Introduction to Resources Allocation
Projects compete with one another for resources
• consumed (e.g., materials)
• non-consumed (e.g., equipment)
Goal of resource allocation is to optimize use of
limited supply
Allocations requires making trade-offs
• time constrained … completion by a fixed time
• resource constrained … limited budget or resource
Solution to Allocate Scarce Resources
1. The Critical Path Method
Normal duration estimates
Normal costs
Crash duration estimates
Crash costs
Crash cost per day
2. Fast Tracking
An Example of a Normal/Crash Project
* Partial crashing allowed ** Partial crashing not allowed
The activity slope or cost per day is:
Crash Cost - Normal Cost
___________________________ Normal Duration – Crash Duration
Crashing a Project
Two key principles:
o Focus on the critical path(s) when trying to
shorten the duration of a project
When shortening a project’s duration, select the
least expensive way to do it
A PERT/CPM Example of Crashing a Project, AOA Network
CPM Crash Cost-duration History
Fast-Tracking a Project
Fast Tracking - an expediting technique in which
one phase of the project is started before preceding
phases are completed
Used in the construction industry when the
building phase is started before the design and
planning phases are complete
This technique is particularly appropriate when
large proportion of work is routine
Resource Loading
Resource loading refers to the amounts of specific
resources that are scheduled for use on specific
activities or projects at specific time
It is usually presented in the form of a list or table
Project Plan and Gantt Chart for Production of a Short Documentary Film
Gantt Chart for DVD Project, Adjusted for Client Availability
Table 6.2 shows the schedules for several of required resources
Resource Loading Chart for DVD Production
Dealing with the Charismatic VP Problem
Subordinates have a hard time saying "no" to a well
liked boss which can lead to overcommitted
subordinates.
Problem further compounded because more
experienced workers tend to be most over worked.
One solution is to set specific limits on amount of
overscheduling permitted.
Resource Overallocation Report for Scriptwriter Showing All Activities
Resource Leveling
Graphic Resource Allocation Report for Scriptwriter
Resource Leveled Report for Scriptwriter Showing All Activities
Graphic Resource Leveled Report for Scriptwriter
Daily Resource Loading Chart for DVD Project, Scriptwriter Leveled
Final DVD Project Gantt Chart Schedule, with Two Scriptwriters and Producer Leveled
Resource Loading/Leveling and Uncertainty
28,282 Hours Needed
Group Capacity • 21 (people) 40 (hours/week) 34 weeks = 28,560
labor hours
Correction for Holidays • 21 (people) 3 (days) 8 (hours) = 504 labor hours
Vacations • 11 (people) 2 (weeks) 40 (hours) = 880 labor hours
Resource Loading/Leveling and Uncertainty
continued
Hours Available • 28,560 - 504 - 880 = 27,176
• about 1100 less than needed
• Workload = 28,282/27176 = 1.04
Additional Problems • Workers getting sick
• Task not ready when worker is ready
• Change orders
Thirty-Four-Week Resource Loading Chart for a Software Engineering Group
Use of Project Software
Begin with PERT/CPM Schedule
Examine activities period by period and resource by
resource
If the demand for a resource exceeds supply, the
software consider the tasks one by one ….. resources
assigned to these tasks according to the priority rule
selected by the project manager
Allocation Priority Rules
As soon as possible
As late as possible
Shortest task duration first
Minimum slack first
Most critical followers
Most successors
Most resources first
ALLOCATING SCARCE RESOURCES TO PROJECTS
Criteria of Priority Rules
Schedule slippage • amount project or set of projects delayed by application
of a leveling rule
Resource utilization • extent to which resources are over or underworked
In-process inventory • amount of unfinished work in the system
ALLOCATING SCARCE RESOURCES TO
SEVERAL PROJECTS
Pseudoactivities
Pseudoactivities are those which have duration but
require no resources
The use of pseudoactivities allows a set of projects
to be linked and dealt with as though it were a
single project
• use of MSP’s resource loading and leveling charts
and tables
Multiple Projects Connected with
Pseudoactivities Shown on a Time Line
Impact of Resource Allocation on the Two Types of Project Life Cycles
Project Issues/Problems
Issues that trouble people about working on
projects regardless of type of project
• unrealistic due dates
• too many changes
• unrealistic budget
These issues/problems relate to the need to make
trade-offs
To what extent are these problems caused by
human decisions and practices?
Three Project Scenarios
Project Completion Time Statistics Based on Simulating Three Projects 200 Times
Scenario 1 Scenario 2 Scenario 3
Average 50.4 51.9 53.4
Std Dev 7.1 6.3 5.3
Max 69.4 72.7 69.3
Min 30.1 36.1 39.3
Median 50.0 51.8 53.1
Key Observations
Average completion times
Implications of assuming known activity times
Shape of the distribution
Worker time estimates
Impact of inflated time estimates
Student syndrome
Multitasking – Two Small Projects
Alternative Gantt Charts for Projects A and B
Common Chain of Events
Assuming that activity times are known and that
the paths are independent leading to
underestimating the time needed to complete the
project
Project team members inflate time estimates
Work fills available time
• student syndrome
• early completions not reported
Common Chain of Events continued
Misused safety time results in missed deadlines
Hidden safety time complicates task of prioritizing
project activities
Lack of clear priorities results in poor multitasking
Common Chain of Events concluded
Poor multitasking increases task durations
Uneven demand on resources may also occur as a
result of poor multitasking
More projects undertaken to ensure all resources
are fully utilized
Adding more projects further increases poor
multitasking
Reversing the Cycle
Reduce number of projects assigned to each
individual
Schedule start of new projects based on availability
of bottleneck resources
Reduce amount of safety time added to individual
tasks and then add some fraction back for the entire
project, called the project buffer
The Critical Chain
Think in terms of the longest chain of consecutively
dependent events
• consider both precedence relationships and resource dependencies
Project buffer
• added safety time for the entire project
Feeding buffer
• safety time added to chains other than the critical chain
because the network’s paths often lead into or merge with
the critical chain
Project and Feeder Buffers
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