Float Calculations on a Resource Loaded Schedule

Just copy your project to a new project and do a global change to your calendars.

Well Thanks for the reply. But I am afraid doing the change to calendar will impact the finish dates right. for example, If I have an activity taking 24 days to be done on a 6 work day calendar it is going to take 4 weeks but if I change the calendar thru global change then that is going to make the activity done by 3 weeks and 3 days. so the float generated by this method will not be accurate right. Please let me know otherwise.
Thanks,
Suresh

If you want you can also constrain finish dates to the early finish dates in the copy.

Probably the best thing to do is create a meaningful end activity such as "FIELD WORK COMPLETE" on a 7x24 calendar and constrain it with a mandatory finish. Isn’t that float value what’s really important?

P3 calculate various field base on a common field. Like plan % Complete, summary of acutal % complete, total float.

However, it is not possible to calculate float on a multi calenda activity.

Thanks to you all for coming up with suggesstions. Please keep them coming. I am still trying to figure it out.
Thanks,
Suresh

Creat a custom data item called "float", and make a global change "float = early finish - early start".

Joe

Correction :

Global change : "float = late finish - early finish"

Joe

Hi,
Thank you for your suggestion. I tried the method of Global Change. Unfortunately, what happened was the float was calcluated on a 5 day calendar and not 7 day calendar as I wanted. any other suggestions please.
Thank you,
Suresh

Suresh,
I’m not figure out the solution but think about your question. Amount of float is based on the stated formula, but which calendar it based? The activity or the successor activities or from the key linked activities?

If re-figure the float amount, is programme reader will be misunderstand?

Suresh, hope this help
Create a dummy activity in 7-d calendar to ’eat’ float. One dummy per each float. FS relationship to its associated activity.
Before claculation, OD for dummy is zero. Schedule the network. Then by gloabl change fill in start/finish dates of float to dummy activity Start on and expect finish dates constraint. The OD of dummy will be in 7-day calendar calculated float.

I think the above solution work but I cannot figure out what the pupose?

Yup.. if we use different calendar it will be make different finish date and total float......

Regards,
Berli

P3, P3e, MS Project and other software discussed on this site don’t calculate resource constrained floats at all. If you level resources using this software then the forward pass takes into consideration resource constraints and the backward pass is made without considering resource limitations. As the result calculated total float is not feasible. It shows the reserves you will have if the project resources will be unlimited.

Vladimir

Agree that we need to consider the resource when calculating float. However, if we added the resource constraint within the forward / backward pass then it will complicate the calculation. In a way that you may or may not notify where and when the resource driving the activity to longer than it original antipicated.

My usual pratice is firstly assign the pure logic / duration without any resource constraints.
Look at the resource histogram
find the period that have a peak for each individual resources (or critical resource only)and overall resource
Link the resource logic between activity.
ie two independent activities using resource 10 unit of resource / day
if resource A is only limited to 10 units / day I need to link between them and start one activity 1 first then activity 2.

And that may create a critical path within the logic network
I schedule the project again and looking at what are the possible way to increase the total float.

this excises may take sereval pass. Once finish I will then have a baseline project.

Back to the original question, it will be difficult to calculate exact float within a multi-cal project environment. Remember if you have a link between two activity pre activity have a 5 day cal and the suc have a 7 day cal what is the relationship should be ?? cal 5 days or 7 days. if the relationship is FS and the first activity finished @ Friday should the activity start on Sat since the activity can start on SAT. But the predecessor cal can only start on monday - friday. It is complicated. The software have to make a assumption which is the global cal use at all time. I guess if the software allows each relation have their own cal assign to it then a calculation base on multi-cal float can be achieve.

The question is what benefit the schedule or the project can gain by introducing all these additional variables. Remember one or variable you need one more regulation or additional causes in the spec from the clients. (Because they don’t want to give a open cheque to the contractor)

I tested my previous proposed and it work. Then I simplify some processes. Instead of dummy activities, I export the schedule result, on spreadsheet, work out the start/finish date of float. Import these value to a new P3 project with constraint start on equal to float start and constraint expected finish on equal to float finish.
Of cource, the new project is in 7-day calendar. The auto calculated OD will be your expected value.
The benefit is not confuse with current project data.

Alex,
you proposed hand made leveling that may be used only for small projects where the number of resources and activities is small. Besides the artificial links may restrict scheduling options in future when the situation in your project may change.
I agree that the scheduling software shall use not only activity and resource calendars but also calendars of relationships (lags).
If you can simulate the real life conditions then the schedule will be more reliable and less complicated.

Hi Mr. Suresh,

1. Create a custom data item "gfloat" -meaning global float
2. Export the fields for activity id, early finish, late finish and "gfloat" in a worksheet file.
3. Open the exported worksheet file in Excel or Lotus 123
4. Input the formula "late finish - early finish" (using the reference cells of course) in the field "gfloat" for each activity.
5. Convert the results to "values".
6. Save in the same file (note: extension must remain wk1).
7. Import back to Primavera.
8. You have to do this exercise everytime you make an update of the schedule.

May I stress on the formula: Float = LF - EF. This formula cannot provide the expected result since the difference is in same calendar also.

That’s why I suggest is the difference is Float start date - Float end date.

Example to support, consider a activity is OD=5; start on Fri; end on Thr; 5 wkday/wk calendar; 1D float after schedule. Standard formula will result 1, but the result may be 3 since weekend may be count in and this depends the calendar of its key successor(s).

SURESH:

==============================================
Lorenzo Cabatuando GAVE THE CORRECT PROCEDURE!
==============================================

Joe Mounsour almost got it right.
All the others were did not really know how to do it.

So do Lorenzo’s procedure and focus on it. If you have any glitches, just ask but you need to concentrate on Lorenzo’s procedure.

That’s it.

Thank you all for pouring in responses and suggestions. I am working on it and I will let you all know if it worked or not.
Thank you,
Suresh

Try exporting the early and late dates to a worksheet file the do the math within the worksheet.

LORENZO GOT IT

It would be nice if Primavera includes formula calculated fields into their products jus as Microsoft does. It would be usefull to be able to compute difference in work dates dates based on specified calendars as one of the available functions.

Jorge,
Sorry I have different view on yours. The difference calendar is the requirment.

Jorge,

Please explain a little better why the weekend in your example is important to count in a "global float" number. Wouldn’t it be dangerous to inflate the value based on the successor’s calendar?

The goal should be to ignore ALL calendar effects on the activity and "key successor". Also how do you recommend getting (exporting/calculating) the Float start date OR the Float end date?

Rafael,

Use GLOBAL CHANGE to write the formula : Float=LF-EF.

Cheers!!!

If an activity/task is based upon a 5 day work week, the float must be calculated using the same basis or you will get an incorrect answer (unless you are perfoming a what-if analysis for schedule acceleration - but then, you should probably just change the activity/task’s calendar for the analysis).

Free float should be a measure of the time an activity can slip before impacting any of it’s successors.

Total float should be a measure of the time an activity can slip before impacting the critical path.

Both of these values need to consider the working calendar for the task in question.

Bernard Ertl
eTaskMaker Project Planning Software