> We could check for the existing cacheLine.length right before installing
the new one
Do you mean something like this ?
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 + 1; i++)
cacheLine[i] = cacheLine[i - 1].square();
if (exponent >= powerCache[radix].length) { // volatile read again
BigInteger[][] pc = Arrays.copyOf(powerCache);
pc[radix] = cacheLine;
powerCache = pc; // volatile write, publish
}
return cacheLine[exponent];
}
On Wed, Jun 26, 2013 at 10:31 AM, Aleksey Shipilev <
aleksey.shipi...@oracle.com> wrote:
> On 26.06.2013, at 7:31, Dmitry Nadezhin <dmitry.nadez...@gmail.com> wrote:
>
> > We have two versions after private discussion with Aleksey.
> >
> > BigInteger getRadixConversionCache(int radix, int exponent) {
> > BigInteger[][] pc = powerCache; // volatile read
> > BigInteger[] cacheLine = pc[radix];
> > if (exponent < cacheLine.length)
> > return cacheLine[exponent];
> >
> > int oldSize = cacheLine.length;
> > cacheLine = Arrays.copyOf(cacheLine, exponent + 1);
> > for (int i = oldSize; i < exponent + 1; i++)
> > cacheLine[i] = cacheLine[i - 1].square();
> >
> > pc = Arrays.copyOf(powerCache);
> > pc[radix] = cacheLine;
> > powerCache = pc; // volatile write, publish
> > return cacheLine[exponent];
> > }
>
> Thanks, I like this version a lot better. We could check for the existing
> cacheLine.length right before installing the new one, so the opportunity to
> overwrite larger cacheLine would be minimal, but I do think the probability
> of unlucky timing is very low, and the argument is moot :) Let's keep it
> simple.
>
> -Aleksey.
