Did you mark the class and fields all as final? That might help the compiler realize it could in-line stuff and avoid the constructor (not likely, but possible)
On Sun, Apr 14, 2013 at 4:52 PM, Robin Anil <[email protected]> wrote: > With a new immutable Element in the iterator, the iteration behavior is > corrected but. There is a performance degradation of about 10% and > nullifies what I have done with the patch. > > See > > https://docs.google.com/spreadsheet/ccc?key=0AhewTD_ZgznddGFQbWJCQTZXSnFULUYzdURfWDRJQlE#gid=1 > > Robin Anil | Software Engineer | +1 312 869 2602 | Google Inc. > > > On Sun, Apr 14, 2013 at 11:28 AM, Ted Dunning <[email protected]> > wrote: > > > Yeah... but we still have to fix the iterator. > > > > > > On Sun, Apr 14, 2013 at 8:58 AM, Robin Anil <[email protected]> > wrote: > > > > > Here is an iteration style that works as is with today's behaviour of > > > hasNext > > > > > > 1. > > > 2. Element thisElement = null; > > > 3. Element thatElement = null; > > > 4. boolean advanceThis = true; > > > 5. boolean advanceThat = true; > > > 6. > > > 7. Iterator<Element> thisNonZero = this.iterateNonZero(); > > > 8. Iterator<Element> thatNonZero = x.iterateNonZero(); > > > 9. > > > 10. double result = 0.0; > > > 11. while (true) { > > > 12. *if (advanceThis) { > > > * > > > 13. * if (!thisNonZero.hasNext()) { > > > * > > > 14. * break; > > > * > > > 15. * } > > > * > > > 16. * thisElement = thisNonZero.next(); > > > * > > > 17. * } > > > * > > > 18. * if (advanceThat) { > > > * > > > 19. * if (!thatNonZero.hasNext()) { > > > * > > > 20. * break; > > > * > > > 21. * } > > > * > > > 22. * thatElement = thatNonZero.next(); > > > * > > > 23. * }* > > > 24. if (thisElement.index() == thatElement.index()) { > > > 25. > > > 26. result += thisElement.get() * thatElement.get(); > > > 27. advanceThis = true; > > > 28. advanceThat = true; > > > 29. } else if (thisElement.index() < thatElement.index()) { > > > 30. advanceThis = true; > > > 31. advanceThat = false; > > > 32. } else { > > > 33. advanceThis = false; > > > 34. advanceThat = true; > > > 35. } > > > 36. } > > > > > > > > > On Sat, Apr 13, 2013 at 1:47 AM, Ted Dunning <[email protected]> > > > wrote: > > > > > > > The caller is not at fault here. The problem is that hasNext is > > > advancing > > > > the iterator due to a side effect. The side effect is impossible to > > > avoid > > > > at the level of the caller. > > > > > > > > Sent from my iPhone > > > > > > > > On Apr 12, 2013, at 12:22, Sean Owen <[email protected]> wrote: > > > > > > > > > I'm sure I did (at least much of) the AbstractIterator change so > > blame > > > > > me... but I think the pattern itself is just fine. It's used in > many > > > > > places in the project. Reusing the value object is a big win in > some > > > > > places. Allocating objects is fast but a trillion of them still > adds > > > > > up. > > > > > > > > > > It does contain a requirement, and that is that the caller is > > supposed > > > > > to copy/clone the value if it will be used at all after the next > > > > > iterator operation. That's the 0th option, to just fix the caller > > > > > here. > > > > > > > > > > On Fri, Apr 12, 2013 at 7:49 PM, Ted Dunning < > [email protected]> > > > > wrote: > > > > >> The contract of computeNext is that there are no side effects > > visible > > > > >> outside (i.e. apparent functional style). This is required since > > > > >> computeNext is called from hasNext(). > > > > >> > > > > >> We are using a side-effecting style so we have a bug. > > > > >> > > > > >> We have two choices: > > > > >> > > > > >> a) use functional style. This will *require* that we allocate a > new > > > > >> container element on every call to computeNext. This is best for > > the > > > > user > > > > >> because they will have fewer surprising bugs due to reuse. If > > > > allocation > > > > >> is actually as bad as some people think (I remain skeptical of > that > > > > without > > > > >> tests) then this is a bad move. If allocation of totally > ephemeral > > > > objects > > > > >> is as cheap as I think, then this would be a good move. > > > > >> > > > > >> b) stop using AbstractIterator and continue with the re-use style. > > > And > > > > add > > > > >> a comment to prevent a bright spark from reverting this change. > (I > > > > suspect > > > > >> that the bright spark who did this in the first place was me so I > > can > > > be > > > > >> rude) > > > > > > > > > >
