sim-lib-compute-wgpu 0.1.0

//! Portable GPU adapter discovery and raw probe evidence.

use std::sync::mpsc;

use wgpu::{
    Adapter, Backends, BufferDescriptor, BufferUsages, DeviceDescriptor, ExperimentalFeatures,
    Features, Instance, Limits, MapMode, MemoryHints, PollType,
};

/// Requested limits and optional features passed to `wgpu`.
#[derive(Clone, Debug, PartialEq, Eq)]
pub struct RequestedWgpuProfile {
    /// Requested device limits.
    pub limits: WgpuLimitEvidence,
    /// Whether timestamp queries were requested.
    pub timestamp_query: bool,
    /// Whether shader f16 was requested.
    pub shader_f16: bool,
}

impl RequestedWgpuProfile {
    fn from_parts(limits: Limits, features: Features) -> Self {
        Self {
            limits: WgpuLimitEvidence::from_limits(&limits),
            timestamp_query: features.contains(Features::TIMESTAMP_QUERY),
            shader_f16: features.contains(Features::SHADER_F16),
        }
    }
}

/// Limits recorded from either the requested or granted device contract.
#[derive(Clone, Debug, PartialEq, Eq)]
pub struct WgpuLimitEvidence {
    /// Maximum buffer size.
    pub max_buffer_size: u64,
    /// Maximum storage buffer binding size.
    pub max_storage_buffer_binding_size: u64,
    /// Maximum uniform buffer binding size.
    pub max_uniform_buffer_binding_size: u64,
    /// Minimum storage buffer offset alignment.
    pub min_storage_buffer_offset_alignment: u32,
    /// Minimum uniform buffer offset alignment.
    pub min_uniform_buffer_offset_alignment: u32,
    /// Maximum compute workgroups per dimension.
    pub max_compute_workgroups_per_dimension: u32,
    /// Maximum compute invocations per workgroup.
    pub max_compute_invocations_per_workgroup: u32,
    /// Maximum compute workgroup size x.
    pub max_compute_workgroup_size_x: u32,
    /// Maximum compute workgroup size y.
    pub max_compute_workgroup_size_y: u32,
    /// Maximum compute workgroup size z.
    pub max_compute_workgroup_size_z: u32,
}

impl WgpuLimitEvidence {
    fn from_limits(limits: &Limits) -> Self {
        Self {
            max_buffer_size: limits.max_buffer_size,
            max_storage_buffer_binding_size: limits.max_storage_buffer_binding_size,
            max_uniform_buffer_binding_size: limits.max_uniform_buffer_binding_size,
            min_storage_buffer_offset_alignment: limits.min_storage_buffer_offset_alignment,
            min_uniform_buffer_offset_alignment: limits.min_uniform_buffer_offset_alignment,
            max_compute_workgroups_per_dimension: limits.max_compute_workgroups_per_dimension,
            max_compute_invocations_per_workgroup: limits.max_compute_invocations_per_workgroup,
            max_compute_workgroup_size_x: limits.max_compute_workgroup_size_x,
            max_compute_workgroup_size_y: limits.max_compute_workgroup_size_y,
            max_compute_workgroup_size_z: limits.max_compute_workgroup_size_z,
        }
    }
}

/// Feature evidence recorded from a granted device.
#[derive(Clone, Debug, PartialEq, Eq)]
pub struct WgpuCapabilityEvidence {
    /// Whether timestamp queries are granted.
    pub timestamp_query: bool,
    /// Whether shader f16 is granted.
    pub shader_f16: bool,
    /// Whether primary buffers may be mapped.
    pub mappable_primary_buffers: bool,
}

impl WgpuCapabilityEvidence {
    fn from_features(features: Features) -> Self {
        Self {
            timestamp_query: features.contains(Features::TIMESTAMP_QUERY),
            shader_f16: features.contains(Features::SHADER_F16),
            mappable_primary_buffers: features.contains(Features::MAPPABLE_PRIMARY_BUFFERS),
        }
    }
}

/// Adapter identity and requested/granted capability evidence.
#[derive(Clone, Debug, PartialEq, Eq)]
pub struct WgpuAdapterEvidence {
    /// Deterministic ordinal assigned after sorting adapters.
    pub ordinal: usize,
    /// Diagnostic adapter name from `wgpu`.
    pub name: String,
    /// Diagnostic backend label from `wgpu`.
    pub backend: String,
    /// Diagnostic adapter type from `wgpu`.
    pub adapter_type: String,
    /// Diagnostic vendor id.
    pub vendor: u32,
    /// Diagnostic device id.
    pub device: u32,
    /// Requested profile.
    pub requested: RequestedWgpuProfile,
    /// Granted device limits.
    pub granted_limits: WgpuLimitEvidence,
    /// Granted features.
    pub granted_features: WgpuCapabilityEvidence,
}

impl WgpuAdapterEvidence {
    /// Sort key that keeps enumeration deterministic without treating identity
    /// as product logic.
    pub fn sort_key(&self) -> (&str, &str, &str, u32, u32) {
        (
            self.backend.as_str(),
            self.adapter_type.as_str(),
            self.name.as_str(),
            self.vendor,
            self.device,
        )
    }
}

