// If you get a timeout, just run again. #include #include #include // Returns CPU clock cycle count since CPU powerup, useful for random numbers and calculating clock cycles :) uint64_t rdtsc() { uint32_t l, h; __asm__ __volatile__( "rdtsc" : "=a"(l), "=d"(h) ); return (uint64_t)h << 32 | l; } // I might expand this later template class ClockSpeedTest { public: template static uint64_t CalculateAverageRunTime( unsigned long long iterations, std::function f, Args... args ) { if( !f ) return -1; return CalculateRunTime( iterations, f, std::forward(args)... ) / iterations; } private: template static uint64_t CalculateRunTime( unsigned long long iterations, std::function f, Args... args ) { uint64_t startTime = rdtsc(); for( unsigned long long i = 0; i < iterations; ++i ) { f( std::forward(args)... ); } return rdtsc() - startTime; } }; // Test function 1, fastest on big inputs, good enough on small inputs std::string Separator( const std::string& s, unsigned spacing = 3, char sep = ',' ) { std::string r( s.size() + s.size() / spacing, ' ' ); std::string::size_type end = s.find_first_not_of( '0' ); end = ( end == std::string::npos ? s.size() : s.size() - end ); for( std::string::size_type i = 0, dots = 0; i < end; ++i ) { if( i != 0 && i % spacing == 0 ){ r[i + dots] = sep; ++dots; } r[i + dots] = s[s.size() - 1 - i]; } r = r.substr( 0, r.find_last_not_of( ' ' ) + 1 ); std::reverse( r.begin(), r.end() ); return r; } // Test function 2, slowest of them all for obvious reasons. std::string Separator2( const std::string& s, unsigned spacing = 3, char sep = ',' ) { std::string r; std::string::size_type end = s.find_first_not_of( '0' ); end = ( end == std::string::npos ? s.size() : s.size() - end ); for( std::string::size_type i = 0; i < end; ++i ) { if( i != 0 && i % spacing == 0 ) r = sep + r; r = s[s.size() - 1 - i] + r; } return r; } // Test function 3, also fast, close to test function 1 std::string Separator3( const std::string& s, unsigned spacing = 3, char sep = ',' ) { std::string r; r.reserve( s.size() + s.size() / spacing ); std::string::size_type end = s.find_first_not_of( '0' ); end = ( end == std::string::npos ? s.size() : s.size() - end ); for( std::string::size_type i = 0; i < end; ++i ) { if( i != 0 && i % spacing == 0 ) r += sep; r += s[s.size() - 1 - i]; } std::reverse( r.begin(), r.end() ); return r; } // test function 4, Identical to test function 1 except I replaced std::reverse with std::string's range constructor ( which may require a heap alloc ) std::string Separator4( const std::string& s, unsigned spacing = 3, char sep = ',' ) { std::string r( s.size() + s.size() / spacing, ' ' ); std::string::size_type end = s.find_first_not_of( '0' ); end = ( end == std::string::npos ? s.size() : s.size() - end ); for( std::string::size_type i = 0, dots = 0; i < end; ++i ) { if( i != 0 && i % spacing == 0 ){ r[i + dots] = sep; ++dots; } r[i + dots] = s[s.size() - 1 - i]; } r = r.substr( 0, r.find_last_not_of( ' ' ) + 1 ); return {r.rbegin(), r.rend()}; } uint64_t randomBetween( uint64_t min, uint64_t max ) { return min + rdtsc() % ( max + 1 - min ); } int main() { constexpr unsigned long long ITERATIONS = 100000; std::string s; std::generate_n( std::back_inserter( s ), randomBetween( 8, 20 ), [](){ return "0123456789"[ rdtsc() % 10 ]; } ); std::cout << "Test string: " << s << "\n\n"; using Type = ClockSpeedTest; std::cout << "Test function 1 runtime: " << Separator( std::to_string( Type::CalculateAverageRunTime( ITERATIONS, Separator , s, 3, ',' ) ) ) << " clock cycles\n"; std::cout << "Test function 2 runtime: " << Separator( std::to_string( Type::CalculateAverageRunTime( ITERATIONS, Separator2, s, 3, ',' ) ) ) << " clock cycles\n"; std::cout << "Test function 3 runtime: " << Separator( std::to_string( Type::CalculateAverageRunTime( ITERATIONS, Separator3, s, 3, ',' ) ) ) << " clock cycles\n"; std::cout << "Test function 4 runtime: " << Separator( std::to_string( Type::CalculateAverageRunTime( ITERATIONS, Separator4, s, 3, ',' ) ) ) << " clock cycles\n\n"; std::cout << Separator( s, 3 ) << '\n' << Separator( s, 3, ' ' ) << '\n' << Separator( s, 4 ) << '\n'; }

Function Speed Test