Can we see the implementation of your benchmark? Accurate benchmarking is extremely nontrivial.
On Tue, Apr 2, 2013 at 2:34 PM, Ivan Gerasimov <ivan.gerasi...@oracle.com>wrote: > Thank you Stanimir! > > My main goal was to get rid of early and possibly unneeded memory > allocation. > I thought that System.arraycopy() would somehow compensate the need to > traverse the array twice. > However testing shows that my code works a bit faster at least when > dealing with Integer arrays of size from 1 to 100. > > Sincerely, > Ivan > > On 02.04.2013 23:25, Stanimir Simeonoff wrote: > >> The current version is cache oblivious. In any case for smaller arrays >> (like COW) System.arrayCopy won't yield any noticeable difference. >> Also, iirc System.arrayCopy places a memory barrier which in the COW case >> is unneeded. >> >> Stanimir >> >> >> >> On Tue, Apr 2, 2013 at 9:53 PM, Ivan Gerasimov >> <ivan.gerasi...@oracle.com<mailto: >> ivan.gerasimov@oracle.**com <ivan.gerasi...@oracle.com>>> wrote: >> >> Hello everybody! >> >> Please review my proposal for the >> CopyOnWriteArrayList.**addIfAbsent() method optimization. >> >> http://washi.ru.oracle.com/~**igerasim/webrevs/8011215/** >> webrev/index.html<http://washi.ru.oracle.com/~igerasim/webrevs/8011215/webrev/index.html> >> <http://washi.ru.oracle.com/%**7Eigerasim/webrevs/8011215/** >> webrev/index.html<http://washi.ru.oracle.com/%7Eigerasim/webrevs/8011215/webrev/index.html> >> > >> >> >> Here is the original function body: >> ------------------------------**------------------ >> Object[] elements = getArray(); >> int len = elements.length; >> Object[] newElements = new Object[len + 1]; <-- allocate new >> array in advance >> for (int i = 0; i < len; ++i) { >> if (eq(e, elements[i])) <-- check whether >> e is null on every iteration >> return false; // exit, throwing away copy >> else >> newElements[i] = elements[i]; <-- copy elements >> one by one >> } >> newElements[len] = e; >> setArray(newElements); >> ------------------------------**------------------ >> The proposed change is to reuse CopyOnWriteArrayList.indexOf() >> function to check if e is already in the array. >> If the check passed, new array is allocated withArrays.copyOf(). >> It uses native System.arraycopy(), which is probably faster than >> copying elements in the loop. >> >> Sincerely yours, >> Ivan >> >> ______________________________**_________________ >> Concurrency-interest mailing list >> Concurrency-interest@cs.**oswego.edu<concurrency-inter...@cs.oswego.edu> >> >> <mailto:Concurrency-interest@**cs.oswego.edu<concurrency-inter...@cs.oswego.edu> >> > >> >> http://cs.oswego.edu/mailman/**listinfo/concurrency-interest<http://cs.oswego.edu/mailman/listinfo/concurrency-interest> >> >> >> > -- Louis Wasserman
