# bellperson [![Crates.io](https://img.shields.io/crates/v/bellperson.svg)](https://crates.io/crates/bellperson)

> This is a fork of the great [bellman](https://github.com/zkcrypto/bellman) library.

`bellman` is a crate for building zk-SNARK circuits. It provides circuit traits
and primitive structures, as well as basic gadget implementations such as
booleans and number abstractions.

## GPU

This fork contains GPU parallel acceleration to the FFT and Multiexponentation algorithms in the groth16 prover codebase under a conditional compilation feature `#[cfg(feature = "gpu")]` and `gpu-test` for testing.

### Requirements
- NVIDIA GPU Graphics Driver

- OpenCL

### Environment variables

The gpu extension contains some env vars that may be set externally to this library.

`BELLMAN_NO_GPU`

Will disable the GPU feature from the library and force usage of the CPU.
```
Example
env::set_var("BELLMAN_NO_GPU", "1");
```

`BELLMAN_CUSTOM_GPU`

Will allow for adding a GPU not in the tested list. This requires researching the name of the GPU device and the number of cores in the format `["name:cores"]`.
```
Example
env::set_var("BELLMAN_CUSTOM_GPU", "GeForce RTX 2080 Ti:4352, GeForce GTX 1060:1280");
```

`BELLMAN_CPU_UTILIZATION`

Can be set in the interval [0,1] to designate a proportion of the multiexponenation calculation to be moved to cpu in parallel to the GPU to keep all hardware occupied.

```
Example
env::set_var("BELLMAN_CPU_UTILIZATION", "0.5");
```

#### Supported / Tested Cards

Currently only Nvidia hardware is supported, see [issue](https://github.com/finalitylabs/bellman/issues/3). Depending on the size of the proof being passed to the gpu for work, certain cards will not be able to allocate enough memory to either the FFT or Multiexp kernel. Below are a list of devices that work for small sets. In the future we will add the cuttoff point at which a given card will not be able to allocate enough memory to utilize the GPU.

```
("Device_Name", Cores),
("TITAN RTX", 4608),
("Tesla V100", 5120),
("Tesla P100", 3584),
("Tesla T4", 2560),
("GeForce RTX 2080 Ti", 4352),
("GeForce RTX 2080 SUPER", 3072),
("GeForce RTX 2080", 2944),
("GeForce RTX 2070 SUPER", 2560),
("GeForce GTX 1080 Ti", 3584),
("GeForce GTX 1080", 2560),
("GeForce GTX 2060", 1920),
("GeForce GTX 1660 Ti", 1536),
("GeForce GTX 1060", 1280),
("GeForce GTX 1650 SUPER", 1280),
("GeForce GTX 1650", 896),
```

## License

Licensed under either of

 * Apache License, Version 2.0, ([LICENSE-APACHE](LICENSE-APACHE) or
   http://www.apache.org/licenses/LICENSE-2.0)
 * MIT license ([LICENSE-MIT](LICENSE-MIT) or http://opensource.org/licenses/MIT)

at your option.

### Contribution

Unless you explicitly state otherwise, any contribution intentionally
submitted for inclusion in the work by you, as defined in the Apache-2.0
license, shall be dual licensed as above, without any additional terms or
conditions.
