On Mon, Sep 12, 2011 at 8:54 PM, Eric Niebler <eric@boostpro.com> wrote:
On 9/12/2011 4:06 AM, Thomas Heller wrote:
On Monday, September 12, 2011 02:57:21 PM Joel de Guzman wrote:
For example, here is the current CT status of Phoenix2 vs Phoenix3 comparing the elapsed (CT) time for the phoenix2 vs. phoenix3 lambda_tests.cpp (**):
MSVC 10: Phoenix2: 00:04.5 Phoenix3: 00:29.9
G++ 4.5: Phoenix2: 00:02.6 Phoenix3: 00:04.7
I wasn't aware that Phoenix3 was so bad under MSVC 10.
Me neither. If that's the case, we have work to do.
You all know that Phoenix2 uses Fusion exclusively. Phoenix3 uses proto, which according to Eric does not use Fusion, although IIRC the core of Phoenix3 uses some Fusion still (quick check: Thomas uses an optimized-PP version of fusion:: vector for phoenix3).
Heller did a helluva perf-tweaks for Phx3 to get that number for g++ (alas, not MSVC). In fairness, I did absolutely no CT perf-tweaks for both Phoenix2 and Fusion.
(** I made sure both tests have exactly the same code, so I removed the last test. I can post the exact code if need be)
OK, I retract everything I said. Fusion rulez, and Proto needs help. Sorry for the blind accusation. Let's stop this and figure out what needs to be fixed.
FWIW, there are some unit tests that outperform the compile times of Phoenix2 (with gcc), the current bad hit on compile times seem to only occur with let, lambda and switch/case expressions.
This /suggests/ to me that the core of Phx3 is sound, but that the implementation of let, lambda, and switch are heavy. But I'm not blaming Thomas. I'm just suggesting a logical place to begin an investigation.
FWIW, i experimented with different implementations, I even almost identically (as far as i could) copied the phx2 implementation. For the implementation right now I have several suspects. First of all, i think the code of the mentioned parts is very ugly (both of V2 and V3). Second of all, there some pretty severe type transformations going on, repeated calls to fusion::make_map etc. I am absolutely sure that there is quite some space for improvement.
And regardless, we should point Steven's template profiler at the code and see what it says. Thomas, do you want to give that a shot?
Yes, I can do that, I am swamped with work until the end of the week though. So if anyone wants to give some hints ... feel free to do so ...