How Does Project calculate

[Deluth]

I would like to know when and how Project does its calculations. My resources sometimes change the order of the tasks they're doing. Sometimes, a later task starts before the earlier task. When this occurs, I enter the percent complete into the later task. When I open up the project again, the end date seemed to have been recalculated based on the percent completed and the remaining duration. Unfortunately, when I try to repeat this to see how Project calculates, it doesn't. As if it only calculates when there's been some time passed since the last time the project was opened.

I know that Project calculates when the acutal finish (or 100% complete) has been entered. But I am seeing that it sometime calculates on percentages as well. I would like to know when does it do this and how does it calculate, as well as, why sometimes and not others...

Thannks in advance for any help...

 

[Jan De Messemaeker]

Hi,

(I hope we are talking stand alone projects not project linked to a lot of
other ones in a pool or in Project Server)
When in tools, option, calculation, Automatic is on calculation happens
instantaneously, immediately, on the spot.
If not it happens when you hit the calculate button.

It recalculates things when they have changed. Putting tasks to 100% doesn't
necessarily change dates (to the contrary).
And when you want to understand calculations, do not enter a percent
complete. IMHO a percentage is the result of a calculation and not an input.

HTH

--
Jan De Messemaeker
Microsoft Project Most Valuable Professional
http://users.online.be/prom-ade/index.htm
32-495-300 620

I would like to know when and how Project does its calculations. My

resources sometimes change the order of the tasks they're doing. Sometimes,
a later task starts before the earlier task. When this occurs, I enter the
percent complete into the later task. When I open up the project again, the
end date seemed to have been recalculated based on the percent completed and
the remaining duration. Unfortunately, when I try to repeat this to see how
Project calculates, it doesn't. As if it only calculates when there's been
some time passed since the last time the project was opened.

I know that Project calculates when the acutal finish (or 100% complete)

has been entered. But I am seeing that it sometime calculates on
percentages as well. I would like to know when does it do this and how does
it calculate, as well as, why sometimes and not others...

 

[Steve House]

Alarm bells are going off here. You say "a later task is being done before
the earlier task." That may be the proximate cause of the splits you are
getting but it should not be happening. Predecessor/successor links mean
there is a real physical reason that the later task cannot, under any
circumstances, start until the predecessor has finished (assuming a
finish-start link for simplicity). Putting on the roof is not a successor
to erecting the walls because that's the order we want to do it in. It is a
successor because the law of gravity doesn't give us the option of building
the roof in midair and stuffing the walls in later <grin>. If it possible
for that later task to start before the earlier one (and it obviously is, or
else your resources would not have been able to do what they're reporting to
you that they did), you should not have the link there in the first place.
I'd strongly suggest you review the dependencies in your project plan to
make sure they are valid, serving the function of making the plan a real
engineering model of the physical process of creating the project's
deliverables and are not in there to force the plan into some pre-conceived
idea of the way the work "should" progress.


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

I would like to know when and how Project does its calculations. My

resources sometimes change the order of the tasks they're doing. Sometimes,
a later task starts before the earlier task. When this occurs, I enter the
percent complete into the later task. When I open up the project again, the
end date seemed to have been recalculated based on the percent completed and
the remaining duration. Unfortunately, when I try to repeat this to see how
Project calculates, it doesn't. As if it only calculates when there's been
some time passed since the last time the project was opened.

I know that Project calculates when the acutal finish (or 100% complete)

has been entered. But I am seeing that it sometime calculates on
percentages as well. I would like to know when does it do this and how does
it calculate, as well as, why sometimes and not others...

 

[Deluth]

Steve,

Perhaps I am using Project incorrectly. I am managing a software team. I set precedences for the tasks in order to try to set the sequential order of tasks to be completed by any given resource - this is how the resource knows what to tackle next. There are linkages in there that are strict, by this I mean that the preceeding tasks absolutely need to complete before the succeeding tasks can occur. However, most of the tasks are linked to determine the sequence of events to occur. The linkage also allows me to figure out when the project would complete. using this method, the resource can easily move around on the tasks since they're weakly linked. If the resource feels that they want to complete the tasks out of order, I just re-order it the way they need to get it done. This is almost as if you would start working on assembling the roof while you wait for more woods to arrive for the completion of the wall, once you complete the wall, you can finish up on the roof and assemble the house...

