Hello, Prof. Philippe Fournier-Viger.

Have you read paper "Mining top-k high utility itemsets with effective threshold raising strategies" from Krishnamoorthy (2019)?

In section 4.2.2 , Why is the maximum number of breakpoints considered 3 (q=3 , contiguous)?

If we have more breakpoints in one itemset, what should we do?

It is a heuristic and you can certainly use higher values of q. There is also downside to using higher values of q as mentioned in section 4.2.2 (below definition 18) of the paper. Please also refer to the example given in Figure 3, where the utilities of subsets are estimated using fdaec and daec. One can observe that utility estimate of fac is 15 (actual 57), estimate of fc is -30 (actual 22). As you remove more items, the estimate is likely to fall dramatically. Essentially, this might lead to wasted computation. One can also set a dynamically threshold (not considered in the paper) and stop generation of subsets when the estimate becomes zero or negative.

Hope this clarifies.

Thank you. Thank you. This issue is clarifies now.