<i18n dev>  RFR: 8244152: Remove unnecessary hash map resize in LocaleProviderAdapters
peter.levart at gmail.com
Tue May 5 16:37:55 UTC 2020
On 4/30/20 12:18 AM, naoto.sato at oracle.com wrote:
> Please review this small fix to the following issue:
> The proposed changeset is located at:
> 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
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