Critical path Analysis Flashcards
What is the precedence table
How to make the precedence tables
This a table to show each activity and what they depend on (what must be com0leted first) for that activity ti continue )
Make a chart with activities on left and dependence on right
How to SIMPLIFY precedence tables
Basically if it says something like G depends on all, think of activities that if you included means you don’t have to include another, because one DEPENDS on another
Basically if it says all, add all activities that ARENT present in the precedence’s before
How to convert the precedence table into an ACTIVITY NETWORK
Label each new node , starting from 0 of the sink
1) MUST have a source and sink node.
2) things that don’t depend on anything come out of sink
3) try make as straight and not overlap as possible, but if can’t it’s okay
What does a dummy activity hold value waive and what does it do
It holds 0
It just connects nodes together which would otherwise be impossible to connect
When making an activity network, what should you aim to do FIRST to avoid mistakes?
Always try do the activities that depend on ONE THING ONLY first, otherwise it might be impossible to do
Then try do those depend on 2 ONLY
You’ll find this way you won’t make mistake with dummy variables
What does an activity network allow you to model
Basically tasks, and their durations , what depends on each other
You can see which tasks must be done on time to avoid the overall project form running late etc, snd which tasks have more freedom when to be completed
How to do FORWARD PASS to find Early times
whatever the number is, add the arc weight to it
2; next compare all options, and when a decision must be made PICK THE BIGGEST SIZE CHOICE
(This because for that event to pass, all other activities must at least pass, so you know to pick the biggest earliest time to accommodate for everyone Else)
How to do BACKWARD PASS to find all the late START times
First the LAST BOX IS DUPLICATED
- subtract this time when going back in weights
- only make a choice if you have all backward pass OPTIONS AVAILABLE TO YOU
- when making a choice, pick the EARLIEST TIME
(This because if you pick a bigger time, then an activity will be missed as you went past it’s deadline)
When done the forward and backward pass, what should look like and how to find CRITICAL ACTIVITIES AND PATHS
What is a critical path even show
First should be 00 and last same same
- critical activities are those with the same early and late start
- critical path is where two critical activities are connected EXACTLY by the weight in between
This means this activity must start at this and end at that time, else whole project overload
How ti find overall critical path
critical vs non critical?
Just connect all other critical paths up
2) Remember critical paths are activities that must start and finish at certain times else project is late
Whereas non critical paths have some room to FLOAT
3 types of float
Total
Independent
Interfering
How to work out total float
Late finish - early start - duration
Or OUTER - outer - duration
(This bevause the total length is subtraction of outer, but actual wriggle room in thr slider is given by subtracting from the weight too)
What is the INDEPENDENT FLOAT
How to work out
What happens if answer is less than 0?
1) independent float is the amount of float activity can do without causing any other activities to start late or finish earlier
(For example if I finish late, then the next activity can’t start earlier )
2) INNER - INNER - DURATION
if less than 0, then = to 0
What is the interfering float and how to calculate
This is the float that WILL cause neighbouring activities to be forced to start and finish differently
Would = total float - independent float
What is the total independent and interfering float for critical activities
00 and 0
How to make cascade / gannt chart
Critical paths
- non critical path activities + how to show the float
1) time on x axis till max time
2) ANYTHING THAT IS CRITICAL PATH, CONNECT IT
- start with early start time, then make box length of duration
- connect each critical path together as next will start after lentgh of duration
3) Anything that ISNT critical takes a row each by itself and goes above
- again start early start, make width duration and MAKE DASHED BOX UNTIL LATE FINISH TIME= this represents the total, float
How to show MULTIPLE CRITICAL PATHS
First critical path = first row
Second one goes on top, and here include all activities that weren’t INJTALLT IN FIRST ROW CRITICAL PATH
How to make resource histogram from giant chart / without
Gang chart = act like gravity has dropped each thing down
ITS SUPPOSED TO SHOW AMLUNT IF WORKERS REQUIRES EACH DAY basicallt , so yh might need to adjust if certain activities take more workers
What does resolute historysm show you and what can you do by fiddling around
It shows that if you delay an activity to another day maybe, then maybe overal you’ll only need less workers to complete whole project which is goooood
For finding floats of non critical activities, how to identify what to pick
First what to do
Circle the whoel activity and then do it on thr two arcs connecting this (even if THEY HAVE CRITICAL THINGS IN THEM)
Identify critical activities first , then get rid of them
What is often an assumption when modelling days etc for duration?
Thst all the activities take a WHOLE NUMBER amount of days
Remember what are the definitions of early and late start time
Earliest and latest time whole activity can start without affecting the overall PROJECT LENGTH
What can an activity interfering with other activities do
Can ALLOW them to start later if it itself starts later, or force something to finish earlier
What is critical activity and path significance to whole project again
Thus how can you change the overall length time if you could change an acitivityn
IMPORTWNT WHAT TO LOOK OUT FOR
These are activities that must start and finish at set times or thr whole activity will overrun, so they are decisive ones
If you could change an activity , then pick the one in the critical path as these affect the whole length of project.
- IN PARTICULAR IF THERE ARE MORE THAN ONE CRITICAL PATH, PICK THR ACTIVITY THAT HOPEFULLY FALLS UNDER BOTH PATHS, so that changing this will change both paths which thus change the length of project
How to draw cascade properly after experience
Do the critical
Then everything else goes in ALPHABETICAL ORDER downwards from top
And make it easier for yourself, instead of calculating floats just check Kate time and mark it using the x axis be really quick
How to show or check if whole project can be completed by 2 workers three workers etc
Calculate time of whole tasks combined
Then the whole project length (because this is the max that if you fit each activity perfectly the duration a worker will spend )
Now multiply project length by workers and see if that first the total amount of time the task is
If they increase length time of the project how to find routes to finish the project with less workers?
The start times should add up to the project time exactly, that’s how you can manipulate
So if project time now 56, need two routes with workers starting directly after each other that will add clean to make 56
HOW TO FIND THE LONGEST AND SHORTEST ROUTE FROM A TO B OF A NETOWRK
IMPORTANT
Longest = forward backward pass method, will give the length time which equal to LONGEST LENGTH, and the paths are the critical pathways
Shortest = USE DIJKSTRA method to get length and path. The path to B will clearly be visible !!!!
