69 lines
2.1 KiB
Rust
69 lines
2.1 KiB
Rust
use std::cmp::{self, Ordering};
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use slice_group_by::GroupBy;
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use crate::bucket_sort::{SimpleMatch};
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use crate::{RawDocument, MResult};
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use super::{Criterion, Context, ContextMut, prepare_bare_matches};
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const MAX_DISTANCE: u16 = 8;
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pub struct Proximity;
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impl Criterion for Proximity {
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fn name(&self) -> &str { "proximity" }
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fn prepare<'h, 'p, 'tag, 'txn, 'q, 'r>(
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&self,
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ctx: ContextMut<'h, 'p, 'tag, 'txn, 'q>,
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documents: &mut [RawDocument<'r, 'tag>],
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) -> MResult<()>
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{
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prepare_bare_matches(documents, ctx.postings_lists, ctx.query_mapping);
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Ok(())
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}
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fn evaluate(&self, _ctx: &Context, lhs: &RawDocument, rhs: &RawDocument) -> Ordering {
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fn index_proximity(lhs: u16, rhs: u16) -> u16 {
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if lhs < rhs {
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cmp::min(rhs - lhs, MAX_DISTANCE)
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} else {
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cmp::min(lhs - rhs, MAX_DISTANCE) + 1
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}
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}
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fn attribute_proximity(lhs: SimpleMatch, rhs: SimpleMatch) -> u16 {
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if lhs.attribute != rhs.attribute { MAX_DISTANCE }
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else { index_proximity(lhs.word_index, rhs.word_index) }
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}
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fn min_proximity(lhs: &[SimpleMatch], rhs: &[SimpleMatch]) -> u16 {
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let mut min_prox = u16::max_value();
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for a in lhs {
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for b in rhs {
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let prox = attribute_proximity(*a, *b);
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min_prox = cmp::min(min_prox, prox);
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}
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}
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min_prox
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}
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fn matches_proximity(matches: &[SimpleMatch],) -> u16 {
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let mut proximity = 0;
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let mut iter = matches.linear_group_by_key(|m| m.query_index);
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// iterate over groups by windows of size 2
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let mut last = iter.next();
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while let (Some(lhs), Some(rhs)) = (last, iter.next()) {
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proximity += min_proximity(lhs, rhs);
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last = Some(rhs);
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}
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proximity
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}
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let lhs = matches_proximity(&lhs.processed_matches);
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let rhs = matches_proximity(&rhs.processed_matches);
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lhs.cmp(&rhs)
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}
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}
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