If you can suggest how I can make sure the resources are utilized correctly without linking sequential tasks, please let me know. I am anxious to learn any new concepts.

Thanks!

 

[Steve House]

There are such things as "discressionary links" which is what you are
describing but IMO they are should be used very sparingly. Take this
example of an alternate approach. I have programmer Jim who needs to work
on several 5 day long tasks A, B, C, and D. Each will require his undivided
attention so he can't work on them concurrently. The preferred sequence for
the first 3 is A-B-C but it is not mandatory that they be done in this
order, they are essentially independent of each other and there's no
mandatory process reason one must be done before the other. All three,
OTOH, must be done before task D - the program rollout perhaps - can be
started. The whole thing kicks off next Monday so that's the Project start
date. My initial project plan would show tasks A, B, and C all starting
next Monday and running concurrently through the week. None of them are
linked to each other, but all three have links FS as predecessors to task D
so D would start the following Monday, giving a total project timeline at
this point in the planning cycle of 2 weeks. Now I assign Jim to all 4
tasks. Because he's assigned 100% of his workday to each of A, B, and C,
he's overallocated to the tune of 300% all next week. Resource levelling
will fix that but first I want to look at the desired sequence the tasks
should be performed if they can't be done all at once and I decide I'd like
A to go first, then B, then C. Of course if they *could* be done together
I'd go that route since the overall planning objective is to finish the
project in the shortest possible time consistent with staying in budget. So
before levelling, I designate A as a high priority task, B somewhat lower,
and C a bit lower still. Now when we level, Project delays work to resolve
the overallocation, pushing out C first, then B. So we end up with a
Project schedule running 4 weeks, in the sequence A-B-C-D *without* any
links between A, B, and C. Now we find another fellow available in the 2nd
week that can do similar work. I substitute him for Jim on task B, C jumps
forward a week with Jim still on it and our schedule immediately revises
showing B & C running concurrently in the 2nd week, and the overall schedule
shortens by one week.


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

Steve,

Perhaps I am using Project incorrectly. I am managing a software team. I

set precedences for the tasks in order to try to set the sequential order of
tasks to be completed by any given resource - this is how the resource knows
what to tackle next. There are linkages in there that are strict, by this I
mean that the preceeding tasks absolutely need to complete before the
succeeding tasks can occur. However, most of the tasks are linked to
determine the sequence of events to occur. The linkage also allows me to
figure out when the project would complete. using this method, the resource
can easily move around on the tasks since they're weakly linked. If the
resource feels that they want to complete the tasks out of order, I just
re-order it the way they need to get it done. This is almost as if you
would start working on assembling the roof while you wait for more woods to
arrive for the completion of the wall, once you complete the wall, you can
finish up on the roof and assemble the house...

If you can suggest how I can make sure the resources are utilized

correctly without linking sequential tasks, please let me know. I am
anxious to learn any new concepts.

 

[Jan De Messemaeker]

Hi,

Allow me to add my 2 cents worth - I am a fan of leveling

- It is definitely feasible, I have seen far bigger calculations (it won't
always be done in a millisecond though)

- There is no problem to give the same priority to different tasks, Project
will then look at ither priority items to decide which goes first. So there
is no limit of 1000

- Speaking about Project's calculation, it calculates an aggregated number
in which the priority you indicate is only one term; itis possible that a
task with a priority of 449 will be scheduled after a tak with priority 451
for instance.

HTH


--
Jan De Messemaeker
Microsoft Project Most Valuable Professional
http://users.online.be/prom-ade/index.htm
32-495-300 620

Steve,

Thanks. I never knew that Project can do this.

Would you expand on "used very sparingly"? I manage a very large team of

SW engineers and they are all on this schedule. Managing the dependencies
has been a nightmare - it doesn't help when they switch tasks around all the
time. However, with this method, it seems that I just tell Project to
"level" the whole project (2000+ tasks) each time I receive status from the
engineers and everything would just calculate - right? Since Project allows
up to 1000 priorities, it seems to me that I can prioritize 1000 tasks per
resource in any given project, right? BTW, I am currently using MSP2003.

If this Priority/Leveling method is not feasible for such a large

implementation, would you recommend another method? Thanks!