# Using AMD GPUs
## Prerequisites
- [Install ROCm 3.5](https://rocmdocs.amd.com/en/latest/Installation_Guide/Installation-Guide.html#supported-operating-systems)
## Running tests
The environment variable `BELLMAN_PLATFORM` determines which backend will be used.
To use the AMD backend, you can do something like:
```bash
export BELLMAN_PLATFORM="AMD Accelerated Parallel Processing"
RUST_LOG=info cargo test --features gpu -- --exact multiexp::gpu_multiexp_consistency --nocapture
```
## Notes
- We had trouble in Ubuntu 20.04 when running a single computer with both NVIDIA and AMD cards.
- The initial kernel compilation may take > 60sec at start up. This is not a problem afterwards. A possible mitigation would be to add kernel binary caching in the ocl-fil crate.