Checking if an Integer is an Exact Binary Power

[Andrei Alexandrescu via Digitalmars-d]

On 4/23/16 9:06 AM, Vladimir Panteleev wrote:
> On Saturday, 23 April 2016 at 13:04:00 UTC, Nordlöw wrote:
>> Wanted: CT-trait and run-time predicate for checking whether its
>> single integer parameter is an exact power of two.
>
> popcnt(x) <= 1 ?

Would be interesting to see how it compares to the handwritten version 
on different machines. popcnt has a reputation of being slow in older 
CPUs, in recent ones it has a latency of 3 cycles and a throughput of 1 
cycle. -- Andrei