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142 RESOURCE LEVELING, GAMES OF CHANCE

system first looks at the precedence and imposed date results (the CPM sched-
ule) and then the ranking factors. There is no sure way of telling (in advance)
which ranking criteria will produce the shorter or smoother schedule. (Those 30
seemingly random numbers mentioned earlier came from running the same test
project on 13 programs. Those programs that allowed the setting of preferred
ranking criteria gave several different answers, depending on that setting.) Exper-
imentation, with varied ranking factors, is necessary in order to get close to the
best solution. In addition, in the serial method, the ranking criteria are used only
when a task is first considered for resource scheduling. The tasks are not re-
ordered during the process.

Even with the multiple options for advanced resource leveling, available in
P/2, PSDI, in that 1981 document, advised that the system is not designed to
achieve the optimal results. In addition to the demand on computer resources,
they suggested that the process needs to be timely and dynamic. Today, two
decades later, that reasoning is still valid, and, with the universal use of the serial
method, optimization cannot be expected.

We cannot, within this book, hope to resolve all the issues of efficient and ef-
fective resource leveling. We will endeavor, however, to make you more aware of
the realities of resource leveling, and of the capabilities and limitations of the
popular project management software products, with regard to resource leveling.
Perhaps as a byproduct, we will keep the heat on ourselves and the software de-
velopers to make resource leveling a more useful function than it is today.

Place Your Bets: A Review of Resource Leveling Results

Looking at the results of resource leveling tests performed on 13 project manage-
ment software products, it is startling to realize the range of answers obtained,
and the effect on project duration and resource utilization. Here is an overview.

Test model A (producing the results that were mentioned earlier) consists of
14 resource-loaded tasks, requiring either 1 or 2 units of a single resource. There
is a total of 30 MDs of effort. The unleveled CPM is 11 days. Leveling, with 2
units of the resource available, should be able to produce a 15-day schedule. Yet,
in 30 trials (without invoking splitting options, where available), only 1 iteration
produced the 15-day result. Others ranged from 16 to 20 days. (Splitting options,
available on 6 of the programs, produced schedules of 15 and 16 days. However,
activity splitting was not necessary to obtain a 15-day result via manual leveling.)

Let’s say that you are the project or resource manager on this job. Would you
be willing to pay for 40 days of effort (20 days for 2 people) when you could get
the job done with 30 days of effort?

Test model B consists of 7 tasks and 2 resources. Unleveled, the CPM duration