To get started with Legion, you’ll need:
- Linux, macOS, or another Unix
- A C++ 98 (or newer) compiler (GCC, Clang, Intel, or PGI) and GNU Make
- Optional: Python 2.7 (used for profiling/debugging tools)
- Optional: CUDA 5.0 or newer (for NVIDIA GPUs)
- Optional: GASNet (for networking, see installation instructions)
- Optional: LLVM 3.5-3.9 (for dynamic code generation)
- Optional: HDF5 (for file I/O)
Download Legion from Github:
To test, find an example you’d like to try and run
make. For example:
The top-level contents of the repository include:
tutorial: Source code for the tutorials.
examples: Larger examples for advanced programming techniques.
apps: Several complete Legion applications.
language: The Regent programming language compiler and examples.
runtime: The core runtime components:
legion: The Legion runtime itself (see
realm: The Realm low-level runtime (see
mappers: Several mappers, including the default mapper (see
tools: Miscellaneous tools:
The rest of this page covers how to begin using the Legion runtime.
The Legion Makefile includes several variables which influence the
build. These may either be set in the environment (e.g.
make) or at the top of each application’s Makefile.
DEBUG=<0,1>: controls optimization level and enables various dynamic checks which are too expensive for release builds.
OUTPUT_LEVEL=<level_name>: controls the compile-time logging level.
USE_CUDA=<0,1>: enables CUDA support. If enabled,
CUDA_TOOLKITHOME) should be set to the CUDA install location (e.g.
USE_GASNET=<0,1>: enables GASNet support (see installation instructions). If enabled,
GASNET_ROOT) should be set to the GASNet installation location, and
CONDUITmust be set to the desired GASNet conduit (e.g. ibv, gemini, aries).
USE_LLVM=<0,1>: enables LLVM support. If enabled, and an
llvm-configbinary is not in your path, specify its location with
USE_HDF=<0,1>: enables HDF5 support. If enabled, and HDF5 is not installed in the standard include/library directories, specify the install location using
In addition to Makefile variables, compilation is influenced by a
number of build flags. These flags may be added to the environment
CC_FLAGS (or again set inside the Makefile).
CC_FLAGS=-DLEGION_SPY: enables Legion Spy.
CC_FLAGS=-DPRIVILEGE_CHECKS: enables extra privilege checks.
CC_FLAGS=-DBOUNDS_CHECKS: enables dynamic bounds checks.
Legion and Realm accept command-line arguments for various runtime parameters. Below are some of the more commonly used flags:
-level <category>=<int>: sets logging level for
-logfile <filename>: directs logging output to
-ll:cpu <int>: CPU processors to create per process
-ll:gpu <int>: GPU processors to create per process
-ll:util <int>: utility processors to create per process
-ll:csize <int>: size of CPU DRAM memory per process (in MB)
-ll:gsize <int>: size of GASNet global memory available per process (in MB)
-ll:rsize <int>: size of GASNet registered RDMA memory available per process (in MB)
-ll:fsize <int>: size of framebuffer memory for each GPU (in MB)
-ll:zsize <int>: size of zero-copy memory for each GPU (in MB)
-lg:window <int>: maximum number of tasks that can be created in a parent task window
-lg:sched <int>: minimum number of tasks to try to schedule for each invocation of the scheduler
The default mapper also has several flags for controlling the default mapping.
default_mapper.cc for more details.
Now that a working version of Legion has been established we recommend that users follow the tutorials to begin using Legion.