Re: [boost] [local] Help for the Alternatives section

Subject: Re: [boost] [local] Help for the Alternatives section
From: lcaminiti (lorcaminiti_at_[hidden])
Date: 2011-03-29 09:49:49

Vicente Botet wrote:
> 
> > Message du 28/03/11 19:52
> > De : "lcaminiti" 
> > A : boost_at_[hidden]
> > Copie à : 
> > Objet : Re: [boost] [local] Help for the Alternatives section
> > 
> > 
> > Thomas Heller-7 wrote:
> > > 
> > > On Monday, March 28, 2011 07:03:46 PM lcaminiti wrote:
> > > > 
> > > > Thomas Heller-7 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/Alternatives.html
> > > > > > 
> > > > > > 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_at_sunshine ~/programming/local $ time
> ./add_phoenix
> > > > > 1e+12
> > > > > 
> > > > > real 0m6.648s
> > > > > user 0m6.643s
> > > > > sys 0m0.007s
> > > > > 
> > > > 
> > > > This is not a fare comparison because add.cpp contains also
> local
> > > blocks and
> > > > exits while add_boost_phoenix.cpp contains only local
> functions. The
> > > > comparison should be made between add_boost_local.cpp and
> > > > add_boost_phoenix.cpp (see below). The example names got a
> bit
> > > confusing and
> > > > I will rename add.cpp to add_funciton_block_exit.cpp to
> avoid similar
> > > > misunderstandings in the future.
> > > 
> > > Seriously? Did you even look at the files i attached?
> > > 
> > 
> > Ooops... no, I didn't. I have files with the exact same name in
> > sandbox/local/libs/local/examples so I assumed you attached these
> files...
> > 
> > 
> > 
> > > Are you serious? Please write real benchmarks. By executing the
> resulting 
> > > binaries of your code examples, the runtime is mainly dominated
> by process
> > > setup 
> > > and the output on stdout.
> > > 
> > > Take a look here: 
> > > https://svn.boost.org/svn/boost/trunk/libs/spirit/optimization/
> > > 
> > 
> > I have looked at the files you have attached now and I see what you
> mean.
> > Please scratch my previous benchmark numbers. I will run correct
> tests more
> > along the lines of what you suggested.
> 
> 
> Hi Lorenzo,
> 
> To complete the performance comparison I will add a hand written test
> which should be used as reference implementation.
> 
> for (size_t i = 0; i < v.size(); ++i) {
> sum += factor * num;
> }
> 
> and a non-local functor so it can be used with foreach (which seems to
> perform better than the manual for (size_t i = 0; i < v.size(); ++i) 
> 
> struct non_local_add {
> // Unfortunately, extra code to manually program the functor class.
> local_add(double& _sum, int _factor): sum(_sum), factor(_factor) {}
> 
> void operator()(double num) {
> // Body uses C++ statement syntax.
> sum += factor * num;
> std::cout << "Summed: " << sum << std::endl;
> }
> 
> private:
> // Unfortunately, cannot bind so repeat variable types.
> double& sum; // Access `sum` by (non-constant) reference.
> const int factor; // Make `factor` constant.
> } ;
> 
> int main() {
> double sum = 0.0;
> int factor = 10;
> 
> std::vector v(3);
> v[0] = 1.0; v[1] = 2.0; v[2] = 3.0;
> 
> non_local_add add(sum, factor);
> 
> // Non Local functor `add` passed as template parameter.
> std::for_each(v.begin(), v.end(), add);
> 
> std::cout << sum << std::endl;
> return 0;
> }
> 

Yes, I am already looking as the non-local functor and the local functor
without for_each as baselines. 

> In addition you can use Boost.Chrono so you measure exactly what you want
> to measure,i.e. the add instantiation + the foreach without setup and
> output.
> 

I will look into Boost.Chrono. If you had time to sketch a bit of code on
how I'd use Chrono in this case, it'd get me started. Thanks.

--Lorenzo

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