CSC307 Lecture 14

Introduction to Software Engineering
Metrics
(202505)

Transcript

1. Dr. Javier Gonzalez-Sanchez javiergs@calpoly.edu www.javiergs.info o ffi ce: 14 -227 CSC 307 Introduction to Software Engineering Lecture 11. Software Metrics
2. Feedback From Assignment 03
3. Code 3 https://github.com/CSC3100/App-Paint/
4. Single Responsibility • E a ch cl a ss or function should h a ve one, a nd only one, job. • Keep functions focused on a single t a sk. • Bre a k down your code into sm a ller, reus a ble modules or functions. • Ensure e a ch module or function h a s a cle a r, well-de f ined purpose. • 4
5. Clean Your Code!
6. Maven File and Directories 6
7. About MQTT 8
8. Code Metrics
9. Software Metrics Size
10. Size Metrics • LOC – Lines of Code Metric. Including lines of a single br a ce or p a renthesis • LOC a re used to cre a te time a nd cost estim a tes. • LOC a re a tr a cking tool to me a sure the degree of progress on a module or project. • An experienced developer c a n g a ge a LOC estim a te b a sed upon knowledge of p a st productivity on projects. 12
11. Size Metrics • eLOC – e ff ective Lines of Code Metric. Only code st a tements • An e ff ective line of code or eLOC is the me a surement of a ll lines th a t a re not comments, bl a nks or st a nd a lone br a ces or p a renthesis. These c a n in f l a te LOC metrics by 20 to 40 percent. • This metric more closely represents the qu a ntity of work performed. 13
12. Size Metrics • lLOC – logic a l Lines of Code Metric. • These st a tements a re termin a ted with a semi-colon. • The control line for the "for" loop cont a in two semi-colons but a ccounts for only one semi colon. 14
13. Example 15
14. Test Yourselves
22. Software Metrics Complexity
23. Function Metrics • Cyclomatic Complexity. It is a quantitative measure of the number of linearly independent paths. • P a ths occur when "while,” "for,” "if,” "c a se," a nd "goto" keywords a ppe a r within the function. • If the source code cont a ined no control f low st a tements (condition a ls or decision points), the complexity would be 1 • If the code h a d one single-condition IF st a tement, there would be two p a ths through the code: one where the IF st a tement ev a lu a tes to TRUE a nd a nother one where it considers to be FALSE. • Two nested single-condition IFs, or one block with two conditions, would produce a complexity of 3. 25
24. Cyclomatic Complexity 26 CC = Edge - Node + 2 Or CC = ConditionalNodes + 1
25. Cyclomatic Complexity 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 27
26. 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 28
34. Structural Metrics Abstractness Instability
35. Is this a good design? 37
36. Abstractness • It is the degree to which a cl a ss or p a ck a ge emph a sizes a bstr a ction over concrete implement a tion • It is a v a lue 0 to 1: • For p a ck a ges, It is the r a tio of a bstr a ct cl a sses or interf a ces to the tot a l number of cl a sses within a p a ck a ge. • For cl a sses, It is 0 for a concrete cl a ss a nd 1 for a n interf a ce or a bstr a ct cl a sses 38
37. Instability • Indic a tes whether: ( a ) the item is m a inly used by others (st a ble – h a rd to ch a nge); or (b) it m a inly depends on other items (in-st a ble – ch a nge a ble). • It is a v a lue between 0 a nd 1: • 0 only incoming dependencies to • 1 (only outgoing dependencies). 39
38. Distance • Dist a nce: how f a r a p a ck a ge is a w a y from the M a in Sequence • D = A + I – 1 • V a lues -1 to 1 • Absolute Dist a nce |D| 40
39. Distance 41 Abstract Concrete Stable Hard to Change Only incoming dependencies Unstable Changeable Only outgoing dependencies the main sequence Painful Useless 0 1 1 0 Instability Abstractness
40. Is this a good design? 42
41. project3.common.model project3.client.UI project3.server.controller
43. Questions 45
44. Lab
45. Reminder 47 Calculate the structural metrics for classes here:
46. CSC 307 Introduction to Software Engineering Javier Gonzalez-Sanchez, Ph.D. javiergs@calpoly.edu Summer 2024 Copyright. These slides can only be used as study material for the class CSC307 at Cal Poly. They cannot be distributed or used for another purpose.