performance / understanding question about fastutil HOT 4 CLOSED

On Thu, Aug 24, 2023, 11:15 AM David Urbansky ***@***.***> wrote: I am stuck by not understanding some performance metrics I'm obtaining. I found that iterating through an IntOpenHashSet AND adding into another IntOpenHashSet takes much longer than expected. When I just iterate, it takes 13ms, when I just add it takes 160ms but when I do both it takes not 160+13 but 2800 (17x longer than expected). Can you point me in the direction to understand this behavior? Please be aware that I know in this example I could do addAll or use an initial capacity to dramatically boost the speed but I boiled it down to those basics that I don't understand. This is the test code: IntOpenHashSet integers = new IntOpenHashSet(); long ms = System.currentTimeMillis(); for (int i = 0; i < 3_000_000; i++) { integers.add(i); } System.out.println(System.currentTimeMillis() - ms + "ms adding 3M integers to IntOpenHashSet"); ms = System.currentTimeMillis(); for (Integer integer : integers) { integer++; } System.out.println(System.currentTimeMillis() - ms + "ms iterating through IntOpenHashSet"); IntOpenHashSet anotherHashSet = new IntOpenHashSet(); ms = System.currentTimeMillis(); for (int integer : integers) { anotherHashSet.add(integer); } System.out.println(System.currentTimeMillis() - ms + "ms iterating AND adding to IntOpenHashSet"); outputs 160ms adding 3M integers to IntOpenHashSet 13ms iterating through hashset 2809ms iterating AND adding to IntOpenHashSet — Reply to this email directly, view it on GitHub <#303>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AA6GRS23BL5PBVZWDTMLCJLXW5VYNANCNFSM6AAAAAA35GAVFE> . You are receiving this because you are subscribed to this thread.Message ID: ***@***.***>