See related: https://guava.dev/releases/23.0/api/docs/com/google/common/collect/Maps.html#newHashMapWithExpectedSize-int-
On Tue, May 5, 2020 at 11:03 AM <naoto.s...@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.s...@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.s...@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 >
