| ▼Data Model | Defining topology instances and fields |
| Legion Data | Owning wrappers for Legion objects |
| Backend Data | Direct data storage |
| Launch maps | Selecting topology colors to send to tasks |
| Topology implementation | These types are movable but may not be copyable |
| ▼Execution Model | Launching tasks and kernels |
| Reduction Operations | Types to use with reduce, reduceall, and reduction_accessor |
| Kernels | Local concurrent operations |
| Legion Execution | Potentially remote task execution |
| MPI Execution | Direct task execution |
| Logging | Configurable, parallel logging |
| ▼I/O | Checkpointing |
| Legion I/O | |
| ▼Runtime Model | Environmental information and tools for organizing applications |
| Control Model | Types for defining, extending, and executing control-flow graphs |
| HPX Runtime | Global state |
| Legion Runtime | State for and control of the Legion runtime |
| MPI Runtime | Global state |
| ▼Topologies | Generic topology categories and tools for specializing them |
| Simple data | Simple parallel data access |
| Predefined specializations | Specializations for topologies so simple that no others are needed |
| Multi-dimensional Array | Configurable multi-dimensional array topology |
| N-dimensional Tree | Binary, Quad and Oct Tree topology |
| Particle Set | Supports non-interacting particle methods |
| Unstructured Mesh | Configurable unstructured mesh interface |
| GPU utilities | Containers with fixed size to use on GPUs |
| ▼Utilities | Non-domain-specific infrastructure |
| Profiling | Markers for categorizing performance measurements |
| Filling Curves | Space-filling curve, key generators |
| KDTree | KDTree based search utilities |
| Point | Spatial representation of a point based on dimensioned_array |
| Graphviz Support | Wrapper for libcgraph |
| MPI | These require MPI tasks, not the MPI backend |
| Serialization | Serialization without default constructibility |
| Unit Testing | Unit test framework much like Google Test but with task support |
| Ranges | Range and iterator tools, mostly backported from the standard library |
| Configuration | FleCSI Configuration |
| Hpx-execution |