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CS604 - Operating Systems - Lecture Handout 16

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Summary

  • Scheduling algorithms

Why is SJF optimal?

SJF is an optimal algorithm because it decreases the wait times for short processes much more than it increases the wait times for long processes. Let’s consider the example shown in Figure 16.1, in which the next CPU bursts of P1, P2, and P3 are 5, 3, and 2, respectively. The first Gantt chart shows execution of processes according to the longestjob- first algorithm, resulting in the waiting times for P1, P2, and P3 to be 0, 5, and 8 times units. The second Gantt chart shows execution of processes according to the shortest-job-first algorithm, resulting in the waiting times for P1, P2, and P3 to be 0, 2, and 5. Note that the waiting time for P2 has decreased from 5 to 2 and that of P3 has decreased from 8 to 0. The increase in the wait time for P1 is from 0 to 5, which is much smaller than the decrease in the wait times for P2 and P3.

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CS605 - Software Engineering II - Lecture Handout 44

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Capability Maturity Model Integration (CMMI)

Capability Maturity Model or CMM is a reference model of mature practices in a specified discipline, used to assess a group’s capability to perform that discipline. In fact there are a number of CMMs. They differ by discipline (software, systems, acquisition, etc.), structure (staged versus continuous), how maturity is defined (process improvement path), and how capability is defined (institutionalization). Hence “Capability Maturity Model®” and CMM® are used by the Software Engineering Institute (SEI) to denote a particular class of maturity models.

Software CMM, the one we saw earlier on, is one of the many CMM models.

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