# Get an example running.

> Resolve common toolchain, backend, parameter, and documentation issues.

- Canonical page: https://www.poulpy.dev/docs/troubleshooting/
- Poulpy version: 0.9.0
- Source revision: [`7dd13e6aa9808982f5355fb6acb70ca434de4e35`](https://github.com/poulpy-fhe/poulpy/tree/7dd13e6aa9808982f5355fb6acb70ca434de4e35)
- Documentation reviewed: 2026-10-08
- Audience: For application developers

## Build and toolchain problems

| Symptom | Check | Next action |
| --- | --- | --- |
| Missing compiler, linker, or native headers | Git, rustup, and native build tools are installed | Follow the platform prerequisites in [Quickstart](https://www.poulpy.dev/docs/quickstart/#1-get-the-source); include the first compiler error when asking for help |
| An unstable Rust feature is unavailable | The command is running under the pinned nightly | Run from the checkout or downloaded example directory so rustup reads `rust-toolchain.toml` |
| Cargo wants to change the lockfile | Manifest and lockfile come from the same revision | Restore a matching download or checkout; do not remove `--locked` to hide a version mismatch |
| A guide names a missing type | Source and published versions differ | Check [Versions](https://www.poulpy.dev/docs/versions/) and generate local rustdoc |

## Backend problems

Backend requirements depend on the target hardware. For the x86 CPU backends, enable both the Cargo feature and the required CPU instructions. Read [Backends](https://www.poulpy.dev/docs/backends/) for the exact combination. Start with the portable backend to separate application problems from hardware configuration. For reproducible performance measurements, compile in release mode and record the flags.

## Incorrect results or parameter errors

Check the input range, slot count, encoding scale, destination width, and required evaluation keys. Record the metadata before and after each operation. A negative or exhausted budget, mismatched key shape, or insufficient accumulator capacity needs a parameter or circuit correction.

The [parameter guide](https://www.poulpy.dev/docs/parameters/) explains what to record. Increasing a modulus to fix correctness also changes the security analysis; review the full configuration.

## A useful bug report

Include the source revision, Rust version, OS, hardware and relevant device runtime/driver versions, backend and feature flags, exact command, first error, and a minimal public reproducer. Use synthetic inputs and newly generated test keys rather than application secrets. Report vulnerabilities through the private contact on [Security](https://www.poulpy.dev/docs/security/); use [GitHub issues](https://github.com/poulpy-fhe/poulpy/issues) for ordinary questions.