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