Is your windows compiler doing automatic parallelization by chance?
Twice as fast on a dual core processor is a bit too coincidental. :-)
On 3/8/07, Shane R <crazguy22@hotmail.com> wrote:
> Hi,
>
> I hope this is the appropriate forum. Please direct me to the correct one if
> it is not.
>
> I am trying to optimize a c++ application that I ported from a windows
> system to Linux.
> The app is a terminal based application that does some one time file io at
> the start then runs completely in memory. After the one time io the app runs
> successive timed epochs on the same data in Windows as Linux. The app is a
> program that runs some code for doing non-linear optmization (math stuff).
>
> The reason why I am posting is that I timed the time it takes for the
> application to complete an epoch. It take twice as long in Linux as
> windows?!?!
>
> My system is an Intel Centrino Duo with 2gigs of ram. The application is
> only using a fraction of available memory in windows and linux. The
> application is single-threaded in both.
>
> I am using Visual Studio 2003 in Windows and when I type gcc -v I get:
> Target: i486-linux-gnu
> Configured with: ../src/configure -v
> --enable-languages=c,c++,fortran,objc,obj-c++,treelang --prefix=/usr
> --enable-shared --with-system-zlib --libexecdir=/usr/lib
> --without-included-gettext --enable-threads=posix --enable-nls
> --program-suffix=-4.1 --enable-__cxa_atexit --enable-clocale=gnu
> --enable-libstdcxx-debug --enable-mpfr --enable-checking=release
> i486-linux-gnu
> Thread model: posix
> gcc version 4.1.2 20060928 (prerelease) (Ubuntu 4.1.1-13ubuntu5)
>
>
>
> I am currently using these g++ options:
>
> CFLAGS = -o3 -O3 -march=pentium4 -ffast-math -funroll-loops -Wall
> -Wno-return-type
>
> But I have tried every permutation of the above options to virtually no
> effect
>
> The average run time of an epoch in windows is about 3000 milliseconds while
> the average run time of an epoch in Linux is 6000!
>
> I don't know if it matters but I am doing calls to the rand() function in
> both my windows and linux apps.
>
> On another note does anyone have any experience with the Intel drop in
> replacement for GCC?
>
> Thanks in advance for any help,
>
> Shane
>
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--
Lawrence Crowl