Mining Maximal High-Utility Itemsets from a transaction database with utility information using the CHUI-Miner(Max) Algorithm (SPMF documentation)
This example explains how to run the CHUI-Miner(Max) algorithm using the SPMF open-source data mining library.
How to run this example?
- If you are using the graphical interface, (1) choose the "CHUI-Miner(Max)" algorithm, (2) select the input file "DB_utility.txt", (3) set the output file name (e.g. "output.txt") (4) set the minimum utility to 25 and (5) click "Run algorithm".
- If you want to execute this example from the command line,
then execute this command:
java -jar spmf.jar run CHUI-MinerMax DB_utility.txt output.txt 25 in a folder containing spmf.jar and the example input file DB_utility.txt. - If you are using the source code version of SPMF, launch the file "MainTestCHUIMinerMax_saveToFile.java" in the package ca.pfv.SPMF.tests.
What is CHUI-Miner?
CHUI-Miner(Max) (Wu et al., 2019) is an algorithm for discovering maximal high-utility itemsets in a transaction database containing utility information.
There has been many work on the topic of high-utility itemset mining. A limitation of many high-utility itemset mining algorithms is that they generate too much itemsets as output. The CHUI-Miner(Max) algorithm was designed to discover only the high-utility itemsets that are maximal. A maximal high utility itemset is an itemset that is not included in any other high utility itemsets.
What is the input?
CHUI-Miner(Max) takes as input a transaction database with utility information and a minimum utility threshold min_utility (a positive integer). Let's consider the following database consisting of 5 transactions (t1,t2...t5) and 7 items (1, 2, 3, 4, 5, 6, 7). This database is provided in the text file "DB_utility.txt" in the package ca.pfv.spmf.tests of the SPMF distribution.
| Items | Transaction utility | Item utilities for this transaction | |
| t1 | 3 5 1 2 4 6 | 30 | 1 3 5 10 6 5 |
| t2 | 3 5 2 4 | 20 | 3 3 8 6 |
| t3 | 3 1 4 | 8 | 1 5 2 |
| t4 | 3 5 1 7 | 27 | 6 6 10 5 |
| t5 | 3 5 2 7 | 11 | 2 3 4 2 |
Each line of the database is:
- a set of items (the first column of the table),
- the sum of the utilities (e.g. profit) of these items in this transaction (the second column of the table),
- the utility of each item for this transaction (e.g. profit generated by this item for this transaction)(the third column of the table).
Note that the value in the second column for each line is the sum of the values in the third column.
What are real-life examples of such a database? There are several applications in real life. One application is a customer transaction database. Imagine that each transaction represents the items purchased by a customer. The first customer named "t1" bought items 3, 5, 1, 2, 4 and 6. The amount of money spent for each item is respectively 1 $, 3 $, 5 $, 10 $, 6 $ and 5 $. The total amount of money spent in this transaction is 1 + 3 + 5 + 10 + 6 + 5 = 30 $.
What is the output?
The output of CHUI-Miner(Max) is the set of maximal high utility itemsets having a utility no less than a min_utility threshold (a positive integer) set by the user. To explain what is a maximal high utility itemset, it is necessary to review some definitions.
An itemset is an unordered set of distinct items. The utility of an itemset in a transaction is the sum of the utility of its items in the transaction. For example, the utility of the itemset {1 4} in transaction t1 is 5 + 6 = 11 and the utility of {1 4} in transaction t3 is 5 + 2 = 7. The utility of an itemset in a database is the sum of its utility in all transactions where it appears. For example, the utility of {1 4} in the database is the utility of {1 4} in t1 plus the utility of {1 4} in t3, for a total of 11 + 7 = 18. A high utility itemset is an itemset such that its utility is no less than min_utility.
A maximal high utility itemset (CHUI) is a high-utility itemset that not included in any other high utility itemset.
For example, if we run CHUI-Miner(Max) with a minimum utility of 25 we obtain 2 maximal high-utility itemsets:
| itemsets | utility |
| {1, 2, 3, 4, 5, 6} | 30 |
| {1, 3, 5, 7} | 27 |
If the database is a transaction database from a store, we could interpret these results as all the largest groups of items bought together that generated a profit of 25 $ or more.
Input file format
The input file format of CHUI-Miner(Max) is defined as follows. It is a text file. Each lines represents a transaction. Each line is composed of three sections, as follows.
- First, the items contained in the transaction are listed. An item is represented by a positive integer. Each item is separated from the next item by a single space. It is assumed that all items within a same transaction (line) are sorted according to a total order (e.g. ascending order) and that no item can appear twice within the same transaction.
- Second, the symbol ":" appears and is followed by the transaction utility (an integer).
- Third, the symbol ":" appears and is followed by the utility of each item in this transaction (an integer), separated by single spaces.
For example, for the previous example, the input file is defined as follows:
3 5 1 2 4 6:30:1 3 5 10 6 5
3 5 2 4:20:3 3 8 6
3 1 4:8:1 5 2
3 5 1 7:27:6 6 10 5
3 5 2 7:11:2 3 4 2
Consider the first line. It means that the transaction {3, 5, 1, 2, 4, 6} has a total utility of 30 and that items 3, 5, 1, 2, 4 and 6 respectively have a utility of 1, 3, 5, 10, 6 and 5 in this transaction. The following lines follow the same format.
Output file format
The output file format of CHUI-Miner(Max) is defined as follows. It is a text file, where each line represents a maximal high utility itemset. On each line, the items of the itemset are first listed. Each item is represented by an integer, followed by a single space. After, all the items, the keyword "#SUP:" appears and is followed by the support of the itemset. The support of an itemset is how many times the itemset appeared in the database. Then, the keyword #UTIL: " appears and is followed by the utility of the itemset. For example, we show below the output file for this example.
6 4 2 1 5 3 #SUP: 1 #UTIL: 30
7 5 3 1 #SUP: 1 #UTIL: 27
For example, the second line indicates that the itemset {1, 3, 5, 7} has a support of 1 transaction and a utility of 27$. The other lines follows the same format.
Performance
High utility itemset mining is a more difficult problem than frequent itemset mining. Therefore, high-utility itemset mining algorithms are generally slower than frequent itemset mining algorithms. The CHUI-Miner(Max) algorithm was proposed in 2019 to discover only the high-utility itemsets that are maximal. It is generally faster to discover maximal high utility itemsets than discovering all high-utility itemsets.
Note that there exists another variation of this algorithm named CHUI-Miner or CHUI-Miner(Closed) for discovering the closed high-utility itemsets. It is also included in SPMF.
Implementation details
This is an implementation of CHUI-Miner(Max), implemented by P. Fournier-Viger. This is an alternative implementation that was not used in the paper. The main differences with the implementation in the paper is that this implementation (1) does not calculate utility-unit arrays (see the paper) and (2) adds the EUCP optimizations introduced in the FHM algorithm.
In the source code version of SPMF, there are two examples of using CHUI-Miner(Max) in the package ca.pfv.spmf.tests. The first one is MainTestCHUIMinerMax_saveToFile, which saves the result to an output file. The second one is MainTestCHUIMinerMax_saveToMemory, which saves the result to memory.
Where can I get more information about the CHUI-Miner(Max) algorithm?
This is the reference of the article describing the CHUI-Miner(Max) algorithm:
Wu. C.-W., Fournier-Viger, P., Gu, J. Y., Tseng, V.S. (2019). Mining Compact High Utility Itemsets without Candidate Generation . In: Fournier-Viger et al. (eds). High-Utility Pattern Mining: Theory, Algorithms and Applications, Springer.
Besides, for a general overview of high utility itemset mining, you may read this survey paper.