/// Transfer and mapping probe evidence.
#[derive(Clone, Debug, PartialEq, Eq)]
pub struct TransferEvidence {
    /// Bytes written and read back.
    pub bytes: u64,
    /// Whether queue write plus copy completed.
    pub transfer_ok: bool,
    /// Whether map-read completed and matched the payload.
    pub mapping_ok: bool,
}

/// One bounded allocation attempt.
#[derive(Clone, Debug, PartialEq, Eq)]
pub struct AllocationAttempt {
    /// Attempted byte size.
    pub bytes: u64,
    /// Whether creating the buffer succeeded.
    pub success: bool,
}

/// Probe evidence required before a site is exported.
#[derive(Clone, Debug, PartialEq, Eq)]
pub struct ProbeEvidence {
    /// Transfer and mapping evidence.
    pub transfer: TransferEvidence,
    /// Bounded allocation attempts.
    pub allocation_attempts: Vec<AllocationAttempt>,
}

impl ProbeEvidence {
    /// Returns true when all required probes succeeded.
    pub fn successful(&self) -> bool {
        self.transfer.transfer_ok
            && self.transfer.mapping_ok
            && self
                .allocation_attempts
                .iter()
                .any(|attempt| attempt.success && attempt.bytes > 0)
    }
}

/// One successful adapter probe.
#[derive(Clone, Debug, PartialEq, Eq)]
pub struct WgpuAdapterProbe {
    /// Adapter and capability evidence.
    pub adapter: WgpuAdapterEvidence,
    /// Raw probe evidence.
    pub probe: ProbeEvidence,
}

/// Complete discovery result.
#[derive(Clone, Debug, Default, PartialEq, Eq)]
pub struct WgpuDiscovery {
    /// Successful adapter probes, in deterministic order.
    pub adapters: Vec<WgpuAdapterProbe>,
    /// Diagnostic errors from adapters that did not become sites.
    pub diagnostics: Vec<String>,
}

impl WgpuDiscovery {
    /// Builds a discovery result and drops unsuccessful adapters from the site
    /// list while preserving their diagnostics.
    pub fn from_probes(probes: Vec<WgpuAdapterProbe>, mut diagnostics: Vec<String>) -> Self {
        let mut adapters = Vec::new();
        for probe in probes {
            if probe.probe.successful() {
                adapters.push(probe);
            } else {
                diagnostics.push(format!(
                    "wgpu adapter {} did not pass required probes",
                    probe.adapter.name
                ));
            }
        }
        adapters.sort_by(|left, right| left.adapter.sort_key().cmp(&right.adapter.sort_key()));
        for (ordinal, probe) in adapters.iter_mut().enumerate() {
            probe.adapter.ordinal = ordinal;
        }
        Self {
            adapters,
            diagnostics,
        }
    }
}

/// Bounded probe policy.
#[derive(Clone, Debug, PartialEq, Eq)]
pub struct ProbePolicy {
    /// Backends to enumerate.
    pub backends: Backends,
    /// Bytes used by the transfer and map probe.
    pub transfer_bytes: u64,
    /// Largest allocation attempt, capped again by granted limits.
    pub max_allocation_probe_bytes: u64,
}

impl Default for ProbePolicy {
    fn default() -> Self {
        Self {
            backends: Backends::all(),
            transfer_bytes: 16,
            max_allocation_probe_bytes: 16 * 1024 * 1024,
        }
    }
}

/// Discovery failure for infrastructure-level probe setup.
#[derive(Clone, Debug, PartialEq, Eq)]
pub struct WgpuDiscoveryError {
    message: String,
}

impl WgpuDiscoveryError {
    fn new(message: impl Into<String>) -> Self {
        Self {
            message: message.into(),
        }
    }
}

impl std::fmt::Display for WgpuDiscoveryError {
    fn fmt(&self, formatter: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        formatter.write_str(&self.message)
    }
}

impl std::error::Error for WgpuDiscoveryError {}

/// Enumerates adapters and returns only probe-backed site candidates.
pub fn discover_wgpu_adapters(policy: &ProbePolicy) -> Result<WgpuDiscovery, WgpuDiscoveryError> {
    let instance = Instance::default();
    let adapters = pollster::block_on(instance.enumerate_adapters(policy.backends));
    let mut probes = Vec::new();
    let mut diagnostics = Vec::new();

    for adapter in adapters {
        match probe_adapter(adapter, policy) {
            Ok(probe) => probes.push(probe),
            Err(error) => diagnostics.push(error.to_string()),
        }
    }

