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.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/%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
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