Re: [Boost-users] g++ compilation is slow with Boost's constructs

Subject: Re: [Boost-users] g++ compilation is slow with Boost's constructs
From: OvermindDL1 (overminddl1_at_[hidden])
Date: 2010-09-10 21:37:30

On Thu, Sep 9, 2010 at 10:17 AM, Ilya Murav'jov <muravev_at_[hidden]> wrote:
> Jason Merrill пишет:
>> > On 09/08/2010 07:40 AM, Ilya Murav'jov wrote:
>>> >> Dave Abrahams пишет:
>>>> >>> G++4.5 implements O(1) template lookup, which could have a
> significant
>>>> >>> effect for Boost users.
>>> >>
>>> >> Thanks for the info. I've built gcc-4.5.1 myself and got not very
>>> >> comforting results: g++4.2 is still 'unbeaten', g++4.5 is 15% slower.
>> >
>> > Hmm, that's disappointing. Â I grabbed the source file you mentioned, but
>> > it seems to depend on other headers from your project; if you send me a
>> > preprocessed file I'll try to take a look at what's slowing it down
>> > sometime soon.
>> >
>> > Jason
>> >
>
> After some experiments I've done a clear example. It shows that
> boost::lambda::bind() invocation cost 0.1 sec. Here is the code:
>
> //////////////////// begin ////////////////////////
>
> #include <boost/lambda/bind.hpp> Â  // boost::lambda::bind
> #include <boost/function.hpp> Â  Â  Â // boost::function
>
> typedef boost::function<void()> TestFunctor;
>
> template<int value>
> struct TestStruct
> {
> };
>
> #define IMPL_DEF_(Idx, Type) void Impl ## Idx(Type) {} \
> void TestImpl ## Idx() Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  \
> { Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â \
> Â  Â TestFunctor fnr; Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  \
> Â  Â fnr = boost::lambda::bind(&Impl ## Idx, Type()); Â \
> } \
> /**/
>
> #define IMPL_DEF(Idx) IMPL_DEF_(Idx, TestStruct<Idx>)
>
> #define IMPL_DEF_10_(Idx) \
> IMPL_DEF(Idx ## 0) \
> IMPL_DEF(Idx ## 1) \
> IMPL_DEF(Idx ## 2) \
> IMPL_DEF(Idx ## 3) \
> IMPL_DEF(Idx ## 4) \
> IMPL_DEF(Idx ## 5) \
> IMPL_DEF(Idx ## 6) \
> IMPL_DEF(Idx ## 7) \
> IMPL_DEF(Idx ## 8) \
> IMPL_DEF(Idx ## 9) \
> /**/
>
> #define IMPL_DEF_10(Idx) IMPL_DEF_10_(Idx)
>
> IMPL_DEF_10(__LINE__)
> IMPL_DEF_10(__LINE__)
> IMPL_DEF_10(__LINE__)
> IMPL_DEF_10(__LINE__)
> IMPL_DEF_10(__LINE__)
> IMPL_DEF_10(__LINE__)
> IMPL_DEF_10(__LINE__)
> IMPL_DEF_10(__LINE__)
> IMPL_DEF_10(__LINE__)
> IMPL_DEF_10(__LINE__)
>
> //////////////////// end ////////////////////////
>
> It does 100 invocations of boost::lambda::bind() with various types.
> Benchmarks with "-c -g -O0 -pipe", Boost 1.44:
>
> G++ 4.2.4: 14.75 sec
> G++ 4.5.1: 09.57 sec
>
> P.S. It shows that  g++4.5 is quicker, though.  :)  Later I try to do
> examples with other constructs (BOOST_FOREACH, Boost.Range, B.Function)
> to find out where g++4.2 is better.
>
> P.S.S. I suggest to make comparison among varios compilers (i.e., clang,
> msvc, icc) with this test. It is interesting to see the quickest (don't
> forget to include your CPU).

I have an AMD Phenom II CPU, 3.2ghz, my times:

home:/home/overminddl1/projects/testingrandom# g++ -v
Using built-in specs.
Target: i486-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Ubuntu
4.4.3-4ubuntu5'
--with-bugurl=file:///usr/share/doc/gcc-4.4/README.Bugs
--enable-languages=c,c++,fortran,objc,obj-c++ --prefix=/usr
--enable-shared --enable-multiarch --enable-linker-build-id
--with-system-zlib --libexecdir=/usr/lib --without-included-gettext
--enable-threads=posix --with-gxx-include-dir=/usr/include/c++/4.4
--program-suffix=-4.4 --enable-nls --enable-clocale=gnu
--enable-libstdcxx-debug --enable-plugin --enable-objc-gc
--enable-targets=all --disable-werror --with-arch-32=i486
--with-tune=generic --enable-checking=release --build=i486-linux-gnu
--host=i486-linux-gnu --target=i486-linux-gnu
Thread model: posix
gcc version 4.4.3 (Ubuntu 4.4.3-4ubuntu5)
home:/home/overminddl1/projects/testingrandom# ~/llvm/Release/bin/clang++ -v
clang version 2.8 (trunk 113038)
Target: i386-pc-linux-gnu
Thread model: posix
home:/home/overminddl1/projects/testingrandom# time g++ test.cpp
/usr/lib/gcc/i486-linux-gnu/4.4.3/../../../../lib/crt1.o: In function `_start':
(.text+0x18): undefined reference to `main'
collect2: ld returned 1 exit status

real    0m8.504s
user    0m5.336s
sys     0m0.184s
home:/home/overminddl1/projects/testingrandom# time
~/llvm/Release/bin/clang++ test.cpp
/usr/lib/gcc/i486-linux-gnu/4.4.3/../../../../lib/crt1.o: In function `_start':
(.text+0x18): undefined reference to `main'
collect2: ld returned 1 exit status
clang: error: linker (via gcc) command failed with exit code 1 (use -v
to see invocation)

real    0m3.443s
user    0m2.524s
sys     0m0.188s

However, clang++ usually does not compile code that runs quite as fast
as g++ as of yet, but they are getting close, and yes, I know my g++
is old, it is the stock install.