On Tue, Dec 16, 2008 at 12:00 PM, Denis Koroskin <2kor...@gmail.com> wrote: > On Tue, 16 Dec 2008 05:28:16 +0300, Bill Baxter <wbax...@gmail.com> wrote: > >> On Tue, Dec 16, 2008 at 11:09 AM, Andrei Alexandrescu >> <seewebsiteforem...@erdani.org> wrote: >>> >>> Jarrett Billingsley wrote: >>>> >>>> On Sat, Dec 13, 2008 at 11:16 AM, Tomas Lindquist Olsen >>>> <to...@famolsen.dk> wrote: >>>>> >>>>> I tried this out with Tango + DMD 1.033, Tango + LDC r847 and GCC >>>>> 4.3.2, >>>>> my >>>>> timings are as follows, best of three: >>>>> >>>>> $ dmd bench.d -O -release -inline >>>>> long arith: 55630 ms >>>>> nested loop: 5090 ms >>>>> >>>>> >>>>> $ ldc bench.d -O3 -release -inline >>>>> long arith: 13870 ms >>>>> nested loop: 120 ms >>>>> >>>>> >>>>> $ gcc bench.c -O3 -s -fomit-frame-pointer >>>>> long arith: 13600 ms >>>>> nested loop: 170 ms >>>>> >>>>> >>>>> My cpu is: Athlon64 X2 3800+ >>>>> >>>> >>>> Go LDC! >>>> >>>> I hope bearophile will eventually understand that DMD is not good at >>>> optimizing code, and so comparing its output to GCC's is ultimately >>>> meaningless. >>> >>> I must have missed the memo. How is dmd not good at optimizing code? >>> Without >>> knowing many details about it, my understanding is that dmd performs >>> common >>> optimization reasonably well and that this particular problem has to do >>> with >>> the long division routine. >> >> It's pretty well proven that for floating point code, DMD tends to >> generate code about 50% slower than GCC. >> >> --bb > > But other than that it is pretty good.
Yep, it's more than 100x faster than a straightforward Python ports of similar code, for instance. (I did some benchmarking using a D port of the Laplace solver here http://www.scipy.org/PerformancePython -- I think bearophile did these comparisons again himself more recently, too). There I saw DMD about 50% slower than g++. But I've seen figures in the neighborhood of 50% come up a few times since then in other float-intensive benchmarks, like the raytracer that someone ported from c++. So it is certainly fast. But one of the draws of D is precisely that, that it is fast. If you're after code that runs as fast as possible, 50% slower than the competition is plenty justification for to go look elsewhere for your high-performance language. A 50% hit may not really be relevant at the end of the day, but I know I used to avoid g++ like the plague because even it's output isn't that fast compared to MSVC++ or Intel's compiler, even though the difference is maybe only 10% or so. I was working on interactive fluid simulation, so I wanted every bit of speed I could get out of the processor. With interactive stuff, a 10% difference really can matter, I think. > And man, it is so fast! You mean compile times? --bb
