RFR: [6904367]: (coll) IdentityHashMap is resized before exceeding the expected maximum size

[Martin Buchholz]

I'd like to offer an alternative version of this change.  webrev coming
soon.


On Sun, Jul 6, 2014 at 8:12 AM, Ivan Gerasimov <ivan.gerasimov at oracle.com>
wrote:

> Thanks for suggestion Jeff!
>
> I've tried it, but it doesn't seem to make a difference on my machine.
> Here are the numbers. I measured the time of a single put in nanoseconds.
>
>
> ----------- | vanila | fix1  | fix2
> client      | 8292   | 8220  | 8304
> server      | 8197   | 8198  | 8221
> interpreter | 13980  | 14478 | 14152
>
>
> fix1 - the fix from webrev #3
> fix2 - the fix with your suggestion
>
> Sincerely yours,
> Ivan
>
>
>
> On 06.07.2014 15:13, Jeff Hain wrote:
>
>>
>>
>> >So, I reverted this change to the original code, but added a single
>> >check of the current table size before doing any modifications to the
>> map.
>> >This is to address the issue #4, and this doesn't seem to introduce any
>> >significant penalty.
>> >
>> >Would you please help review the updated webrev:
>> >
>> >http://cr.openjdk.java.net/~igerasim/6904367/3/webrev/ <
>> http://cr.openjdk.java.net/%7Eigerasim/6904367/3/webrev/>
>>
>> >
>> >Sincerely yours,
>> >
>> >Ivan
>>
>> It's possible to avoid the capacity test for the general case:
>> put {
>>     ...while loop...
>>
>>     if (size < threshold) {
>>         modCount++;
>>         tab[i] = k;
>>         tab[i + 1] = value;
>>         ++size;
>>     } else {
>>         putAndResize(k, value, i);
>>     }
>>     return null;
>> }
>> private void putAndResize(Object k, Object value, int i) {
>>     if (size == MAXIMUM_CAPACITY - 1)
>>         throw new IllegalStateException("Capacity exhausted.");
>>     modCount++;
>>     Object[] tab = table;
>>     tab[i] = k;
>>     tab[i + 1] = value;
>>     ++size;
>>     resize(tab.length); // len == 2 * current capacity.
>> }
>>
>> It seems faster more often than not, but it adds more (and copied) code:
>> not sure it's worth it.
>>
>> -Jeff
>>
>>
>>
>