On Mon, Mar 28, 2011 at 2:50 AM, Thomas Heller <thom.heller@googlemail.com> wrote:
On Monday, March 28, 2011 05:25:13 AM Jeremy Maitin-Shepard wrote:
On 03/26/2011 03:19 PM, Lorenzo Caminiti wrote:
Hello all,
I am updating Boost.Local docs and I could use a some help in getting the Alternatives section right
http://svn.boost.org/svn/boost/sandbox/local/libs/local/doc/html/boost_local...
You might include compile time and run time benchmarks, information about error message quality, and polymorphic capabilities. Additionally, you might note that with C++0x local classes can be used with templates.
Just did a quick test ... code is attached ...
$ time g++ -O3 -I. -Wall -Wextra add.cpp -o add
real 0m0.657s user 0m0.583s sys 0m0.067s
$ time ./add 1e+12
real 0m35.641s user 0m35.618s sys 0m0.017s
$ time g++ -O3 -I. -Wall -Wextra add_boost_phoenix.cpp -o add_phoenix
real 0m3.385s user 0m3.160s sys 0m0.217s thomas@sunshine ~/programming/local $ time ./add_phoenix 1e+12
real 0m6.648s user 0m6.643s sys 0m0.007s
I have done an (hopefully more correct) benchmark of Boost.Local performances compared with the alternative methods -- please check my doing :) In summary: 1) Boost.Phoenix, global functors, and local functors run in ~15s. 2) Boost.Lambda runs in ~40s. 3) Boost.Local runs in ~53s. 4) I don't have a C++0x lambda compiler so I could not benchmark C++0x lambdas. I don't know why Boost.Lambda takes longer than 1). Boost.Local seems to take longer than 1) because of the extra virtual function call introduced by the trick that allows to pass the local struct as a template parameter -- I will follow up with another email to explain this point in detail. ANALYSIS The basic code looks like this (see attachments): #define N 10000 int main() { double sum = 0.0; int factor = 10; void BOOST_LOCAL_FUNCTION_PARAMS( (const double& num) (bind& sum) (const bind& factor) ) { sum += factor * num; } BOOST_LOCAL_FUNCTION_NAME(add) std::vector<double> v(N * 100); std::fill(v.begin(), v.end(), 10); for (size_t n = 0; n < N; ++n) { std::for_each(v.begin(), v.end(), add); } std::cout << sum << std::endl; return 0; } BOOST LOCAL $ time g++ -O3 -I../../.. -Wall -Wextra benchmark_boost_local.cpp real 0m8.330s user 0m1.166s sys 0m1.463s $ time ./a 1e+12 real 0m52.735s user 0m52.109s sys 0m0.077s GLOBAL FUNCTOR $ time g++ -O3 -I../../.. -Wall -Wextra benchmark_global_functor.cpp real 0m5.302s user 0m0.573s sys 0m0.560s $ time ./a 1e+12 real 0m15.167s user 0m14.499s sys 0m0.030s LOCAL FUNCTOR (manual for-loop instead of for_each) $ time g++ -O3 -I../../.. -Wall -Wextra benchmark_local_functor.cpp real 0m5.476s user 0m0.510s sys 0m0.730s $ time ./a 1e+12 real 0m15.392s user 0m14.686s sys 0m0.108s BOOST LAMBDA $ time g++ -O3 -I../../.. -Wall -Wextra benchmark_boost_lambda.cpp real 0m6.631s user 0m0.792s sys 0m1.199s $ time ./a 1e+12 real 0m39.855s user 0m38.905s sys 0m0.061s BOOST PHOENIX $ time g++ -O3 -I../../.. -Wall -Wextra benchmark_boost_phoenix.cpp real 0m14.004s user 0m3.761s sys 0m3.543s $ time ./a 1e+12 real 0m15.727s user 0m14.921s sys 0m0.030s -- Lorenzo