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//! Gather named corpus rows into dense, normalized FP32 device storage.
use crate::*;
use hrx::{Event, View};
impl Corpus {
/// Gather insertion IDs into contiguous row-major FP32 device storage.
///
/// Output row `i` corresponds to `rows[i]`; arbitrary order and duplicates
/// are preserved. Each component is the stored FP16 value expanded to FP32
/// and multiplied by its stored inverse norm. Rows have exactly
/// [`Self::dimensions`] components, with no dimension or row padding.
/// This normalization permits cosine comparisons by dot product, subject
/// to FP32 rounding; pairwise dots need not be bitwise equal to search.
///
/// `output` must be four-byte aligned and cover `rows.len()*dimensions*4`
/// bytes. A larger binding's suffix is untouched. All IDs and extents are
/// checked before submission; invalid arguments leave output unchanged.
/// An empty request records an event without writing output. At most 2^30
/// gathered rows and 2^32 output components are supported; [`MAX_BATCH`] and
/// [`MAX_K`] do not restrict this operation.
///
/// The stream and output must belong to this corpus's device. Output may
/// not alias corpus storage. Callers must order prior output uses on this
/// stream, or wait on their events first. Returned completion can be waited
/// on by another stream; same-stream consumers may be queued immediately.
/// No vector readback or host completion wait occurs. First use compiles a
/// kernel cached across corpus clones; ID routing uses stream-owned scratch
/// that can be reused on subsequent calls. Runtime failures may leave partial
/// output and do not cancel commands already submitted.
///
/// ```no_run
/// # fn example(corpus: &hrxdb::Corpus) -> hrxdb::Result<()> {
/// let mut stream = corpus.stream()?;
/// let ids = [7, 2, 7];
/// let block = stream.allocate(ids.len() * corpus.dimensions() * 4)?;
/// let done = corpus.gather_into(&mut stream, &ids, block.binding())?;
/// // Bind block to a custom kernel here, or use it as DeviceQueries.
/// let mut consumer = corpus.stream()?;
/// consumer.wait_event(&done)?;
/// # Ok(())
/// # }
/// ```
pub fn gather_into(
&self,
stream: &mut Stream,
rows: &[u32],
output: View<'_>,
) -> Result<Event> {
if stream.device_id() != self.inner.device_id {
return Err(invalid("gather stream belongs to another device"));
}
let bytes = gather_bytes(rows.len(), self.dimensions())?;
if !output.offset().is_multiple_of(4) {
return Err(invalid("gather output must be four-byte aligned"));
}
let output = output.slice(0, bytes)?;
if rows.iter().any(|&id| id as usize >= self.len()) {
return Err(invalid("gather ID is outside the corpus"));
}
if rows.is_empty() {
return stream.record_event();
}
let shards = &self.inner.shards;
if shards.iter().any(|s| {
std::ptr::eq(output.owner(), &s.data) || std::ptr::eq(output.owner(), &s.norms)
}) {
return Err(invalid("gather output must not alias corpus storage"));
}
// Route only the requested IDs. Shader work is O(rows*dimensions), not
// O(corpus size) or O(rows*shards). Destinations restore requested order.
let mut routes = vec![Vec::<[u32; 2]>::new(); shards.len()];
for (destination, &id) in rows.iter().enumerate() {
let shard = shards.partition_point(|s| s.start <= id as usize) - 1;
routes[shard].push([
(id as usize - shards[shard].start) as u32,
destination as u32,
]);
}
let mut payload = Vec::with_capacity(rows.len() * 8);
for pair in routes.iter().flatten() {
payload.extend_from_slice(&pair[0].to_le_bytes());
payload.extend_from_slice(&pair[1].to_le_bytes());
}
let kernel = self.gather_kernel(stream)?;
let routing = stream.scratch(payload.len())?;
stream.upload(routing.try_slice(0, payload.len())?, &payload)?;
let mut offset = 0;
for (shard, requests) in shards.iter().zip(&routes) {
if requests.is_empty() {
continue;
}
let mut constants = Constants::new();
constants.push(requests.len() as u32)?;
constants.push(shard.count as u32)?;
constants.push(rows.len() as u32)?;
// SAFETY: CPU routing validates source IDs and assigns unique,
// in-bounds destinations. Specialized strides/limits match both
// buffers. Every requested component is written exactly once.
unsafe {
stream.dispatch(
&kernel,
[requests.len() as u32, 1, 1],
[128, 1, 1],
&constants,
&[
shard.data.binding(),
shard.norms.binding(),
routing.try_slice(offset, requests.len() * 8)?,
output,
],
)?;
}
offset += requests.len() * 8;
}
stream.recycle(routing)?;
stream.record_event()
}
fn gather_kernel(&self, stream: &Stream) -> Result<Kernel> {
let mut cached = self
.inner
.gather
.lock()
.map_err(|_| invalid("gather cache poisoned"))?;
if let Some(kernel) = &*cached {
return Ok(kernel.clone());
}
let compiler = hrx::loom::Compiler::with_options(
None,
hrx::loom::CompilerOptions {
target: stream.target().clone(),
..Default::default()
},
)?;
let mut spec = kernels::named_spec("gather");
for (key, value) in [
("gather.dimensions", self.dimensions()),
("gather.padded", self.padded_dimensions()),
(
"gather.input_limit",
(MAX_ELEMENTS / self.padded_dimensions()).min(MAX_ROWS),
),
(
"gather.output_limit",
(MAX_ELEMENTS / self.dimensions()).min(MAX_ROWS),
),
] {
spec.config.insert(key.into(), value.to_string());
}
let (kernel, _) = compile(
&compiler,
stream,
include_str!("../kernels/gather.loom"),
spec,
)?;
*cached = Some(kernel.clone());
Ok(kernel)
}
}
fn gather_bytes(rows: usize, dimensions: usize) -> Result<usize> {
let elements = rows.checked_mul(dimensions).filter(|&n| n <= MAX_ELEMENTS);
if rows > MAX_ROWS || elements.is_none() {
return Err(invalid("gather exceeds supported output extent"));
}
Ok(elements.unwrap() * 4)
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn output_extents_respect_element_address_limits() {
assert_eq!(gather_bytes(0, 3).unwrap(), 0);
for d in [1, 3, 384, 16_384] {
let rows = (MAX_ELEMENTS / d).min(MAX_ROWS);
assert_eq!(gather_bytes(rows, d).unwrap(), rows * d * 4);
assert!(gather_bytes(rows + 1, d).is_err());
}
assert!(gather_bytes(usize::MAX, 16_384).is_err());
}
}