Beginning Software Engineering. Stephens Rod

id="x_7_i104"> Figure 3.5 After three rounds, the Start task and tasks A, F, H, and B are positioned. Tasks C and I are in the Ready pile.

By now you probably have the hang of it. Position tasks C and I, and remove them from the Pending tasks’ predecessor lists. That removes the last predecessors from tasks D, E, and G, so move them to the ready pile, as shown in Figure 3.6.

Figure 3.6 After four rounds, only the Finish task is still in the Pending pile.

      In the next round, position tasks D, E, and G, and move the Finish task to the Ready pile. Then one final round positions the Finish task.

Now draw arrows showing the predecessor relationships between the tasks. You may need to adjust the spacing and vertical alignment of the tasks to make the arrows look nice. Figure 3.7 shows the final result.

Figure 3.7 This PERT chart shows the paths of execution of the project’s tasks.

      To check your work, you can verify that each task has one arrow entering it for each of its predecessors. For example, task G has two predecessors, so it should have two arrows entering it.

       Critical Path Methods

      PERT charts are often used with the critical path method, which was also invented in the 1950s. That method lets you find critical paths through the network formed by a PERT chart.