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Resources Histograms (RHs)

​Possible criteria:
 
  1. Minimum time
  2. Minimise total cost (this may change minimum total time)
  3. Make maximum use of resources (e.g. schedule for a fixed number of people)
 
Example:
 
Below, you can see an organised Cascade Diagram.  The numbers in brackets represent the number of workers required to complete each activity.
Picture
​Ignoring the numbers in brackets - if it was only one worker per activity, we can see you would need 3 workers to complete the project in 17 time units.
 
The RH for the case where there is only one worker per activity looks like this:
Picture
​As you can see, a resources histogram displays how many of our resources, y, are being employed at a particular time, x.  From the Cascade Diagram we can see that all three workers are working until the time of 8, where one stops.  This means that only workers 1 and 3 (2 resources) are working until time unit 13, where worker 3 stops and worker 2 starts – but we still have 2 resources employed (they just switch).  At time unit 16, worker 2 stops again, while worker 1 continues (1 resource) until time unit 17.
 
Now, using the information given in brackets showing how many workers are required per activity, our resources histogram looks a lot different.  In order to complete the project in the same amount of time, our resources histogram would look like this:
Picture
​You can see that we now need 7 people to complete the project in the given time.  To form this RH, we use the Cascade Diagram above – look at each interval and see how many resources need to be employed within that time frame.  E.g. in the 0-1 interval, we are carrying out A (2 resources), B (1 resource) and C (1 resource) at the same time – so we need 4 resources to be employed (2+1+1).  Continue like this for each interval to form the RH.
Picture

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