> For the complete documentation index, see [llms.txt](https://carec.gitbook.io/carec-docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://carec.gitbook.io/carec-docs/documentation/simulation/performance-and-determinism.md).

# Performance and Determinism

A run can be logically correct yet misleading if sensor rates collapse or simulated time diverges. CAREC therefore reports timing and resource behavior with functional results.

## Metrics

| Metric                         | Why it matters                                   |
| ------------------------------ | ------------------------------------------------ |
| Real-time factor               | Shows whether physics keeps pace with wall time  |
| Physics step and update rate   | Controls dynamics and contact fidelity           |
| Topic frequency and jitter     | Detects starving sensors and control loops       |
| End-to-end command latency     | Bounds response from decision to simulated drive |
| CPU, GPU, and memory           | Supports contributor and CI capacity planning    |
| Dropped messages / queue depth | Exposes overload and QoS problems                |
| Run-to-run variance            | Detects hidden nondeterminism                    |

## Resource profiles

* **Core/headless:** reduced graphics, essential sensors, smoke and CI.
* **Developer desktop:** GUI, RViz, standard sensor set, interactive debugging.
* **High-fidelity:** dense sensors, actors, recording, perception and synthetic data.

Publish measured requirements only after benchmarking. Until then, avoid presenting a particular GPU, memory size, or frame rate as a guaranteed minimum.

## Determinism controls

Fix random seeds, start state, world version, update rates, executor configuration, parameters, and scenario event timing. Compare outcomes with tolerances appropriate to floating-point physics, not byte-for-byte logs.


---

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