
will see this as being a 2 day task with a duration of 1 day and so the
summary duration will be 2 days!!!! Go figure!

Very weird.
--
Steve House [MVP]
MS Project Trainer & Consultant
Visit http://www.mvps.org/project/faqs.htm for the FAQs

Greetings.

Not sure what you mean when you say the duration of a summary is "locked."

[snip]
A summary task with 2 sub-tasks (one day each) linked with FS. The
duration of the summary task is 2 days.
After the 'experiments' I mentioned before, the two sub-tasks are
schedulled for the same day (don't ask me how it happened) and the
link and resource limitations are being ignored. As the two sub-tasks
are schedulled for the same day, the calculated duration of the
summary task should be 1 day but it isn't. It is 'locked' in 2 days.

I removed the link and add it again. Nothing changed.
Removed the resources, add them again to the tasks, leveled them and
again nothing changed in the summary task.
Add more tasks and linked them to the others. They remained all
schedulled for the same day.

Only when I changed the duration of one of the sub-tasks to 5 or 6
days and back to 1 day the summary task duration was recalculated.
Also, the Latest Finish dates weren't changing as they should.

I tell you, it was the weirdest thing I ever saw.

I don't remember these kind of things happening with previous versions
of Project but I never experimented so much with deadlines nor had 2
different versions of Project installled on my computer at the same
time before.

What I'm trying to find out is if the problem is with my computer or
with Project.

Cheers,
Joaquim Amado Lopes