<i18n dev> [15] RFR: 8244459: Optimize the hash map size in LocaleProviderAdapters

[Joe Wang]

On 5/5/2020 2:08 PM, naoto.sato at oracle.com wrote:
> Thanks, all. I didn't see this coming!

+1, just when one might think it was just a minor tweak... ;-)

>
> If I understand the discussion correctly, Peter's suggestion is the 
> most optimal (Mark, your formula produces 1 for the expected size is 
> 0, although it won't be happening in this particular case). And Joe, 
> thank you for finding my silly mistake :-) So here is the updated webrev:
>
> http://cr.openjdk.java.net/~naoto/8244459/webrev.01/

+1

-Joe

>
> Naoto
>
>
> On 5/5/20 11:01 AM, naoto.sato at oracle.com wrote:
>> And here is the fix. Please review.
>>
>> http://cr.openjdk.java.net/~naoto/8244459/webrev.00/
>>
>> Naoto
>>
>> On 5/5/20 10:25 AM, naoto.sato at oracle.com wrote:
>>> Hi Peter,
>>>
>>> You are correct. Thanks. I'll remove that initial value of 16.
>>>
>>> Naoto
>>>
>>> On 5/5/20 9:37 AM, Peter Levart wrote:
>>>> Hi Naoto,
>>>>
>>>> On 4/30/20 12:18 AM, naoto.sato at oracle.com wrote:
>>>>> Hello,
>>>>>
>>>>> Please review this small fix to the following issue:
>>>>>
>>>>> https://bugs.openjdk.java.net/browse/JDK-8244152
>>>>>
>>>>> The proposed changeset is located at:
>>>>>
>>>>> https://cr.openjdk.java.net/~naoto/8244152/webrev.00/
>>>>>
>>>>> The hash map used there didn't have initial capacity, even though 
>>>>> the exact numbers are known.
>>>>
>>>>
>>>> Well, it has to be calculated 1st (countTokens), but I guess this 
>>>> pays off when HashSet (the backing HashMap) does not have to be 
>>>> rehashed then.
>>>>
>>>> The expression you use:
>>>>
>>>>      Math.max((int)(tokens.countTokens() / 0.75f) + 1, 16)
>>>>
>>>> ...has a minimum value of 16. Why is that? 16 is just HashMap's 
>>>> default initialCapacity if not specified explicitly. But if you 
>>>> only want to store say 1 entry in the map, you can specify 2 as 
>>>> initialCapacity and HashMap will happily work for such case without 
>>>> resizing.
>>>>
>>>>
>>>> So you could just use:
>>>>
>>>>      (int)(tokens.countTokens() / 0.75f) + 1
>>>>
>>>> And even this expression is sometimes overshooting the minimal 
>>>> required value by 1 (when # of tokens is "exact" multiple of 0.75f, 
>>>> say 6). I think the following could be used to optimally pre-size 
>>>> the HashMap with default load factor 0.75:
>>>>
>>>>      (tokens.countTokens() * 4 + 2) / 3
>>>>
>>>>
>>>> Regards, Peter
>>>>
>>>>>
>>>>> Naoto