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copied!<p>Benchmark data for the code provided in the question:</p> <h2>On ideone (gcc 4.3.4):</h2> <ul> <li>stringstreams: 4.4 MB/s</li> <li>sprintf: 25.0 MB/s</li> <li><a href="http://ideone.com/SsEUW">mine (Ben Voigt)</a>: 55.8 MB/s</li> <li><a href="http://ideone.com/VpKO3">Timo</a>: 58.5 MB/s</li> <li><a href="http://ideone.com/0uhhX">user434507</a>: 199 MB/s</li> <li><a href="http://ideone.com/VLUco">user434507's Ben-Timo-507 hybrid</a>: 263 MB/s</li> </ul> <h2>Core i7, Windows 7 64-bit, 8 GB RAM, Visual C++ 2010 32-bit:</h2> <p><code>cl /Ox /EHsc</code></p> <ul> <li>stringstreams: 3.39 MB/s, 3.67 MB/s</li> <li>sprintf: 16.8 MB/s, 16.2 MB/s</li> <li>mine: 194 MB/s, 207 MB/s (with PGO enabled: 250 MB/s)</li> </ul> <h2>Core i7, Windows 7 64-bit, 8 GB RAM, Visual C++ 2010 64-bit:</h2> <p><code>cl /Ox /EHsc</code></p> <ul> <li>stringstreams: 4.42 MB/s, 4.92 MB/s</li> <li>sprintf: 21.0 MB/s, 20.8 MB/s</li> <li>mine: 238 MB/s, 228 MB/s</li> </ul> <h2>Core i7, Windows 7 64-bit, 8 GB RAM, cygwin gcc 4.3.4:</h2> <p><code>g++ -O3</code></p> <ul> <li>stringstreams: 2.19 MB/s, 2.17 MB/s</li> <li>sprintf: 13.1 MB/s, 13.4 MB/s</li> <li>mine: 30.0 MB/s, 30.2 MB/s</li> </ul> <p><strong>edit</strong>: I was gonna add my own answer, but the question was was closed so I'm adding it here. :) I wrote my own algorithm and managed to get a decent improvement over Ben's code, though I only tested it in MSVC 2010. I also made a benchmark of all the implementations presented so far, using the same testing setup that was in Ben's original code. -- Timo</p> <h2>Intel Q9450, Win XP 32bit, MSVC 2010</h2> <p><code>cl /O2 /EHsc</code></p> <ul> <li>stringstream: 2.87 MB/s</li> <li>sprintf: 16.1 MB/s</li> <li>Ben: 202 MB/s</li> <li>Ben (unsigned buffer): 82.0 MB/s</li> <li>ergosys (updated version): 64.2 MB/s</li> <li>user434507: 172 MB/s</li> <li>Timo: 241 MB/s</li> </ul> <p>-</p> <pre><code>const char digit_pairs[201] = { "00010203040506070809" "10111213141516171819" "20212223242526272829" "30313233343536373839" "40414243444546474849" "50515253545556575859" "60616263646566676869" "70717273747576777879" "80818283848586878889" "90919293949596979899" }; static const int BUFFER_SIZE = 11; std::string itostr(int val) { char buf[BUFFER_SIZE]; char *it = &buf[BUFFER_SIZE-2]; if(val>=0) { int div = val/100; while(div) { memcpy(it,&digit_pairs[2*(val-div*100)],2); val = div; it-=2; div = val/100; } memcpy(it,&digit_pairs[2*val],2); if(val<10) it++; } else { int div = val/100; while(div) { memcpy(it,&digit_pairs[-2*(val-div*100)],2); val = div; it-=2; div = val/100; } memcpy(it,&digit_pairs[-2*val],2); if(val<=-10) it--; *it = '-'; } return std::string(it,&buf[BUFFER_SIZE]-it); } std::string itostr(unsigned int val) { char buf[BUFFER_SIZE]; char *it = (char*)&buf[BUFFER_SIZE-2]; int div = val/100; while(div) { memcpy(it,&digit_pairs[2*(val-div*100)],2); val = div; it-=2; div = val/100; } memcpy(it,&digit_pairs[2*val],2); if(val<10) it++; return std::string((char*)it,(char*)&buf[BUFFER_SIZE]-(char*)it); } </code></pre>

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