Start to Start - Does not always force tasks to start simultaneously

[davidd31415]

Is there a way to force two tasks to start simultaneously?

I've found that with MSP2000 Start-to-Start only works when one of the two tasks starts later than the other; if this is reversed then they do not start simultaneously.

If I could enter the start-to-start dependency into both tasks I'd be all set but it appears this is not possible. Is there another way to make them start simultaneously?

 

[PDQBach]

SS always starts two tasks simultaneously -- unless you have imposed a constraint on one of the tasks. The task you are having problems with almost certainly has a SNET constraint (caused by entering a specific Start date).

 

[davidd31415]

Both tasks also have a FS dependency, I'm guessing that is causing the issue?

The only way I have been able to get the two tasks to start simultaneously is to manually locate the task that is starting earlier and add the SS dependency to it. This is fine unless if the task I did not add a dependency to ends up starting earlier.

 

[PDQBach]

A task always starts after all predecessor tasks have finished (makes sense when you think about it).

I'm not sure why you are having difficultly with the tasks and the SS dependency.

As a standard practice you should never enter start or finish dates. The start date is determined by the finish of the predecessor (in an FS relationship) or by another task's start (in an SS relationship).

The finish date is determined by the Start + duration unless you have imposed other constraints (Must Finish On, for example).

 

[davidd31415]

I often use multiple FS relationships on a task to make sure it starts only after multiple tasks have finished.

I thought I could use a FS and SS together to make sure that a task starts only after the FS tasks have finished and when the SS task starts. From what I've seen this only works when the task with the SS dependency starts earlier than the task it has the SS relationship with. If I could add an SS dependency to both tasks things would work great. I'm thinking maybe I can work something out with a milestone or third task, I'll let you know.

 

[davidd31415]

Sure enough, using a milestone did the trick. I'll try to quickly explain what I'm doing here...

Start with 4 fixed duration tasks, Task A, Task B, Task C, Task D. Set the following durations:

Task A: 2d
Task B: 1d
Task C: 5d
Task D: 1d

Set Task B's predecessor to be Task A FS.

Set Task D's predecessor to be Task C FS.

Now add a Task B predecessor as: SS with Task D.

Now change Task A duration to 5 days and Task C duration to 2 days. Tasks B and D no longer start at the same time!

My fix for this is:

Remove all predecessor relationships from Task B and Task D.

Create a milestone called Milestone A. Add Task A and Task C as FS predecessors to Milestone A. Next add Milestone A as a FS predecessor for Task B. Do the same for Task D. Tasks A and D now start at the same time.

I'd love to know of a less messy solution but at least this works.

 

[PDQBach]

When I follow your steps, no milestone is necessary - B and D both start at the same time.

Tools | Options | Calculation-tab ... is calculation mode set to automatic?

Project | Project Information ... is Scheduled start from showing "Project Start Date" or "Project Finish Date"?

The functionality you are having problems with is so fundamental that it has to be something else you are doing.

 

[davidd31415]

I read through my steps and performed them again to check for typos- same results now that I'm at home with MSP2003.

Calculation is set to automatic on the calculation tab.

Scheduling is set to start from Project Start Date.

I would be questioning my install of MSP if I didn't get the same results at work and home on two different versions.

Any other ideas?

 

[Prothios]

I just ran through those same steps (save the steps to 'correct');

1. Calculation is set to automatic
2. Scheduling is from Project Start Date

I have the same effect that is described, but to me it makes sense. The predecesessor relationship of SS means that (in this case) that task B is linked to the start of task D. It does not say they must start at the same time, just that the start of task B is influenced by the start of task D;

In a not-so-perfect analogy (i'm not in construction) - task A is the framing of the house including stairwells, task B is showing the house, task C is planting trees, task D is putting the final landscaping in (mulch, etc). You can show the house, but you want to have the main structural items in place - but you don't care if the mulch is down because that is just a nice-to-have. If the trees are not in, nor you cannot walk through the rooms, you cannot show the house.

Hope that helps!

 

[PDQBach]

This is really starting to frustrate me! <grin>

This is a "part way through" file. I just want to confirm that I have interpretted your instructions correctly.

**begin
ID,Name,Duration,Constraint_Type,Constraint_Date,Start_Date,Predecessors
1,A,2 days,As Soon As Possible,NA,05-15-07 8:00,
2,B,1 day,As Soon As Possible,NA,05-22-07 8:00,"1,4SS"
3,C,5 days,As Soon As Possible,NA,05-15-07 8:00,
4,D,1 day,As Soon As Possible,NA,05-22-07 8:00,3
**end

Watch out for line wrap. There should be 5 lines: a header and 4 task lines.

1. Copy those and paste them into a .txt file (use Notepad). Let's call the file Step1.txt

2. Create an Excel Spreadsheet.
2a. Start Excel
2b. File | Open
2c. Change "Files of type" to "All Files (*.*)"
2d. Navigate to the folder where you saved Step1.txt
2e. Open that file
2f. You may get an error message saying it is SYLK file but cannot be loaded. Click on OK
2g. You will see the Import Wizard popup.
2h. Click on "Delimited" (probably already selected; just making sure)
2i. Click on "Next"
2j. Click on the box labelled "Comma"
2k. Click on "Finish"
2l. Click on File | Save As ...
2m. Navigate to the folder where you want to save the file
2n. Change "Save As type" to "Microsoft Office Excel Workbook (*.*)"
2o. Change the filename to Step2.xls
2p. Click on Save
2q. Exit from Excel.

3. Start Project
3a. File | Open
3b. Change the "Files of type" to "Microsoft Excel Workbooks (*.xls)"
3c. Navigate to the folder where you saved Step2.xls
3d. Open that file. That will start the import wizard
3f. Click "Next"
3g. Click "New map" (probably already selected, just making sure)
3h. Click "Next"
3i. Click "As a new project" (probably already selected, just making sure)
3j. Click "Next"
3k. Click "Tasks"
3l. Click "Next"
3m. Click on the dropdown for "Source worksheet name" and select the file. This should populate the "Verify or edit" table data just below it.
3n. Click "Finish"

The indicator column (it has a lower case "i" in a blue circle) should be blank.

You should see the project file that you have just before your instruction "Now change Task A duration to 5 days".

If this file and your file are not the same, please indicate what changes I need to make.

 

[Prothios]

PDQBach,

I followed your instructions - but still get the same thing as described by David.

The key is that Task B has two predecessor relationships - so the latest task (Task A finish or Task D start) is what sets the start of Task B; To quote the evilest phrase to ever frustrate users "Works as designed".

 

[PDQBach]

But it is WAD and it is, actually, working exactly the way it should (and the way a scheduler should want it to).

First of all, there appears to be a misunderstanding of what SS means. SS means the Primary task MUST start before the Dependent task MAY start. In PMI terminology, "The logical relationship where initiation of the work of the successor schedule activity depends on the initiation of the work of the predecessor schedule activity."

SS does not mean that both tasks MUST start at the same time.

In order to configure this series of tasks the way you seem to want, you should change the Predecessor field for task B to "1" and change the Predcessor field for task D to "3,2SS".