This page should get you started with writing your own computer simulations with LibGeoDecomp: build the library, write a simple Hello World application, then tune it for performance. Documentation on the library's internals can be found at the bottom.
If you came here, you will probably have a reasonably clear picture of what LibGeoDecomp does. If not, then have a look at this short write up or at these slides. The following passages will guide you through the process of writing a LibGeoDecomp-based simulation code. For other examples please see the codes that come with LibGeoDecomp.
If you've already installed the library, then you may wish to
compile a program using it. You can use pkg-config to
auto-magically set the correct compiler flags, e.g.
via g++ `pkg-config --cflags --libs libgeodecomp`
test.cpp -o test. Just make sure that the install path
is found by pkg-config. If not, you may need to
set PKG_CONFIG_PATH.
First download and unpack a tarball
of LibGeoDecomp. Instead of a configure script we
use CMake to customize the build. The listing on the right shows
how to build/install/test the library. Run it from your
LibGeoDecomp directory. It performs an out-of-source
build, meaning that your source tree will not be cluttered by
a surge of object files.
make will also compile the examples found
in src/examples. The executables will be written
to their respective subdirectories
in $BUILDDIR/examples. Which examples get built
depends on the features you've selected via CMake.
BUILD_DIR=build/`uname -ms | sed s/\ /-/g` mkdir -p $BUILD_DIR cd $BUILD_DIR cmake ../../src make make test make install
By default LibGeoDecomp will be installed
to /usr/local. That may be undesirable on systems
where you don't have root access. It is perfectly fine to tell
CMake that it should install the library in your home
directory by specifying the CMAKE_INSTALL_PREFIX.
CMake will try to detect reasonable defaults for your host.
However, sometimes you may wish to opt-out of some features.
These are controlled by the FEATURE_FOO flags.
This may come in handy for instance if you have a CUDA capable
GPU installed, but don't want to use its OpenCL drivers.
A list of other configurable options is available when running CMake.
# install in my home dir: cmake -D CMAKE_INSTALL_PREFIX="/home/gentryx/libgeodecomp_install" ../../src # turn off QT and MPI: cmake -D FEATURE_QT=false -D FEATURE_MPI=false ../../src # enforce CUDA, but switch off OpenCL: cmake -D FEATURE_CUDA=true -D FEATURE_OPENCL=false ../../src # select Intel's C++ compiler (icpc): cmake -D CMAKE_CXX_COMPILER=icpc ../../src # switch off some annoying warnings of icpc: cmake -D ADDITIONAL_COMPILE_FLAGS:STRING="-Wall -Wno-sign-compare -wd981 -wd1418" ../../src
This section will detail how to write your first simulation code using LibGeoDecomp and how to tune it for optimum performance. It's not finished yet, so please refer to the examples in the library's source .
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