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diff --git a/README.md b/README.md new file mode 100644 index 0000000..679cf90 --- /dev/null +++ b/README.md @@ -0,0 +1,71 @@ +# boltzgen + +…a framework for symbolically generating optimized implementations of the Lattice Boltzmann Method. + +At the moment this is a more structured and cleaned up version of the OpenCL kernel generator employed by [symlbm_playground](https://tree.kummerlaender.eu/projects/symlbm_playground/). The goal is to build upon this foundation to provide an easy way to generate efficient code using a high level description of various collision models and boundary conditions. This should allow for easy comparision between various streaming patterns and memory layouts. + +## Features + +* BGK collision step +* D2Q9, D3Q7, D3Q19 and D3Q27 lattices with automatic weight inference +* momenta and bounce back boundary conditions +* equilibrilization and moment collection utility functions +* optimization via common subexpression elimination +* array-of-structures and structure-of-arrays memory layouts +* AB streaming pattern +* C++ and OpenCL targets +* simple CLI frontend + +## Usage + +The development and execution environment is described using a Nix expression in `shell.nix`. + +``` +> nix-shell +> ./boltzgen.py --help +usage: boltzgen.py [-h] --lattice LATTICE --layout LAYOUT --precision + PRECISION --geometry GEOMETRY --tau TAU [--disable-cse] + [--functions FUNCTIONS [FUNCTIONS ...]] + [--extras EXTRAS [EXTRAS ...]] + language + +Generate LBM kernels in various languages using a symbolic description. + +positional arguments: + language Target language (currently either "cl" or "cpp") + +optional arguments: + -h, --help show this help message and exit + --lattice LATTICE Lattice type (D2Q9, D3Q7, D3Q19, D3Q27) + --layout LAYOUT Memory layout ("AOS" or "SOA") + --precision PRECISION + Floating precision ("single" or "double") + --geometry GEOMETRY Size of the block geometry ("x:y(:z)") + --tau TAU BGK relaxation time + --disable-cse Disable common subexpression elimination + --functions FUNCTIONS [FUNCTIONS ...] + Function templates to be generated + --extras EXTRAS [EXTRAS ...] + Additional generator parameters + +> ./boltzgen.py cpp --lattice D2Q9 +\ --geometry 128:128 +\ --layout AOS +\ --precision double +\ --tau 0.52 +\ --functions default bounce_back_boundary example +\ --extras omp_parallel_for moments_vtk | tee kernel.h +void collide_and_stream( double* f_next, + const double* f_prev, + std::size_t gid) +{ + double* preshifted_f_next = f_next + gid*9; + const double* preshifted_f_prev = f_prev + gid*9; + + const double f_curr_0 = preshifted_f_prev[1161]; + const double f_curr_1 = preshifted_f_prev[1153]; + const double f_curr_2 = preshifted_f_prev[1145]; + const double f_curr_3 = preshifted_f_prev[12]; + const double f_curr_4 = preshifted_f_prev[4]; +[...] +``` |