RFR 8017540: Improve multi-threaded contention behavior of BigInteger.toString() radix conversion cache

[Aleksey Shipilev]

On 06/27/2013 10:37 AM, Peter Levart wrote:
> Hi,
> 
> This version seems correct. Maybe just replace double volatile read at
> length re-check with a single one:
> 
> 
>     private static BigInteger getRadixConversionCache(int radix, int
> exponent) {
>         BigInteger[] cacheLine = powerCache[radix]; // volatile read
>         if (exponent < cacheLine.length)
>             return cacheLine[exponent];
> 
>         int oldLength = cacheLine.length;
>         cacheLine = Arrays.copyOf(cacheLine, exponent + 1);
>         for (int i = oldLength; i <= exponent; i++)
>             cacheLine[i] = cacheLine[i - 1].pow(2);
> 
>         BigInteger[][] pc = powerCache; // volatile read again
>         if (exponent >= pc[radix].length) {
>             pc = pc.clone();
>             pc[radix] = cacheLine;
>             powerCache = pc; // volatile write, publish
>         }
>         return cacheLine[exponent];
>     }
> 

Yes, I'm voting for this one. All other improvements Peter had
suggested, while interesting, seem to not to worth the trouble.

-Aleksey.