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

11 Sep 2010

      On Fri, Sep 10, 2010 at 7:38 PM, OvermindDL1  wrote:
...
On Fri, Sep 10, 2010 at 7:37 PM, OvermindDL1  wrote:
...
On Thu, Sep 9, 2010 at 10:17 AM, Ilya Murav'jov  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.  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
#include       // boost::function
typedef boost::function TestFunctor;
template<int value>
struct TestStruct
{
};
#define IMPL_DEF_(Idx, Type) void Impl ## Idx(Type) {} \
void TestImpl ## Idx()                           \
{                                                \
   TestFunctor fnr;                           \
   fnr = boost::lambda::bind(&Impl ## Idx, Type());  \
} \
/**/
#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.
Guess I should use the same parameters you did, here it is:
home:/home/overminddl1/projects/testingrandom# time g++ test.cpp -c -g -O0 -pipe
real    0m9.404s
user    0m5.500s
sys     0m1.608s
home:/home/overminddl1/projects/testingrandom# time
~/llvm/Release/bin/clang++ test.cpp -c -g -O0 -pipe
real    0m4.644s
user    0m2.948s
sys     0m0.240s
And compiling it in MSVC2k5 I got:
Release:
    Build Time 1:28
Debug:
    Build Time 1:00

In MSVC2k5 I was using WinXP 32-bit, for clang++/g++ I was using
Ubuntu 10.04 in a virtual machine with hardware virtualization enabled
on top of this WinXP 32-bit machine.