As late as possible without affecting other tasks

[juliangall]

Is there a way to set a task so that it starts as late as possible, but without delaying other tasks?

e.g.

ID,Name,Duration,Predecessors,Constraint_Type,Constraint_Date
1,Task 1,5 days,,As Soon As Possible,NA
2,Task 2,2 days,"1,3",As Soon As Possible,NA
3,Task 3,1 day,,As Soon As Possible,NA
4,Task 4,0 days,,Finish No Earlier Than,Fri 06/10/06

Here, if I make Task 3 start as soon as possible, it starts now and leaves a gap before Task 2, its successor. If I make it start as late as possible, Task 2 then gets pushed to the right as far as Task 4 will allow. I want Task 3 to occur just before Task 2 without a gap, but I don't want Task 2 delayed.

I would prefer not to put date constraints on tasks as this makes the plan difficult to change.

Thanks for any hints or suggestions.

Julian

 

[PDQBach]

The answer to your question ("Is there a way ...") is: yes.

But the real question is mine: why would you want to do this? All you are attempting to do is make the schedule look pretty.

If you schedule everything with ASAP constraints then the difference between the Finish of Task3 and the Start of Task2 is called "slack" and represents the amount of time that you can delay the start/finish of a task without delaying the completion of the project.

A good PM focuses on these tasks so that the project can be brought in on schedule. Obviously, as tasks finish early/late, the critical path changes so the PM is constantly monitoring the schedule to focus on the critical (0 days of slack) tasks.

But, since you want to focus on the pretty schedule, the answer is to make the duration of Task1 and Task3 the same. As long as you can be certain that Task1 really will take longer than Task3 then:

Click on Task1 Duration.
Press Ctrl+C
Click on Task3 Duration.
Click on Edit | Paste Special..., click on the "Paste Link" radio button, click on OK.

You'll see a little indicator in the lower right corner of Task3 Duration. That indicates the field is linked but you cannot determine what the data source is. That information isn't even exposed in the Project object model.

 

[GretchenNeubauer]

PDQBach,

I am interested in accomplishing the same affect as Julian but for the purpose of letting the resources know the latest date that they can start their tasks without jeopardizing the schedule.

Consider this scenario...
Resource 2 is dependant on Resource 1 completing some tasks (completion date represented by a milestone). Resource 2 also has some tasks that can be completed independant of Resource 1 but need to occur before Resource 1's milestone date. I want the schedule to indicate the latest date that resource 2 can start the independant tasks such that those tasks are completed by Resource 1's milestone date (i.e. just-in-time). As Resource 1's milestone date changes (because Resource 1's tasks run longer or shorter than estimated) Resource 2's tasks should move appropriately therefore causing the latest date Resource 2's tasks can begin to move. This allows Resource 2 to know when they must start all tasks since they have other projects to "juggle". The problem is that the As Late As Possible dependancy pushes all linked tasks out (if there is any schedule slack). I don't want any tasks to be pushed out. I want all Resource 2's non-dependant tasks to link to Resource 1's milestone.

ID,Name,Duration,Predecessor,Constraint_Type,Owner
1,Task 1,2 days,,ASAP,Resource1
2,Task 2,4 days,1,ASAP,Resource1
3,Milestone,0 days,2,ASAP,Resource1
4,Task 3,1 day,3,ASAP,Resource1
5,Task 4,6 days,4,ASAP,Resource1
6,Task 5,2 days,,ASAP,Resource2
7,Task 6,1 day,6,ASAP,Resource2
8,Task 7,4 days,7 3,ASAP,Resource2
9,Task 8,2 days,8,ASAP,Resource2

The above schedule produces a 5 day gap between Resource 2's Task 6 and Task 7. I want Resource 2's Task 5 and Task 6 to "back up" against Resource 1's milestone. Kind of like a FF link with a neagative lag time the length of the task duration. If there was a way to enter a calculated value for lag time (i.e. the duration of a certain task identified by an ID) this would give me the results I need.

Thanks,
Gretchen Neubauer

 

[PDQBach]

Oh, I am going to hate myself in the morning.

Yes, you can do what you want. Yes, I will show you how to do it.

But don't do it.

1. Set a Finish-to-Start link from 7 to 3.
2. Set a Finish-to-Start link from 5 to 6.
3. Set both task constraint types to "As Late As Possible".

But just because you can doesn't mean you should.

What you've just done is eliminate any slack on Task 5 and on Task 6. That has put both of them on the critical path. If either of them is delayed then the Milestone task is delayed and that will delay the completion of the project since the Milestone is on the critical path.

I'm sure you've got very good reasons for wanting to show the schedule this way. I'm guessing that "What's the latest date Resource 2 can join the project and not delay the completion?" is probably the question you are asking.

The real question you are asking though is "Assuming that the estimates for Task 1 and Task 2 are accurate and the tasks don't finish early and assuming that the estimates for Task 5 and Task 6 are accurate and the tasks don't finish late, what is the latest date Resource 2 ..."

When you do what I've described, you eliminate slack and make your critical path more complex. If task 5 or task 6 runs late then you'll end up with Resource 1 waiting for those tasks to complete before the milestone can be achieved and, therefore, before work can begin on Task 3.

By the way, thank you for providing the data the way you did. It made it so easy for me to recreate your schedule fragment!

 

[GretchenNeubauer]

PDQBach,

Thanks for replying.

I did conjure up another way but I like yours better. My way had me calculating the duration of the tasks 5 and 6 and setting a Start-to-Start link from the milestone to task 5 with a negative lag time the length of the calculated duration.

I did change one thing in your solution. I changed the link from 7 to 3 to a Start-to-Start link (rather than a Finish-to-Start).

Good Stuff!!
Thanks again,
Gretchen