wgpu/examples/hello-compute/main.rs

use std::{convert::TryInto as _, str::FromStr};
use zerocopy::AsBytes as _;

async fn run() {
    env_logger::init();

    // For now this just panics if you didn't pass numbers. Could add proper error handling.
    if std::env::args().len() == 1 {
        panic!("You must pass a list of positive integers!")
    }
    let numbers: Vec<u32> = std::env::args()
        .skip(1)
        .map(|s| u32::from_str(&s).expect("You must pass a list of positive integers!"))
        .collect();

    let slice_size = numbers.len() * std::mem::size_of::<u32>();
    let size = slice_size as wgpu::BufferAddress;

    let adapter = wgpu::Adapter::request(
        &wgpu::RequestAdapterOptions {
            power_preference: wgpu::PowerPreference::Default,
        },
        wgpu::BackendBit::PRIMARY,
    )
    .unwrap();

    let (device, mut queue) = adapter.request_device(&wgpu::DeviceDescriptor {
        extensions: wgpu::Extensions {
            anisotropic_filtering: false,
        },
        limits: wgpu::Limits::default(),
    });

    let cs = include_bytes!("shader.comp.spv");
    let cs_module =
        device.create_shader_module(&wgpu::read_spirv(std::io::Cursor::new(&cs[..])).unwrap());

    let staging_buffer = device.create_buffer_with_data(
        numbers.as_slice().as_bytes(),
        wgpu::BufferUsage::MAP_READ | wgpu::BufferUsage::COPY_DST | wgpu::BufferUsage::COPY_SRC,
    );

    let storage_buffer = device.create_buffer(&wgpu::BufferDescriptor {
        size,
        usage: wgpu::BufferUsage::STORAGE
            | wgpu::BufferUsage::COPY_DST
            | wgpu::BufferUsage::COPY_SRC,
    });

    let bind_group_layout = device.create_bind_group_layout(&wgpu::BindGroupLayoutDescriptor {
        bindings: &[wgpu::BindGroupLayoutBinding {
            binding: 0,
            visibility: wgpu::ShaderStage::COMPUTE,
            ty: wgpu::BindingType::StorageBuffer {
                dynamic: false,
                readonly: false,
            },
        }],
    });

    let bind_group = device.create_bind_group(&wgpu::BindGroupDescriptor {
        layout: &bind_group_layout,
        bindings: &[wgpu::Binding {
            binding: 0,
            resource: wgpu::BindingResource::Buffer {
                buffer: &storage_buffer,
                range: 0 .. size,
            },
        }],
    });

    let pipeline_layout = device.create_pipeline_layout(&wgpu::PipelineLayoutDescriptor {
        bind_group_layouts: &[&bind_group_layout],
    });

    let compute_pipeline = device.create_compute_pipeline(&wgpu::ComputePipelineDescriptor {
        layout: &pipeline_layout,
        compute_stage: wgpu::ProgrammableStageDescriptor {
            module: &cs_module,
            entry_point: "main",
        },
    });

    let mut encoder = device.create_command_encoder(&wgpu::CommandEncoderDescriptor { todo: 0 });
    encoder.copy_buffer_to_buffer(&staging_buffer, 0, &storage_buffer, 0, size);
    {
        let mut cpass = encoder.begin_compute_pass();
        cpass.set_pipeline(&compute_pipeline);
        cpass.set_bind_group(0, &bind_group, &[]);
        cpass.dispatch(numbers.len() as u32, 1, 1);
    }
    encoder.copy_buffer_to_buffer(&storage_buffer, 0, &staging_buffer, 0, size);

    queue.submit(&[encoder.finish()]);

    if let Ok(mapping) = staging_buffer.map_read(0u64, size).await {
        let times : Box<[u32]> = mapping
            .as_slice()
            .chunks_exact(4)
            .map(|b| u32::from_ne_bytes(b.try_into().unwrap()))
            .collect();

        println!("Times: {:?}", times);
    }
}

fn main() {
    futures::executor::block_on(run());
}