CSC309 Lecture 03

Software Engineering II
Software Metrics: Code Quality
(202404)

Transcript

1. jgs CSC 309 Software Engineering II Lecture 03: Software Metrics: Code Quality Dr. Javier Gonzalez-Sanchez javiergs@calpoly.edu www.javiergs.com Building 14 -227
2. jgs Previously …
3. jgs Javier Gonzalez-Sanchez | CSC 309 | Winter 2023 | 3 § Knowing what is inside your source code is the first step in assessing the quality of the software product. § Knowing the quantity of work performed in generating the source code is the first step in determining the productivity of your software team. Software Metrics
4. jgs Javier Gonzalez-Sanchez | CSC 309 | Winter 2023 | 4 code Key Ideas CSC 309 idea requirements architecture design quality measure
5. jgs Javier Gonzalez-Sanchez | CSC 309 | Winter 2023 | 5 Stable Abstraction Principle Abstract concrete Stable Hard to Change Only incoming dependencies Unstable Changeable Only outgoing dependencies
6. jgs Software Metrics Size
7. jgs Javier Gonzalez-Sanchez | CSC 309 | Winter 2023 | 7 Metrics Size LOC eLOC lLOC Understandability Comments Whitespaces Complexity Average, Max, Min LOC Interface Complexity Cyclomatic Complexity Software Metrics
8. jgs Javier Gonzalez-Sanchez | CSC 309 | Winter 2023 | 8 § LOC – Lines of Code Metric. Including lines of a single brace or parenthesis § LOC are used to create time and cost estimates. § LOC are a tracking tool to measure the degree of progress on a module or project. § An experienced developer can gage a LOC estimate based upon knowledge of past productivity on projects. Size Metrics
9. jgs Javier Gonzalez-Sanchez | CSC 309 | Winter 2023 | 9 § eLOC – effective Lines of Code Metric. Only code statements § An effective line of code or eLOC is the measurement of all lines that are not comments, blanks or standalone braces or parenthesis. These can inflate LOC metrics by 20 to 40 percent. § This metric more closely represents the quantity of work performed. Size Metrics
10. jgs Javier Gonzalez-Sanchez | CSC 309 | Winter 2023 | 10 § lLOC – logical Lines of Code Metric. § These statements are terminated with a semi-colon. § The control line for the "for" loop contain two semi-colons but accounts for only one semi colon. Size Metrics
11. jgs Javier Gonzalez-Sanchez | CSC 309 | Winter 2023 | 11 Example
12. jgs Software Metrics Complexity
13. jgs Javier Gonzalez-Sanchez | CSC 309 | Winter 2023 | 13 § Cyclomatic Complexity. It is a quantitative measure of the number of linearly independent paths. § Paths occur when "while,” "for,” "if,” "case," and "goto" keywords appear within the function. § If the source code contained no control flow statements (conditionals or decision points), the complexity would be 1 § If the code had one single-condition IF statement, there would be two paths through the code: one where the IF statement evaluates to TRUE and another one where it is considered to be FALSE. § Two nested single-condition IFs, or one block with two conditions, would produce a complexity of 3. Function Metrics
14. jgs Javier Gonzalez-Sanchez | CSC 309 | Winter 2023 | 14 Cyclomatic Complexity CC = Edge - Node + 2 Or CC = ConditionalNodes + 1
