Processor support for select operations

Paul Elschot paul.j.elschot at
Wed Nov 12 19:09:29 UTC 2014

The difference in performance between Java and C for bit selection from
a long is already quite small, so I'll wait for the optimization on
power-of-two indexing and avoid Unsafe.

Paul Elschot

On 11-11-14 20:00, Vitaly Davidovich wrote:
> But in the meantime, just trying Unsafe to see what the perf benefit
> would be is still interesting, no?
> Sent from my phone
> On Nov 11, 2014 1:54 PM, "John Rose" <john.r.rose at
> <mailto:john.r.rose at>> wrote:
>     On Nov 11, 2014, at 10:16 AM, Paul Elschot <paul.j.elschot at
>     <mailto:paul.j.elschot at>> wrote:
>>     A little masking might be enough to enforce the ranges, see the
>>     code in
>>     my other reply.
>     Power-of-two array indexing is an important use case which can be
>     optimized without resorting to Unsafe.
>     We're working on it. 
>     See
>     — John

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