Am 24.09.2014 um 22:25 schrieb Peter Levart:
Hi,
String.hashCode() caches the result, so repeatable call to same String instance is faster for 2nd
and further invocations. But the computation of hash code itself could be accelerated for a factor
of 2 or more on todays CPUs. How? By parallelizing it. And I don't mean computing it in multiple
threads.
Here is a surprising result of a simple benchmark which computes hash code of a 128 character
string in 6 different ways:
Benchmark Mode Samples Score Score error Units
j.t.HashBench.hashCode thrpt 8 8420103.795 162447.069 ops/s
j.t.HashBench.hashCode0 thrpt 8 8439058.660 2842.755 ops/s
j.t.HashBench.hashCode1 thrpt 8 13809510.573 337888.132 ops/s
j.t.HashBench.hashCode2 thrpt 8 15543687.568 716152.160 ops/s
j.t.HashBench.hashCode3 thrpt 8 18173224.431 49410.256 ops/s
j.t.HashBench.hashCode3x thrpt 8 8543020.232 18158.686 ops/s
Source:
http://cr.openjdk.java.net/~plevart/misc/StringHash/HashBench.java
This is really great!
Couldn't this be a tweak via HotSpot, instead uglifying and bloating the Java
and hence the byte code?
-Ulf
