Myth 1: “To understand C++, you must first learn C” -- performance aspect

Understand-C++

// https://isocpp.org/blog/2014/12/myths-1
//
// Bjarne Stroustrup.
//
// 2.  Myth 1: “To understand C++, you must first learn C”
//
// No. Learning basic programming using C++ is far easier than with C.
//
// C is almost a subset of C++, but it is not the best subset to learn first
// because C lacks the notational support, the type safety, and the easier-to-use
// standard library offered by C++ to simplify simple tasks.
//
//  Which version would you rather teach? Which version is easier to use?
// Did I really get the C version right? Are you sure? Why?
//
// Finally, which version is likely to be the most efficient? Yes, the C++ version,
// because it does not have to count the argument characters and does not use the
// free store (dynamic memory) for short argument strings.
// ---
// Look at the results at the bottom.

// Scott Meyers. std::string, SSO, and Move Semantics. Tuesday, April 10, 2012.
// http://scottmeyers.blogspot.nl/2012/04/stdstring-sso-and-move-semantics.html

// John Ahlgren. Small String Optimization and Move Operations. Friday, March 30, 2012.
// http://john-ahlgren.blogspot.nl/2012/03/small-string-optimization-and-move.html

#define SMALL  0
#define MEDIUM 1
#define LARGE  2

#ifndef SIZE
#define SIZE SMALL
#endif

#ifdef __GNUC__
# define MESSAGE( text ) GCC message ( text )
#else
# define MESSAGE( text ) message ( text )
#endif

#define TEXT1 \
    "Lorem Ipsum is simply dummy text of the printing and typesetting industry. " \
    "Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, " \
    "when an unknown printer took a galley of type and scrambled it to make a type " \
    "specimen book. It has survived not only five centuries, but also the leap into " \
    "electronic typesetting, remaining essentially unchanged. It was popularised in " \
    "the 1960s with the release of Letraset sheets containing Lorem Ipsum passages, " \
    "and more recently with desktop publishing software like Aldus PageMaker including " \
    "versions of Lorem Ipsum."

#define TEXT2 \
    "It is a long established fact that a reader will be distracted by the readable " \
    "content of a page when looking at its layout. The point of using Lorem Ipsum is " \
    "that it has a more-or-less normal distribution of letters, as opposed to using " \
    "'Content here, content here', making it look like readable English. Many desktop " \
    "publishing packages and web page editors now use Lorem Ipsum as their default " \
    "model text, and a search for 'lorem ipsum' will uncover many web sites still " \
    "in their infancy. Various versions have evolved over the years, sometimes by " \
    "accident, sometimes on purpose (injected humour and the like)."

#if __cplusplus
#pragma MESSAGE("Compiling as C++")

#include <string>
using std::string;

string compose( const string& name, const string& domain )
{
    return name + '@' + domain;
}

int main()
{
    for ( int i = 0; i < 10000; ++i )
    {
        for ( int k = 0; k < 1000; ++k )
        {
#if SIZE == SMALL
#pragma MESSAGE("Small string")
            string addr = compose( "aa", "fb.com" );
#elif SIZE == MEDIUM
#pragma MESSAGE("Medium string")
            string addr = compose( "gre", "research.att.com" );
#elif SIZE == LARGE
#pragma MESSAGE("Large string")
            string addr = compose( TEXT1, TEXT2 );
#endif
        }
    }
}

#else // __cplusplus
#pragma MESSAGE("Compiling as C")

#include <malloc.h>
#include <string.h>

char* compose( const char* name, const char* domain )
{
    char* res = malloc( strlen(name) + strlen(domain) + 2 ); // space for strings, '@', and 0
    char* p = strcpy( res, name );
    p += strlen( name );
    *p = '@';
    strcpy( p + 1, domain );
    return res;
}

int main()
{
    for ( int i = 0; i < 10000; ++i )
    {
        for ( int k = 0; k < 1000; ++k )
        {
#if SIZE == SMALL
#pragma MESSAGE("Small string")
            char* addr = compose( "aa", "fb.com" );
#elif SIZE == MEDIUM
#pragma MESSAGE("Medium string")
            char* addr = compose( "gre", "research.att.com" );
#elif SIZE == LARGE
#pragma MESSAGE("Large string")
            char* addr = compose( TEXT1, TEXT2 );
#endif
            free( addr ); // release memory when done
        }
    }
}

#endif // __cplusplus

#if 0

g++ -O2 -x c++ -std=c++03 -o main-gcc-cpp03.exe main.c
g++ -O2 -x c++ -std=c++11 -o main-gcc-cpp11.exe main.c
g++ -O2 -x c   -std=c99   -o main-gcc-c99.exe   main.c

cl -EHsc -O2 -TP -Femain-vc-cpp.exe main.c
cl -EHsc -O2 -TC -Femain-vc-c.exe   main.c

g++ --version
timemem main-gcc-cpp03
timemem main-gcc-cpp11
timemem main-gcc-c99

cl
timemem main-vc-cpp
timemem main-vc-c

--------------------------------------------------------------------------

Results for SIZE == SMALL:
    
g++ (GCC) 4.8.1

>timemem main-gcc-cpp03
Exit code      : 0
Elapsed time   : 13.19
Kernel time    : 0.00 (0.0%)
User time      : 13.17 (99.9%)
page fault #   : 753
Working set    : 2748 KB
Paged pool     : 23 KB
Non-paged pool : 4 KB
Page file size : 544 KB

>timemem main-gcc-cpp11
Exit code      : 0
Elapsed time   : 12.24
Kernel time    : 0.02 (0.1%)
User time      : 12.23 (100.0%)
page fault #   : 753
Working set    : 2744 KB
Paged pool     : 23 KB
Non-paged pool : 4 KB
Page file size : 548 KB

>timemem main-gcc-c99
Exit code      : 0
Elapsed time   : 0.89
Kernel time    : 0.02 (1.8%)
User time      : 0.86 (96.3%)
page fault #   : 693
Working set    : 2512 KB
Paged pool     : 21 KB
Non-paged pool : 4 KB
Page file size : 488 KB

Microsoft (R) C/C++ Optimizing Compiler Version 18.00.31101 for x86

>timemem main-vc-cpp
Exit code      : 0
Elapsed time   : 1.31
Kernel time    : 0.00 (0.0%)
User time      : 1.31 (99.9%)
page fault #   : 514
Working set    : 1868 KB
Paged pool     : 19 KB
Non-paged pool : 4 KB
Page file size : 412 KB

>timemem main-vc-c
Exit code      : 0
Elapsed time   : 0.67
Kernel time    : 0.02 (2.3%)
User time      : 0.66 (98.3%)
page fault #   : 511
Working set    : 1860 KB
Paged pool     : 19 KB
Non-paged pool : 4 KB
Page file size : 416 KB

#endif