1. West Virginia University Slide 1 Copyright © K.Goseva 2010 CS 736 Software Performance Engineering Comments on Homework #1  Please revise the solution of your Homework 1 by following the comments given on your assignment and on the following slides  Include an alternative (i.e., case node in the software execution model) to model the possibility that the borrows ID is not authorized  Reassign the software resources as needed  Correct the solution of the model  Provide the corrected software execution model with the solution of Homework 3 (to be assigned Sept 30, 2010)  If you have any questions  Stop by my office during office hours (Tuesday & Thursday 2:00 – 3:00 pm)  Send me an e-mail. I do my best to check my e-mail as often as possible and get back to you

2. West Virginia University Slide 2 Copyright © K.Goseva 2010 CS 736 Software Performance Engineering Comments on Homework #1  On the use case model  Borrower does not interact directly with the system for “check-out”, “return”, “add” or “remove book”  Borrower interacts with the “search book” use case  DB may be added as an actor or assumed to be part of the system. Either way, there should be steps for some use cases (e.g., “check-out” that update book’s and/or borrower’s records  System admin may be added as an actor (not necessary)

3. West Virginia University Slide 3 Copyright © K.Goseva 2010 CS 736 Software Performance Engineering Comments on Homework #1  On the scenario & sequence diagram  Write a scenario in some sort of pseudo code  Develop an UML sequence diagram using the standard notation  Include loop for checking-out more than one book (in our example it is assumed exactly three books)  Scanning and authorization of the borrowers card is dome only once (not for each book, i.e., it is not part of the loop)  Have to include DB as an object or as part of the ‘Library system’  May have other devices, such as card reader

4. West Virginia University Slide 4 Copyright © K.Goseva 2010 CS 736 Software Performance Engineering Comments on Homework #1  On the software execution model  Have to correspond to the sequence diagram  Follow the standard notation  On the assignments of software resources  Have to include assignment to software resources first  Include delay in steps that require response from the human or some slow, mechanical operation such as Scanning borrowers ID or Scanning book  In steps that only require computer operations delays are not needed in most cases  The other resources such as DB access or Network access will account for the slower operations

5. West Virginia University Slide 5 Copyright © K.Goseva 2010 CS 736 Software Performance Engineering Comments on Homework #1  Example for assignment of software resources  Authorize borrower’s ID needs more CPU work units than Scan borrower’s ID  No DB access is needed for Scan borrower’s ID since the DB is accessed when the authorization is done (e.g., in the Authorize borrower’s ID operation)  Delay in the Scan borrower’s ID step has to be larger than the delay (if any) assigned to the Authorize borrower’s ID since it includes human/computer interaction and slow, mechanical device  In most cases assigning delay to steps such as Authorize borrower’s ID is not needed since the slow disk and network operations usually are accounted for through software resources such as DB and Network Work unit1 DB0 Delay3 Work unit2 DB2 Delay0 Scan borrower’s IDAuthorize borrower’s ID

6. West Virginia University Slide 6 Copyright © K.Goseva 2010 CS 736 Software Performance Engineering Comments on Homework #1  On the solution of the software execution model  Do not simply sum up the values. USE THE REDUCTION RULES  Multiply the values for the steps in the loop with the number of times the loop is executed  In cases of other structures (e.g., case structure which represents alternative or optional steps) estimate best/worst/average time  Since Software execution model provides input to the System execution model, it is better to first estimate the Total for each hardware resource and then multiply with the Service times and sum  This way you will have the visit counts and service times, that is, the demands for each hardware resource. These are inputs for the System execution model.