57 lines
1.7 KiB
Rust
57 lines
1.7 KiB
Rust
use std::cmp::Ordering;
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use crate::{RawDocument, MResult};
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use super::{Criterion, Context, ContextMut, prepare_query_distances};
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pub struct Typo;
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impl Criterion for Typo {
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fn name(&self) -> &str { "typo" }
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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_query_distances(documents, ctx.query_mapping, ctx.postings_lists);
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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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// This function is a wrong logarithmic 10 function.
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// It is safe to panic on input number higher than 3,
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// the number of typos is never bigger than that.
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#[inline]
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#[allow(clippy::approx_constant)]
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fn custom_log10(n: u8) -> f32 {
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match n {
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0 => 0.0, // log(1)
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1 => 0.30102, // log(2)
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2 => 0.47712, // log(3)
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3 => 0.60205, // log(4)
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_ => panic!("invalid number"),
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}
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}
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#[inline]
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fn compute_typos(distances: &[Option<u8>]) -> usize {
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let mut number_words: usize = 0;
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let mut sum_typos = 0.0;
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for distance in distances {
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if let Some(distance) = distance {
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sum_typos += custom_log10(*distance);
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number_words += 1;
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}
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}
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(number_words as f32 / (sum_typos + 1.0) * 1000.0) as usize
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}
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let lhs = compute_typos(&lhs.processed_distances);
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let rhs = compute_typos(&rhs.processed_distances);
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lhs.cmp(&rhs).reverse()
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}
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}
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