# pimsim-nn Oracle Invariant

`backend-simulators/pim/pimsim-nn` is the performance oracle. Its simulation
behavior defines the hardware model used for Raptor/PIMCOMP comparisons.

## Required invariant

- Do not add instruction or operator support to pimsim-nn.
- Changes to pimsim-nn must preserve simulation behavior exactly. Acceptable
  changes are limited to behavior-neutral maintenance proven not to alter
  simulated timing, scheduling, power, energy, or supported input programs.
- Unsupported pimsim-nn operations must remain unsupported; do not approximate
  their timing or map them onto another operation.
- Adapt compiler inputs to the oracle instead. For YOLO, use
  `validation/networks/pimcomp_models/yolo11n/yolo11n-pimsim-nn.onnx`, the
  dedicated pimsim-ready performance artifact with Softmax operations removed.
  Use `validation/networks/yolo11n/depth_51/yolo11n_depth_51.onnx` for YOLO
  functional validation; removing Softmax changes the model's numerical
  behavior, so the pimsim-ready artifact is not a correctness reference.

Any proposed pimsim-nn behavior change requires explicit user authorization and
must not be introduced as part of a compiler optimization.