From: stefano AT tirreno DOT it ("Stefano Gragnani") Subject: Runtime speed with GNU compilers 14 Apr 1997 16:50:59 -0700 Approved: cygnus DOT gnu-win32 AT cygnus DOT com Distribution: cygnus Message-ID: <199704142148.XAA27137.cygnus.gnu-win32@mail.tirreno.it> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Original-To: X-MSMail-Priority: Normal X-Priority: 3 X-Mailer: Microsoft Internet Mail 4.70.1155 Original-Sender: owner-gnu-win32 AT cygnus DOT com Thanks for the replies. I have compiled and runned another time the code-example with various options, the results are: 1) without options ==> 2063 seconds 2) only with the '-O3' options (with the capital "O") ==> 2362 seconds !!!!! 3) with '-O3' + '-ffast-math' ==> 113 seconds 4) with only '-ffast-math' ==> about 2000 seconds. Why with the '-O3' options the time is grater that without optimizations ? In the online documentation that I have read the '-O6' option is not documented (only the '-O1', '-O2' and 'O3' are mentioned) but it is accepted from the compiler: wich are "its optimizations"? The '-ffast-math' is not aderent to the IEEE 754 arithmetic and therefore, in general, it use is not recommended and is not good that g++ required it (plus the '-O3' or the '-O6' option) to obtain the best result (113 seconds). (The Metrowerk compiler is aderent to the IEEE 754 and is result is 125 seconds ...) If the problems are the Cygnus libraries under NT, there are other libraries for NT? Thanks Stefano Gragnani - For help on using this list (especially unsubscribing), send a message to "gnu-win32-request AT cygnus DOT com" with one line of text: "help".