osmarks/meme-search-engine
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fix overflow bug

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osmarks 2025-01-01 14:40:00 +00:00
parent e0cf65204b
commit 35df1201e2
2 changed files with 14 additions and 8 deletions
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3
diskann/src/main.rs
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@ -7,7 +7,7 @@ use std::{io::Read, time::Instant};
use anyhow::Result;
use half::f16;
use diskann::{build_graph, IndexBuildConfig, medioid, IndexGraph, greedy_search, Scratch, vector::{fast_dot, dot, VectorList, self}, Timer};
use diskann::{build_graph, IndexBuildConfig, medioid, IndexGraph, greedy_search, Scratch, vector::{fast_dot, SCALE, dot, VectorList, self}, Timer};
use simsimd::SpatialSimilarity;
const D_EMB: usize = 1152;
@ -40,6 +40,7 @@ fn main() -> Result<()> {
}
let pq_scores = codec.asymmetric_dot_product(&query, &codes);
for (x, y) in real_scores.iter().zip(pq_scores.iter()) {
let y = (*y as f32) / SCALE;
println!("{} {} {} {}", x, y, x - y, (x - y) / x);
}
}

19
diskann/src/vector.rs
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@ -4,7 +4,6 @@ use half::f16;
use simsimd::SpatialSimilarity;
use fastrand::Rng;
use serde::{Serialize, Deserialize};
use tracing_subscriber::field::RecordFields;
#[derive(Debug, Clone)]
pub struct Vector(Vec<f16>);
@ -46,12 +45,12 @@ impl Vector {
}
// Floats are vaguely annoying and not sortable (trivially), so we mostly represent dot products as integers
const SCALE: f32 = 281474976710656.0;
const SCALE_F64: f64 = SCALE as f64;
pub const SCALE: f32 = 1099511627776.0;
pub const SCALE_F64: f64 = SCALE as f64;
pub fn dot<'a>(x: VectorRef<'a>, y: VectorRef<'a>) -> f32 {
pub fn dot<'a>(x: VectorRef<'a>, y: VectorRef<'a>) -> i64 {
// safety is not real
(simsimd::f16::dot(unsafe { std::mem::transmute(x) }, unsafe { std::mem::transmute(y) }).unwrap()) as f32
scale_dot_result_f64(simsimd::f16::dot(unsafe { std::mem::transmute(x) }, unsafe { std::mem::transmute(y) }).unwrap())
}
pub fn to_svector(vec: VectorRef) -> SVector {
@ -404,11 +403,17 @@ impl ProductQuantizer {
// I have no idea why but we somehow have significant degradation in search quality
// if this accumulates in integers. As such, do floats and convert at the end.
// I'm sure there are fascinating reasons for this, but God is dead, God remains dead, etc.
scores.into_iter().map(|x| (x * SCALE) as i64).collect()
scores.into_iter().map(scale_dot_result).collect()
}
}
pub fn scale_dot_result(x: f64) -> i64 {
#[inline]
pub fn scale_dot_result(x: f32) -> i64 {
(x * SCALE) as i64
}
#[inline]
pub fn scale_dot_result_f64(x: f64) -> i64 {
(x * SCALE_F64) as i64
}