LongestPathAs a scheduler always deal with the longest path which may I say is very popular between managers. They dont care about details or see many activities. What they want is whether the project is going to be late and see the most critical path or what I call the longest path.Longest path is the longest continuos path of a project. There are different ways to obtain this path.Forward Pass is the forward pass calculating the early dateBackward Pass is the pass calculating the late dateEarly Dates are the earliest date an activity can start or finishLate Dates are the latest date an activity can start or finishAnalyzing the following example we will create simple rules to calculate the critical longest path and its methodology.

Forward PassFirst find the early start (ES) and early finish (EF) moving forward.The calculation begins with activities without predecessors. Primavera assigns theData Date which will be Day 1.Then Primavera calculates the early finish as follows;early finish (EF) = early start (ES) + (Duration) - 1

Backward PassPrimavera assigns the latest Early Finish date calculated in the Forward Pass to Late Finish of activities without successors. Primaveracalculates late starts as followslate start (LS) = late finish (LF) (Duration) +1Total Float is determine by the difference between late finish and early finish, calculate as follows(Total Float) = (Late Finish) (Early Finish)Our final result from the example is

Free Float vs TotalFloat04 Dec 2010 Leave a Commentby civilprima in Primavera I have dealed with many managers with not idea of the meaning between free and total float. This is something that schedulers deal every day in every project. In my caseI believe that total float is more meaningful from thebroadwide project view.Lets look at theexample below

It the example the project finish date is 28-Feb-2011. ThenFree Float = Working days between the activity a its successor. The amount of time that a schedule activity can be delayed without delaying the early start of any immediately following schedule activities. Activity 3 the finish date is 07-Jan-2011. Its successor is Activity 6and the start date is 24-Jan-2011 = 10 working days.Total Float =Total float is the number of days an activity canbe delayed without delaying the project completion date. So start with the project finish date 28-Feb-2011and the Activity 6 finish date 4-Feb-2011. Total float of 16 working days. Fot the Activity 3 = 16 days + 10 days = 26 days.Conclusion. I tried to ilustrate is my own words the difference of free float and total float I hope you find it helpful.