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Choose and verify a backend
Fermion selects an optimized native CPU runtime where available and a PyTorch reference path elsewhere.
Platform matrix
| Platform | Default path | Status |
|---|---|---|
| macOS arm64 | Native CPU | Optimized path and local transport expansion |
| Linux x86-64 | Native CPU | Optimized path |
| Linux arm64 | PyTorch | Reference path |
| CUDA or MPS device | PyTorch | Reference path |
See what your machine selected
shell
fermion info
fermion bench --tokens 64info names the active backend and explains why. Published throughput figures describe the native path. bench measures the exact path active on the current machine.
Pin or require a backend
shell
fermion chat --backend native
fermion generate "Hello" --backend torch --dtype float32--backend native fails rather than silently using a slower path. Use --native-bin or FERMION_NATIVE_BIN to select a specific runner.
Native thread settings
The native runner uses one fewer thread than the detected CPU count, capped at 16. Set FERMION_THREADS to choose a count, and raise the ceiling deliberately with FERMION_MAX_THREADS.
shell
FERMION_THREADS=12 fermion bench
FERMION_MAX_THREADS=24 FERMION_THREADS=24 fermion bench