make task depend on the shortest of two tasks

[Alexandra]

Hello,

I have tasks X, Y and Z.
X takes 2 estimated days (from day 1 to day 2) and Y takes 3 estimated dates
(from day 1 do tay 3).
Then I want to make task Z depend on those two tasks, in a way that it
starts when as soon as the one of them finishes, but if I do one simple FS
dependency, it will start on day 3 because it starts on the day that the
longest task finishes. Is there anyway to make it start on the day the
shortest task finishes?

Make it an OR dependency instead of a AND ?...

Thank you

 

[Jan De Messemaeker]

Hi,

The exact way you ask for it, no, unless you do some VBA programming.
But if you explain the background behind this (Why, how is it possible that
a task can begin when a link is not satisfied?) maybe I can suggest a
different approach altogther.
Greetings,

 

[Alexandra]

Thank you, Jan, for your reply.

Well, let's just say, for example sake, you have two business parters on a
sort of a contest, the first one to deliver an implementation plan wins the
contract.

task X is "implementation plan from supplier 1"
task Y is "implementation plan from supplier 2"
and task Z is "begin implementing" or "choice of supplier" or something like
that.

of course, if it's just a day's difference, it's not very important, but if
it becomes a month's difference, then it might be considerable and I might
want to reflect that in my plan...

 

[Jan De Messemaeker]

Hi,

Well to be honest I was hoping a real life example would allow me to
rephrase the whole thing but if you give me this theoretical example, the
problem stands.

There is no automatic way to do that in Project. In fact, the network
scheduling theory defines a link as something that has to be finished before
something else can start (mostly because the successor task uses the result
of a predecessor task), and that is how links in Project work.

So you cannot use links in Project; you will have to defien your own type of
link, put it in a Text field for instance, and program a VBA procedure to
calculate the constraint that will position the successor task.

An alternative might be to duplicate the poart of the schedule following the
choice, one schedule for each of the potential winners, and delete the
schedule for "the loser" when the decision falls.

Hope this helps,

 

[davegb]

Thank you, Jan, for your reply.

Well, let's just say, for example sake, you have two business parters on a
sort of a contest, the first one to deliver an implementation plan wins the
contract.

task X is "implementation plan from supplier 1"
task Y is "implementation plan from supplier 2"
and task Z is "begin implementing" or "choice of supplier" or something like
that.

of course, if it's just a day's difference, it's not very important, but if
it becomes a month's difference, then it might be considerable and I might
want to reflect that in my plan...

Beyond the issues of implementing this scenario in Project, does your
management see that this way of doing business is practically begging
the managers/suppliers to simply fabricate an early end date, win the
contract, then later, when it's too late for you to change suppliers,
notify you that they aren't going to make it? In my experience, this
is a chronic problem, particularly with some vendors, to give
optimistic delivery dates to win the contract, then change the date
down the road. This is just begging someone to pull a fast one on you
and leave your companay/team with egg on it's face.

Hope this helps in your world.

 

[Alexandra]

I understand...
I thought about that solution, duplicating the tasks following from each
option, but that just doesn't make much sense, practically and conceptually
and besides it would screwup the intire scheme, I'm using EPM and the people
whould have twice the work on their timesheets... just too messy!

Thank you for your help

 

[Alexandra]

Well, thank you for your kind advice.
First of all, it was just an example, although I've seen it happen before.
Second of all, usually I define penalties in contracts so nobody pulls fast
tracks on me nor puts anything on my face...

 

[davegb]

Well, thank you for your kind advice.
First of all, it was just an example, although I've seen it happen before.
Second of all, usually I define penalties in contracts so nobody pulls fast
tracks on me nor puts anything on my face...

LOL! Glad to hear it. Sounds like you've got it covered.

 

[Jack Dahlgren]

I've written a vba macro which does this.
Look at the "Follow earliest predecessor" macro on this page:
http://masamiki.com/project/macros.htm
It inserts negative lag on a task so that it can start as soon as the first
of its predecessors completes.

-Jack Dahlgren

 

[Mike Glen]

Hi Alexandra,

For my contribution, I would model this by making Z task FS with both X & Y.
In this way I would be modelling a worst case scenario. When either X or Y
actually finishes, just delete the other and I'm home and dry

Mike Glen
Project MVP

 

[Alexandra]

That's wonderful!! But tell me, it allows me to choose which dependencies I
want to follow the earliest taks and which ones i want to behave in the
normal way, right?...

 

[Jack Dahlgren]

Alexandra,

Select a task and run the macro.
It only works on the task you have selected.
It could be modified to work on a larger selection of tasks or all tasks,
but right now just does one at a time.

To use it effectively I'd create a new toolbar button and assign the macro
to it. Then you can select a task and click the button.

-Jack