15. jgs Javier Gonzalez-Sanchez | CSC 309 | Winter 2023 | 15 i = 0; n=4; while (i<n-1) { j = i + 1; while (j<n) { if (A[i]<A[j]) swap(A[i], A[j]); } i=i+1; } // CC = 9 - 7 + 2 = 4 // CC = 3 + 1 = 4 (Condition nodes are 1,2 and 3 nodes) // A set of possible execution path of a program // 1, 7 // 1, 2, 6, 1, 7 // 1, 2, 3, 4, 5, 2, 6, 1, 7 // 1, 2, 3, 5, 2, 6, 1, 7 Cyclomatic Complexity
16. jgs Javier Gonzalez-Sanchez | CSC 309 | Winter 2023 | 16 Complexity Number Meaning 1-10 Structured and well written code High Testability Cost and Effort is less 10-20 Complex Code Medium Testability Cost and effort is Medium 20-40 Very complex Code Low Testability Cost and Effort are high >40 Not at all testable Very high Cost and Effort Cyclomatic Complexity
17. jgs Test Yourselves
18. jgs Javier Gonzalez-Sanchez | CSC 309 | Winter 2023 | 18 Hello World
19. jgs Javier Gonzalez-Sanchez | CSC 309 | Winter 2023 | 19 BubbleSort Iterativo
20. jgs Javier Gonzalez-Sanchez | CSC 309 | Winter 2023 | 20 Recursive BubbleSort
21. jgs Javier Gonzalez-Sanchez | CSC 309 | Winter 2023 | 21 In Order Traversal
22. jgs Javier Gonzalez-Sanchez | CSC 309 | Winter 2023 | 22 Example
23. jgs Javier Gonzalez-Sanchez | CSC 309 | Winter 2023 | 23 Example
24. jgs Javier Gonzalez-Sanchez | CSC 309 | Winter 2023 | 24 Example
25. jgs Javier Gonzalez-Sanchez | CSC 309 | Winter 2023 | 25 Questions
26. jgs Javier Gonzalez-Sanchez | CSC 309 | Winter 2023 | 26 Chapter 24 Reference
27. jgs Javier Gonzalez-Sanchez | CSC 309 | Winter 2023 | 27 Office Hours Tuesday and Thursday 3 - 5 pm But an appointment required Sent me an email – javiergs@calpoly.edu
28. jgs
29. jgs CSC 309 Software Engineering II Lab 02: Tower of Hanoi Quality Metrics Dr. Javier Gonzalez-Sanchez javiergs@calpoly.edu Building 14 -227
30. jgs Javier Gonzalez-Sanchez | CSC 309 | Winter 2023 | 31 Step 1 Calculate Code Metrics (LOC, eLOC, lLOC, CC) Per Class for https://github.com/javiergs/TowerOfHanoi
31. jgs Javier Gonzalez-Sanchez | CSC 309 | Winter 2023 | 32 Step 2 Create a UML Class Diagram for https://github.com/javiergs/TowerOfHanoi
32. jgs Javier Gonzalez-Sanchez | CSC 309 | Winter 2023 | 33 Step 3 Calculate Structural Metrics (A, I, D) Per Class https://github.com/javiergs/TowerOfHanoi
33. jgs Javier Gonzalez-Sanchez | CSC 309 | Winter 2023 | 34 Step 4 Write a paragraph about what you think of the metrics. What do the metrics state about the code? – explain with your own words (good, bad, unknown) https://github.com/javiergs/TowerOfHanoi
34. jgs Javier Gonzalez-Sanchez | CSC 309 | Winter 2023 | 35 Step 5 Compile and run the code. You will notice an error when moving disks as follows:
35. jgs Javier Gonzalez-Sanchez | CSC 309 | Winter 2023 | 36 Step 5 repeat several times { move disk 1 from Poll 1 to Poll 3. move disk 1 from Poll 3 back to Poll 1 } // Notice how each time the disk is drawn // upper and upper like floating in the poll // Why?
36. jgs Javier Gonzalez-Sanchez | CSC 309 | Winter 2023 | 37 Step 5 Can you fix it?
37. jgs Javier Gonzalez-Sanchez | CSC 309 | Winter 2023 | 38 Step 5 How many files need to be edited? How many lines are to be added? How many lines are to be modified or removed? Elaborate an explanation (either way)
38. jgs Javier Gonzalez-Sanchez | CSC 309 | Winter 2023 | 39 Let’s Work
39. jgs CSC 309 Software Engineering II Javier Gonzalez-Sanchez, Ph.D. javiergs@calpoly.edu Winter 2024 Copyright. These slides can only be used as study material for the class CSC308 at Cal Poly. They cannot be distributed or used for another purpose.