Critical Path Method

Hi All.

Below are some concept which Primavera use in their product



The critical path is a series of activities that determines a project’s completion time. The duration of the activities on the critical path controls the duration of the entire project; a delay to any of these activities will delay the finish date of the entire project. Critical activities are defined by either the total float or the longest path in the project network.



When you choose to calculate a schedule, all activities in the network are examined, beginning with the first and ending with the last, to calculate the earliest start and finish dates for each activity.





The activities are then reexamined in a backward pass, beginning with the latest early finish of the last activity in the network and ending with the first activity, to calculate the latest start and finish dates for each activity.





Float values are calculated using the duration and calendar definitions for the activity.

Hi karim / Dieter,



Negative float do come around in the program because of end-date constraint, but then, how do you handle it. for an activity of 7 days, if you negative float of 8 days, then actually there is no time left to do the job. Upto what extent do you follow this updated program.



just to know, cross-cultural practices round the world?



Cheers,



Rav

yes Dieter, either (o) or (-ve) it is less than 1 which will make the activity critical and fall on the CP.

Hi Karim

In P5/P6 a mandatory constraint always results in Total Float = 0. So in your example this activity is critical. If the data date is later than the constraint, TF will become negative.

Regards

Dieter

@ Mark,



You can define the critical activities either to:

1- Have a total float less than a certain value (normally 1).

2- The longest path.

Critical activities define the CP.



When u set a mandatory (must) start/finish constraint on an activity and the data date became later than the constraint date, the activity (if not started/finished) becomes critical (ie. having a TF less than 1).

Thus it becomes on the critical path.



Regards,

Karim

Yes, all activities having TF less than or equal to zero are critical activities.



You can specify the cut off value by going to Tools --> Options --> Critical activities, to define the critical path.



In P3, there is one more terminology used -- LONGEST PATH.



LP considers d activities on the longest path in the network. It is mainly used for multicalender projects, as it identifies activities that have an early finish equal to latest calculated early finish for project.



Cheers,



Rav

>Activities on the CP have 0 total float



Not quite true. If you have entered a target complete date (or a mandatory date)then this could have a negative TF and the most negative is the CP.

Hi Ranganathan,



After presenting & determining the schedule model (logic) (using ADM, PDM, ..), u use(CPM, PERT, ...) to analyze it.



CPM determines the longest path of the network (aka The Critical Path) as well as the early/finish start & finish dates of the activities.



Early dates are calculated by a method called Forward Pass.

Late dates are calculated by a method called Backward Pass.



The Critical Path is the longest duration path in the schedule, any delay to activity(s) in the CP will delay the completion date of the project.

Activities on the CP have 0 total float (this is the time that an activity can delay without delaying the project completion date), total float can be determined by 3 ways as follows:

1- Start float (LS - ES)

2- Finish float (LF - EF)

3- Longest Path



HTH.



Regards,

Karim

Ranga,

Try inputting ’critical path method’ to Google and you’ll get the answer.