Duration summary calculates incorrectly

[Anna]

When I link a predecessor task to a task under a subtask, the subtask
duration calculation shows an incorrect calculation. For example, prior to
linking, the subtask shows 2 hours but as soon as I link to a task in another
grouping - the subtask total updates to show 10 hours. It always updates to
show a very high duration. This started last night when I changed my
schedule to be a 24 hour schedule and am wondering if that somehow created a
constraint with a resource?

 

[John]

When I link a predecessor task to a task under a subtask, the subtask
duration calculation shows an incorrect calculation. For example, prior to
linking, the subtask shows 2 hours but as soon as I link to a task in another
grouping - the subtask total updates to show 10 hours. It always updates to
show a very high duration. This started last night when I changed my
schedule to be a 24 hour schedule and am wondering if that somehow created a
constraint with a resource?

Anna,
First of all are any of the linked tasks summary lines? If so, you
definitely will get strange results. Linking summary lines is NOT
recommended. (See FAQ 48 - Summary Task Linking on our MVP website at:
http://www.mvps.org/project/faqs.htm).

Yes, changing to a 24 hour calendar probably will change what you see in
the Duration field. The value in the Duration field is calculated based
on the Hours per day setting under Tools/Options/Calendar tab. If you
are using a 24 hour calendar, that Hours per day setting should be 24
hours.

Please note that changing the Project calendar after a plan is already
in progress can have other strange results, so it is best to set up the
desired calendar before the plan is developed.

Hope this helps.
John
Project MVP

 

[Andre Bal]

John,

I seem to have a similar problem. When a task is not linked to a predecessor
(using 24 hour calender, it's duration is 10 minutes. When i link it to a
predecessor (not summarry task), in the task information it still gives 10
minutes duration, however in the Gant chart is takes one hour. The one hour
is used for the successor of this task to be started.

I work on a comprehensive weekend plan (diaster recovery test) and about 10%
of my 5-15 minute duration task have this problem. Bottom line i have no
reliable leadtime calculation of the plan, not knowing if it can be achieved
in a weekend.

I only use fixed duration task, no resources, and nothing is work driven.
Calender is 24 hour working hours.

When I remove the depedency to the predecessor, than the bar in the gant
chart reduces from 1 hour to 10 minutes.

Bottom line: How is it possible that the leadtime of a task is influenced by
the fact that it has or has NO predecessor, not using resources, and unsing
24 hour working times ? IS this a bug ?

PS: Imported the planning (made in Project 2002) info MSP 2007, and
surprizingly the entire leadtime reduced with one hour, however the problem
still remains

 

[John]

John,

I seem to have a similar problem. When a task is not linked to a predecessor
(using 24 hour calender, it's duration is 10 minutes. When i link it to a
predecessor (not summarry task), in the task information it still gives 10
minutes duration, however in the Gant chart is takes one hour. The one hour
is used for the successor of this task to be started.

I work on a comprehensive weekend plan (diaster recovery test) and about 10%
of my 5-15 minute duration task have this problem. Bottom line i have no
reliable leadtime calculation of the plan, not knowing if it can be achieved
in a weekend.

I only use fixed duration task, no resources, and nothing is work driven.
Calender is 24 hour working hours.

When I remove the depedency to the predecessor, than the bar in the gant
chart reduces from 1 hour to 10 minutes.

Bottom line: How is it possible that the leadtime of a task is influenced by
the fact that it has or has NO predecessor, not using resources, and unsing
24 hour working times ? IS this a bug ?

PS: Imported the planning (made in Project 2002) info MSP 2007, and
surprizingly the entire leadtime reduced with one hour, however the problem
still remains

Andre,
I'd have to take a little time to digest exactly what you are saying and
I have some other things to do right now. Meanwhile, here are a few
things to check.

You say you are using a 24 hour calendar, but what is the setting under
Tools/Options/Calendar, the "Hours per day" value? It should be 24 also.
You should also have the default start and end times set to 12:00 am and
11:59 pm respectively

Do you have calculation set for automatic (Tools/Options/Calculation
tab)?

How did you enter the tasks? Did you type a start time directly into the
Start field? If so, that automatically sets a constraint of
"start-no-earlier-than".

John
Project MVP

 

[Steve House]

Remember the duration of a summary task is NOT the arithmetic sum of the
durations of its subtasks. Instead a summary task duration extends from the
start of its earliest starting subtask until the end of the latest finishing
subtask. As an example, I have a summary task consisting of two, 1-hour
duration subtasks. Default calendar. The subtasks are linked FS. Subtask
1 starts Monday 8am. Subtask 2 has a Start No Earlier Than constraint of
Wednesday at noon, thus placing its scheduled start at 1pm and finish at
2pm. The duration of the summary task is 2 days and 5 hours, from 8am
Monday until 2pm Wednesday, and NOT 2 hours, the sum of the subtask
durations.