    Ok(WgpuDiscovery::from_probes(probes, diagnostics))
}

fn probe_adapter(
    adapter: Adapter,
    policy: &ProbePolicy,
) -> Result<WgpuAdapterProbe, WgpuDiscoveryError> {
    let info = adapter.get_info();
    let supported_features = adapter.features();
    let required_features = supported_features & (Features::TIMESTAMP_QUERY | Features::SHADER_F16);
    let required_limits = Limits::downlevel_defaults().using_resolution(adapter.limits());
    let requested = RequestedWgpuProfile::from_parts(required_limits.clone(), required_features);
    let descriptor = DeviceDescriptor {
        label: Some("sim-compute-wgpu-probe"),
        required_features,
        required_limits,
        experimental_features: ExperimentalFeatures::disabled(),
        memory_hints: MemoryHints::Performance,
        trace: Default::default(),
    };
    let (device, queue) = pollster::block_on(adapter.request_device(&descriptor))
        .map_err(|err| WgpuDiscoveryError::new(format!("wgpu request_device failed: {err}")))?;

    let transfer = probe_transfer(&device, &queue, policy.transfer_bytes)?;
    let allocation_attempts = probe_allocations(
        &device,
        device
            .limits()
            .max_buffer_size
            .min(policy.max_allocation_probe_bytes),
    );

    Ok(WgpuAdapterProbe {
        adapter: WgpuAdapterEvidence {
            ordinal: 0,
            name: info.name,
            backend: format!("{:?}", info.backend),
            adapter_type: format!("{:?}", info.device_type),
            vendor: info.vendor,
            device: info.device,
            requested,
            granted_limits: WgpuLimitEvidence::from_limits(&device.limits()),
            granted_features: WgpuCapabilityEvidence::from_features(device.features()),
        },
        probe: ProbeEvidence {
            transfer,
            allocation_attempts,
        },
    })
}

fn probe_transfer(
    device: &wgpu::Device,
    queue: &wgpu::Queue,
    bytes: u64,
) -> Result<TransferEvidence, WgpuDiscoveryError> {
    let bytes = bytes.max(4).next_multiple_of(4);
    let payload = (0..bytes).map(|idx| (idx % 251) as u8).collect::<Vec<_>>();
    let source = device.create_buffer(&BufferDescriptor {
        label: Some("sim-compute-wgpu-transfer-source"),
        size: bytes,
        usage: BufferUsages::COPY_SRC | BufferUsages::COPY_DST,
        mapped_at_creation: false,
    });
    let readback = device.create_buffer(&BufferDescriptor {
        label: Some("sim-compute-wgpu-transfer-readback"),
        size: bytes,
        usage: BufferUsages::COPY_DST | BufferUsages::MAP_READ,
        mapped_at_creation: false,
    });
    queue.write_buffer(&source, 0, &payload);
    let mut encoder = device.create_command_encoder(&wgpu::CommandEncoderDescriptor {
        label: Some("sim-compute-wgpu-transfer-encoder"),
    });
    encoder.copy_buffer_to_buffer(&source, 0, &readback, 0, bytes);
    queue.submit([encoder.finish()]);

    let (sender, receiver) = mpsc::channel();
    readback.slice(..).map_async(MapMode::Read, move |result| {
        let _ = sender.send(result);
    });
    device
        .poll(PollType::wait_indefinitely())
        .map_err(|err| WgpuDiscoveryError::new(format!("wgpu poll failed: {err}")))?;
    receiver
        .recv()
        .map_err(|err| WgpuDiscoveryError::new(format!("wgpu map callback failed: {err}")))?
        .map_err(|err| WgpuDiscoveryError::new(format!("wgpu map failed: {err}")))?;

    let mapped = readback
        .slice(..)
        .get_mapped_range()
        .map_err(|err| WgpuDiscoveryError::new(format!("wgpu mapped range failed: {err}")))?
        .to_vec();
    readback.unmap();
    Ok(TransferEvidence {
        bytes,
        transfer_ok: true,
        mapping_ok: mapped == payload,
    })
}

fn probe_allocations(device: &wgpu::Device, ceiling: u64) -> Vec<AllocationAttempt> {
    [4096, 1024 * 1024, ceiling]
        .into_iter()
        .filter(|bytes| *bytes > 0)
        .map(|bytes| {
            let buffer = device.create_buffer(&BufferDescriptor {
                label: Some("sim-compute-wgpu-allocation-probe"),
                size: bytes,
                usage: BufferUsages::COPY_DST,
                mapped_at_creation: false,
            });
            drop(buffer);
            AllocationAttempt {
                bytes,
                success: true,
            }
        })
        .collect()
}