[GROOVY-10964] List.minus() slow for Numbers

• Type: Improvement
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 2.4.0, 3.0.9, 4.0.9
• Fix Version/s: 5.0.0-alpha-1
• Component/s: groovy-jdk
• Labels: Collections Groovy List Number breaking
• Flags: Patch
• External issue URL: https://stackoverflow.com/questions/75638273/why-is-the-groovy-method-minus-so-slow-with-lists-of-numbers

Language

groovy

• Assignee: Paul King
• Reporter: Ingo Wilms
• Created: 07/Mar/23 02:15
• Updated: 23/Aug/23 09:11
• Resolved: 31/Jul/23 03:59

Description

In List.minus() is a n*LOG(n) version for comparable objects. Only for numbers, there is a dedicated slower n^2*LOG(n) version. Is there a reason for this? It exists since 2.4.0 and hasn't changed much since then. Here is part of the code from version 4.0.9:

 

// if (nlgnSort && (head instanceof Comparable)) {
    //n*LOG(n) version
    Set<T> answer;
    if (head instanceof Number) {
        answer = new TreeSet<>(comparator);
        answer.addAll(self1);
        for (T t : self1) {
            if (t instanceof Number) {
                for (Object t2 : removeMe1) {
                    if (t2 instanceof Number) {
                        if (comparator.compare(t, (T) t2) == 0)
                            answer.remove(t);
                    }
                }
            } else {
                if (removeMe1.contains(t))
                    answer.remove(t);
            }
        }
    } else {
        answer = new TreeSet<>(comparator);
        answer.addAll(self1);
        answer.removeAll(removeMe1);
    }

    for (T o : self1) {
        if (answer.contains(o))
            ansCollection.add(o);
    }
} else {
    //n*n version 

I fail to see why the whole extra block for numbers beginning with

if (head instanceof Number) { 

is necessary.

 

Issue Links

• links to: GitHub Pull Request #1875