std::string copy constructor slow --------------------------------- Key: STDCXX-518 URL: https://issues.apache.org/jira/browse/STDCXX-518 Project: C++ Standard Library Issue Type: Improvement Components: 21. Strings Affects Versions: 4.1.3 Environment: gcc 4.1.2, x86_64 Reporter: Mark Brown
When thread safety is enabled in stdcxx the string copy constructor is more than ten times slower than when it's not, and twice as slow as the same copy constructor in gcc 4.1.2 on Linux (x86_64), but slightly faster than with STLport 5.1.3. The timings were done on Intel x86_64 at 2.4GHz: BUILDMODE=shared,optimized: $ time LD_LIBRARY_PATH=../lib ./string-copy 100000000 real 0m0.482s user 0m0.480s sys 0m0.000s BUILDMODE=shared,optimized,pthread: $ time LD_LIBRARY_PATH=../lib ./string-copy 100000000 real 0m10.157s user 0m10.041s sys 0m0.032s gcc 4.1.2 with -O2 -m64: $ time ./string-copy.gcc 100000000 real 0m4.280s user 0m4.260s sys 0m0.020s gcc 4.1.2 with STLport 5.1.3 (-D_REENTRANT -O2 -m64 -lpthread): $ time ./string-copy.stlport 100000000 real 0m12.479s user 0m12.473s sys 0m0.004s #include <cassert> #include <cstdlib> #include <string> int main (int argc, char *argv[]) { const unsigned long n = argc < 2 ? 0 : std::strtoul (argv [1], 0, 10); std::string strings [256]; const std::size_t num_strings = sizeof strings / sizeof *strings; for (unsigned long i = 0; i != num_strings; ++i) strings [i].assign (i, 'x'); for (unsigned long i = 0; i < n; ++i) { const std::size_t length = i % num_strings; const std::string str (strings [length]); assert (str.size () == length); } } -- This message is automatically generated by JIRA. - You can reply to this email to add a comment to the issue online.