OpenLB build configuration

This file sets up the necessary build flags for compiling OpenLB with

the GNU C++ compiler and sequential execution. For more complex setups

edit this file or consult the example configs provided in config/.

Basic usage:

- Edit variables to fit desired configuration

- Run make clean; make to clean up any previous artifacts and compile the dependencies

- Switch to example directory, e.g. examples/laminar/poiseuille2d

- Run make

- Start the simulation using ./poiseuille2d

Compiler to use for C++ files, change to mpic++ when using OpenMPI and GCC

CXX := g++

Compiler to use for C files (used for emebedded dependencies)

CC := gcc

Suggested optimized build flags for GCC, consult config/ for further examples

CXXFLAGS := -O3 -Wall -march=native -mtune=native

Uncomment to add debug symbols and enable runtime asserts

CXXFLAGS += -g -DOLB_DEBUG

OpenLB requires support for C++17

works in:

* gcc 9 or later (https://gcc.gnu.org/projects/cxx-status.html#cxx17)

* icc 19.0 or later (https://software.intel.com/en-us/articles/c17-features-supported-by-intel-c-compiler)

* clang 7 or later (https://clang.llvm.org/cxx_status.html#cxx17)

CXXFLAGS += -std=c++17

optional linker flags

LDFLAGS :=

Parallelization mode, must be one of: OFF, MPI, OMP, HYBRID

Note that for MPI and HYBRID the compiler also needs to be adapted.

See e.g. config/cpu_gcc_openmpi.mk

PARALLEL_MODE := OFF

optional MPI and OpenMP flags

MPIFLAGS :=

OMPFLAGS := -fopenmp

Options: CPU_SISD, CPU_SIMD, GPU_CUDA

Both CPU_SIMD and GPU_CUDA require system-specific adjustment of compiler flags.

See e.g. config/cpu_simd_intel_mpi.mk or config/gpu_only.mk for examples.

CPU_SISD must always be present.

PLATFORMS := CPU_SISD

Fundamental arithmetic data type

Common options are float or double

FLOATING_POINT_TYPE := double

Any entries are passed to the compiler as -DFEATURE_* declarations

Used to enable some alternative code paths and dependencies

FEATURES :=

Set to OFF if libz and tinyxml are provided by the system (optional)

USE_EMBEDDED_DEPENDENCIES := ON

Example build config for OpenLB using CUDA on single GPU systems

#

Tested using CUDA 11.4

#

Usage:

- Copy this file to OpenLB root as config.mk

- Adjust CUDA_ARCH to match your specifc GPU

- Run make clean; make

- Switch to example directory, e.g. examples/laminar/cavity3dBenchmark

- Run make

- Start the simulation using ./cavity3d

CXX := nvcc CC := nvcc

CXXFLAGS := -O3 CXXFLAGS += -std=c++17 --forward-unknown-to-host-compiler

PARALLEL_MODE := NONE

PLATFORMS := CPU_SISD GPU_CUDA

for e.g. RTX 30* (Ampere), see table in rules.mk for other options

CUDA_ARCH := 60

FLOATING_POINT_TYPE := float

USE_EMBEDDED_DEPENDENCIES := ON