#include <iostream>
#include <time.h>

template< typename T, int iSize, int jSize >
struct array_view 
{
    typedef T array_type [iSize][jSize];

    typedef T & result_type;

    array_type & arr;

    array_view ( array_type & src ) : arr (src) { }

    array_view & operator = ( array_view const & rhs );

    template< class Expr >
    array_view & operator = ( Expr const & rhs ) { 
        for ( int i=0; i<iSize; ++i ) for ( int j=0; j<jSize; ++j ) arr[i][j]=rhs(i,j);
        return *this;
    }


    result_type operator () ( int i, int j ) const { return this->arr[i][j]; }

};

template< int iSize, int jSize, typename T >
inline array_view<T,iSize,jSize> matrix ( T (&src) [iSize][jSize] ) { return array_view<T,iSize,jSize> (src); }

template< typename R, typename T1, typename T2 >
struct add_expr {
    T1 const & a;
    T2 const & b;

    add_expr ( T1 const & x, T2 const & y ) : a(x), b(y) {}

    R operator () ( int i, int j ) const { return a(i,j)+b(i,j); }
};

template< typename R, typename T1, typename T2 >
inline add_expr<R,T1,T2> add ( T1 const & x, T2 const & y ) {
    return add_expr<R,T1,T2> (x,y);
}


template< int count, int si, int sj >
void test () {
    int a [si][sj];
    int x [si][sj];
    int y [si][sj];
    int z [si][sj];
    int s = 0;
    for ( int u=0; u<si; ++u ) for ( int v=0; v<sj; ++v, ++s ) { a[u][v] = y[u][v] = x[u][v] = z[u][v] = s; }

    {
    time_t b = time(0);
    for ( int c=0; c<count; ++c ) for ( int u=0; u<si; ++u ) for ( int v=0; v<sj; ++v ) a[u][v] = x[u][v]+y[u][v]+z[u][v]+a[u][v];
    time_t e = time(0);
    std::cout << "array: " << difftime (e,b) << std::endl;
    }

    {
    time_t b = time(0);
    for ( int c=0; c<count; ++c ) matrix(a) = add<int> ( matrix(x),add<int>(matrix(y),add<int>(matrix(z),matrix(a))));
    time_t e = time(0);
    std::cout << "expression: " << difftime (e,b) << std::endl;
    }

}

int main ()
{
    test <400000000,3,3> ();
}

NB>вот простенький исходник. можешь запустить?

NB>#include <iostream>
NB>#include <boost/progress_timer.hpp>
// <SNIP>
NB>template< int count, int si, int sj >
NB>void test () {
NB>    int a [si][sj];
NB>    int x [si][sj];
NB>    int y [si][sj];
NB>    int z [si][sj];
NB>    int s = 0;
NB>    for ( int u=0; u<si; ++u ) for ( int v=0; v<sj; ++v, ++s ) { a[u][v] = y[u][v] = x[u][v] = z[u][v] = s; }

NB>    {
        boost::progress_timer t;
NB>    // time_t b = time(0);
NB>    for ( int c=0; c<count; ++c ) for ( int u=0; u<si; ++u ) for ( int v=0; v<sj; ++v ) a[u][v] = x[u][v]+y[u][v]+z[u][v]+a[u][v];
NB>    // time_t e = time(0);
NB>    std::cout << "array: ";
NB>    }

NB>    {
        boost::progress_timer t;
NB>    // time_t b = time(0);
NB>    for ( int c=0; c<count; ++c ) matrix(a) = add<int> ( matrix(x),add<int>(matrix(y),add<int>(matrix(z),matrix(a))));
NB>    // time_t e = time(0);
NB>    std::cout << "expression: ";
NB>    }

NB>}

NB>int main ()
NB>{
NB>    test <400000000,3,3> ();
NB>}
NB>

zaufi tests # g++ --version
i686-pc-linux-gnu-g++ (GCC) 3.4.6 (Gentoo 3.4.6-r1, ssp-3.4.5-1.0, pie-8.7.9)
Copyright (C) 2006 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

zaufi tests # g++ -O3 -o mt mt.cc
zaufi tests # ./mt
array: 9.88 s

expression: 20.03 s

zaufi tests # g++ -fomit-frame-pointer -O3 -o mt mt.cc
zaufi tests # ./mt
array: 9.47 s

expression: 18.10 s

zaufi tests # g++-4.1.1 -fomit-frame-pointer -O3 -o mt mt.cc
zaufi tests # ./mt
array: 5.88 s

expression: 5.93 s

zaufi tests # g++-4.1.1 -ftree-vectorize -fomit-frame-pointer -O3 -o mt mt.cc
zaufi tests # ./mt
array: 5.87 s

expression: 5.93 s

zaufi tests # uname -a
Linux zaufi 2.6.17-gentoo-r4 #2 PREEMPT Wed Aug 16 20:59:43 MSD 2006 i686 Intel(R) Pentium(R) 4 CPU 3.00GHz GenuineIntel GNU/Linux
zaufi tests #

zaufi tests # g++-4.1.1 -O3 -o mt mt.cc
zaufi tests # ./mt
array: 5.89 s

expression: 5.90 s

zaufi tests # g++-4.1.1 -ftree-vectorize -fomit-frame-pointer -O3 -o mt mt.cc
zaufi tests # ./mt
array: 5.91 s

expression: 5.94 s

zaufi tests # g++-4.1.1 -fomit-frame-pointer -O3 -o mt mt.cc
zaufi tests # ./mt
array: 5.89 s

expression: 5.93 s

zaufi tests # ./mt
array: 5.90 s

expression: 5.94 s

zaufi tests # g++-4.1.1 -O3 -o mt mt.cc
zaufi tests # ./mt
array: 5.90 s

expression: 5.90 s

zaufi tests # g++-4.1.1 -O3 -o mt mt.cc
zaufi tests # ./mt
array: 5.91 s

expression: 5.91 s

zaufi tests # ./mt
array: 5.88 s

expression: 5.90 s

zaufi tests # ./mt
array: 5.90 s

expression: 5.89 s

zaufi tests #

Z>>zaufi tests # g++-4.1.1 -fomit-frame-pointer -O3 -o mt mt.cc
Z>>zaufi tests # ./mt
Z>>array: 5.88 s

Z>>expression: 5.93 s

Z>>

NB>спасибо. а то я уж было совсем в гсс разочаровался

zaufi tests # g++-4.1.1 -funroll-all-loops -O3 -o mt mt.cc
zaufi tests # ./mt
array: 5.02 s

expression: 5.28 s

zaufi tests # g++-4.1.1 -fpeel-loops -O3 -o mt mt.cc
zaufi tests # ./mt
array: 5.03 s

expression: 5.26 s

zaufi tests # g++-4.1.1 -fprofile-arcs -fprofile-values -ftest-coverage -O3 -o mt mt.cc
zaufi tests # ./mt
array: 8.66 s

expression: 8.75 s

zaufi tests # g++-4.1.1 -fprofile-use -O3 -o mt mt.cc
zaufi tests # ./mt
array: 5.03 s

expression: 5.26 s

zaufi tests #