Detecting plagiarism in computer source code
View Patent ↗Plagiarism of software source code is a serious problem in two distinct areas of endeavor—cheating by students at schools and intellectual property theft at corporations. A number of algorithms have been implemented to check source code files for plagiarism, each with their strengths and weaknesses. This invention detects plagiarism by comparing statements within source code of a first program to comments within source code of a second program.
1. A computer-implemented method comprising:
creating, by a computer system, a first array of lines of functional program code from a first program source code file, the first program source code file including the lines of functional program code of a first program written in a first programming language and lines of non-functional comments of the first program;
creating, by the computer system, a second array of lines of non-functional comments from a second program source code file, the second program source code file including lines of functional program code of a second program written in a second programming language and the lines of non-functional comments of the second program, wherein the first programming language is different from the second programming language, and wherein the second array of non-functional comments is created using a predefined list of programming language specific special characters to determine the beginning and end of comments in the second program source code file;
comparing, by the computer system, the lines of functional program code from the first array with the lines of non-functional comments from the second array to find similar lines;
calculating, by the computer system, a similarity number based on the similar lines, wherein calculating the similarity number comprises finding a number of matching functional statements in the first array and non-functional comments in the second array indicating that the non-functional comments of the second program source code file contain functional program code of the first program source code file; and
presenting to a user an indication of copying of the first program source code file wherein said indication of copying is defined by the similarity number.
2. The method of claim 1 ) wherein:
calculating a similarity number comprises finding a number of matching lines in the first and second arrays weighted by the number of characters in the lines.
3. The method of claim 1 ) wherein:
calculating a similarity number comprises finding a number of lines in the first and second arrays that have an edit distance less than a given threshold.
4. A computer-readable storage medium storing executable instructions to cause a computer system to perform a method comprising:
creating a first array of lines of functional program code from a first program source code file, the first program source code file including the lines of functional program code of a first program written in a first programming language and lines of non-functional comments of the first program;
creating a second array of lines of non-functional comments from a second program source code file, the second program source code file including lines of functional program code of a second program written in a second programming language and the lines of non-functional comments of the second program, wherein the first programming language is different from the second programming language, and wherein the second array of non-functional comments is created using a predefined list of programming language specific special characters to determine the beginning and end of comments in the second program source code file;
comparing the lines of functional program code from the first array with the lines of non-functional comments from the second array to find similar lines;
calculating a similarity number based on the similar lines, wherein calculating the similarity number comprises finding a number of matching functional statements in the first array and non-functional comments in the second array indicating that the non-functional comments of the second program source code file contain functional program code of the first program source code file; and
presenting to a user an indication of copying of the first program source code file wherein said indication of copying is defined by the similarity number.
5. The computer-readable storage medium of claim 4 ) wherein:
calculating a similarity number comprises finding a number of matching lines in the first and second arrays weighted by the number of characters in the lines.
6. The computer-readable storage medium of claim 4 ) wherein:
calculating a similarity number comprises finding a number of lines in the first and second arrays that have an edit distance less than a given threshold.
7. A computer-implemented apparatus comprising:
a computer; and
a source code matching program on the computer, the source code matching program comprising:
means for creating a first array of lines of functional program code from a first program source code file, the first program source code file including the lines of functional program code of a first program written in a first programming language and lines of non-functional comments of the first program;
means for creating a second array of lines of non-functional comments from a second program source code file, the second program source code file including lines of functional program code of a second program written in a second programming language and the lines of non-functional comments of the second program, and wherein the second array of non-functional comments is created using a predefined list of programming language specific special characters to determine the beginning and end of comments in the second program source code file;
means for comparing the lines of functional program code from the first array with the lines of non-functional comments from the second array to find similar lines;
means for calculating a similarity number based on the similar lines, wherein calculating the similarity number comprises finding a number of matching functional statements in the first array and non-functional comments in the second array indicating that the non-functional comments of the second program source code file contain functional program code of the first program source code file; and
means for presenting to a user an indication of copying of the first program source code file wherein said indication of copying is defined by the similarity number.
8. The apparatus of claim 7 ) wherein:
the means for calculating a similarity number comprises means for finding a number of matching lines in the first and second arrays weighted by the number of characters in the lines.
9. The apparatus of claim 7 ) wherein:
the means for calculating a similarity number comprises finding a number of lines in the first and second arrays that have an edit distance less than a given threshold.