Clever Geek Handbook

Add atomic twins

There is a note at the end of the brief description of the atomization package:

... You can also navigate floats

using the transformations Float.floatToIntBits

and Float.intBitstoFloat

and doubles

using the transformations Double.doubleToLongBits

and Double.longBitsToDouble

.

Obviously, you cannot just add these values ​​together in a way that is equivalent to atomic addAndGet

for the value double

.

private AtomicLong sum = new AtomicLong();
...
// This would almost certainly NOT work.
public long add(double n) {
  return sum.addAndGet(Double.doubleToLongBits(n));
}

It can be assumed that I am trying very hard NOT to use synchronized

.

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Guava provides AtomicDouble

, and using this is probably the easiest thing to do, not rolling it yourself ...

However, it is internally implemented with a wrapper around it AtomicLong

, you can see their implementation addAndGet

here ; it's mostly

while (true) {
  long current = value;
  double currentVal = longBitsToDouble(current);
  double nextVal = currentVal + delta;
  long next = doubleToRawLongBits(nextVal);
  if (updater.compareAndSet(this, current, next)) {
    return nextVal;
  }
}


which is really the only way to do it without having to deal with the assembly.

Full disclosure: I'm working on Guava.

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