Fortran Programming Language :: compiler flags for gfortran on Intel Xeon 64-bit wkstation


	compiler flags for gfortran on Intel Xeon 64-bit wkstation I am trying to port my old code to my new Intel Quad Core Xeon workstation with two "clovertown" processors. I have a 64-bit Linux OS installed (Ubuntu 7.04) and I'm trying to use gfortran 4.1.2. Several questions: 1) I'm trying to install LAPACK 3.1.1. I have downloaded the precompiled ATLAS 3.6.0 library "Linux_HAMMER64SSE2_2", and was going to link against it. What compiler flags should I use? 2) I am trying to run a code written in standard f90. It does Monte Carlo simulation so optimum speed is critical. What compiler flags should I use? Note my code also uses fftw which I downloaded and installed. In my old "32-bit" machine the flags I used where: -O3 - march=pentium4. What should I use for the "64-bit" machine? Just reading the gcc manual it seams the it should be -O3 -m64, is there any -march or -mtune parameters that I should consider? The Xeon Clovertown processor can apparently use MMX,SSE,SSE2,SSE3,SSSE3 and EM64T instructions, should I use -march=nocona? Any help would be appreciated Manuel - Hide quoted text - mjm2@columbia.edu wrote: > I am trying to port my old code to my new Intel Quad Core Xeon > workstation with two "clovertown" processors. I have a 64-bit Linux OS > installed (Ubuntu 7.04) and I'm trying to use gfortran 4.1.2. > Several questions: > 1) I'm trying to install LAPACK 3.1.1. I have downloaded the > precompiled ATLAS 3.6.0 library "Linux_HAMMER64SSE2_2", and was going > to link against it. What compiler flags should I use? > 2) I am trying to run a code written in standard f90. It does Monte > Carlo simulation so optimum speed is critical. What compiler flags > should I use? Note my code also uses fftw which I downloaded and > installed. > In my old "32-bit" machine the flags I used where: -O3 - > march=pentium4. What should I use for the "64-bit" machine? Just > reading the gcc manual it seams the it should be -O3 -m64, is there > any -march or -mtune parameters that I should consider? The Xeon > Clovertown processor can apparently use MMX,SSE,SSE2,SSE3,SSSE3 and > EM64T instructions, should I use -march=nocona? That's what I use when compiling stuff with gcc. - Hide quoted text - > Any help would be appreciated > Manuel Hi, On May 24, 5:47 pm, mjm2@columbia.edu wrote: > Several questions: > In my old "32-bit" machine the flags I used where: -O3 - > march=pentium4. What should I use for the "64-bit" machine? Just > reading the gcc manual it seams the it should be -O3 -m64, is there It should already default to -m64 on x86-64 machines. > any -march or -mtune parameters that I should consider? Depending what Ubuntu did, using -march=native could work. (I think it was added in GCC 4.2, but several distributions had it already earlier.) This enables the right -march* for that processor. > The Xeon > Clovertown processor can apparently use MMX,SSE,SSE2,SSE3,SSSE3 and > EM64T instructions, should I use -march=nocona? Yes. Note that this does not imply SSSE3. -mssse3 exists, but only in the GCC 4.3 developer versions. (Unless your distribution did backport this - mine did for 4.1.x.) I personally like to use -ftree-vectorize, which should speed up calculations. I think GCC 4.2 is faster (especially gfortran) than 4.1. Ubuntu might provide some optional 4.2 packages. (openSUSE does so in Factory and via the build service for older distributions; at http://gcc.gnu.org/wiki/GFortranBinaries are also 4.2 and 4.3 binaries available.) Tobias > It does Monte Carlo simulation so optimum speed is critical. It's funny how different can be the points of view of people doing essentialy the same kind of thing. I also work with Monte Carlo simulations, and I would have said something more like: "It does Monte Carlo simulation so calculation precision is critical". > What compiler flags should I use? Note my code also uses fftw which I > downloaded and installed. Have you studied how your overall performance is dependent of BLAS/LAPACK and FFTW speed? Working on speed optimization before you actually profile the code is always a bet. About the details of the optimization flags, other people have answered. In the end, if speed is really that valuable to you, you might want to look at optimization flags selection tools like Acovea (http://www.coyotegulch.com/products/acovea/ ; I have no interest in that product myself, but find the idea pleasant). -- FX "Tobias Burnus" <bur@net-b.de> wrote in message news:1180024631.724192.174360@q69g2000hsb.googlegroups.com... > It should already default to -m64 on x86-64 machines. Not in osx, and -m64 isn't even available in xp-x64. -- write(,) transfer((/17.392111325966148d0,6.5794487871554595D-85, & 6.0134700243160014d-154/),(/'x'/)); end