Hi, How to explain so considerable difference in performance: g++ Cygwin vs. other compilers in tests below?
Simple C/C++ Perfometer : Copying char[] to vector (Version CS-1.0) * func_memcpy * func_copy * func_copy_with_reserve * func_transform * func_ctor * The whole program at http://thread.gmane.org/gmane.comp.lang.c++.perfometer/58 contains the following files : - copystr.h // Header file : http://article.gmane.org/gmane.comp.lang.c++.perfometer/58/ - info.cpp // Information about compiler : http://article.gmane.org/gmane.comp.lang.c++.perfometer/59/ - cps_test.cpp // Function tested : http://article.gmane.org/gmane.comp.lang.c++.perfometer/60/ - cps_main.cpp // Main program : http://article.gmane.org/gmane.comp.lang.c++.perfometer/61/ Payload code : cps_test.cpp. Housekeeping code : copystr.h, info.cpp, cps_main.cpp. ###### C++ Code Tested : BEGIN ###### // Code from http://article.gmane.org/gmane.comp.lang.c++.perfometer/60 #define STR_LEN 100 char cstr[STR_LEN]; struct char_identity { char operator()(char ch) const { return ch; } }; // ====== Function tested using Simple C++ Perfometer ====== void func_memcpy() { vector<char> vect (STR_LEN); memcpy(&vect[0], cstr, STR_LEN); } void func_copy() { vector<char> vect; copy(cstr, cstr + STR_LEN, back_inserter(vect)); } void func_copy_with_reserve() { vector<char> vect; vect.reserve(STR_LEN); copy(cstr, cstr + STR_LEN, back_inserter(vect)); } void func_transform() { vector<char> vect (STR_LEN); transform(cstr, cstr + STR_LEN, vect.begin(), char_identity()); } void func_ctor() { vector<char> vect (cstr, cstr + STR_LEN); } // ========================================================= ###### C++ Code Tested : END ######## ###### Run Log (Fragments) : BEGIN ######## >From http://article.gmane.org/gmane.comp.lang.c++.perfometer/62/ ======================================== Simple C/C++ Perfometer : Copying String Version CS-1.0 ======================================== C/C++ Performance Tests ======================= Using Simple C/C++ Perfometer (Copying char[] to vector), Version CS-1.0 http://thread.gmane.org/gmane.comp.lang.c++.perfometer/58/ (The whole program) http://article.gmane.org/gmane.comp.lang.c++.perfometer/60/ (Functions tested only) Environment ----------- Windows 2000 Professional Intel(R) Celeron(R) CPU 1.70 GHz #################################### ### Compilation with no optimization #################################### ### char[] size : 100 ### Number of repetitions : 100000 ---------------------- GNU gcc 3.3.1 (CYGWIN) ---------------------- ### CLOCKS_PER_SEC : 1000 func_memcpy : 2937 units (2.937 secs) func_copy : 14487 units (14.487 secs) func_copy_with_reserve : 4098 units (4.098 secs) func_transform : 3428 units (3.428 secs) func_ctor : 2944 units (2.944 secs) --------------------- GNU gcc 3.3.1 (MINGW) --------------------- ### CLOCKS_PER_SEC : 1000 func_memcpy : 74 units (0.074 secs) func_copy : 1117 units (1.117 secs) func_copy_with_reserve : 584 units (0.584 secs) func_transform : 303 units (0.303 secs) func_ctor : 57 units (0.057 secs) ------------------------- GNU gcc 3.3.4 (DGGPP 2.3) ------------------------- ### CLOCKS_PER_SEC : 91 func_memcpy : 11 units (0.121 secs) func_copy : 243 units (2.670 secs) func_copy_with_reserve : 121 units (1.330 secs) func_transform : 65 units (0.714 secs) func_ctor : 10 units (0.110 secs) ------------------------------- Microsoft C++ 13.00 (Unmanaged) ------------------------------- ### CLOCKS_PER_SEC : 1000 func_memcpy : 1465 units (1.465 secs) func_copy : 13202 units (13.202 secs) func_copy_with_reserve : 4609 units (4.609 secs) func_transform : 1963 units (1.963 secs) func_ctor : 1378 units (1.378 secs) ------------------------- Digital Mars C/C++ 8.40.2 ------------------------- ### CLOCKS_PER_SEC : 1000 func_memcpy : 63 units (0.063 secs) func_copy : 574 units (0.574 secs) func_copy_with_reserve : 220 units (0.220 secs) func_transform : 130 units (0.130 secs) func_ctor : 60 units (0.060 secs) ###### Run Log (Fragments) : END ########## List of the functions sorted according to performance: * func_ctor (the fastest) * func_memcpy * func_transform * func_copy_with_reserve * func_copy -- Alex Vinokur http://mathforum.org/library/view/10978.html http://sourceforge.net/users/alexvn -- Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple Problem reports: http://cygwin.com/problems.html Documentation: http://cygwin.com/docs.html FAQ: http://cygwin.com/faq/
