improve bloom filter benchmark #78

benches/bloom.rs

@@ -2,7 +2,7 @@ use criterion::{criterion_group, criterion_main, Criterion};
 use lsm_tree::bloom::BloomFilter;
 
 fn filter_construction(c: &mut Criterion) {
-    let mut filter = BloomFilter::with_fp_rate(1_000_000, 0.001);
+    let mut filter = BloomFilter::with_fp_rate(1_000_000, 0.01);
 
     c.bench_function("bloom filter add key", |b| {
         b.iter(|| {
@@ -13,24 +13,48 @@ fn filter_construction(c: &mut Criterion) {
 }
 
 fn filter_contains(c: &mut Criterion) {
-    let mut filter = BloomFilter::with_fp_rate(10, 0.0001);
-
-    for key in [
-        b"item0", b"item1", b"item2", b"item3", b"item4", b"item5", b"item6", b"item7", b"item8",
-        b"item9",
-    ] {
-        filter.set_with_hash(BloomFilter::get_hash(key));
-
-        assert!(!filter.contains(nanoid::nanoid!().as_bytes()));
+    for fpr in [0.01, 0.001, 0.0001, 0.00001] {
+        let mut filter = BloomFilter::with_fp_rate(100_000, fpr);
+
+        for key in [
+            b"item0", b"item1", b"item2", b"item3", b"item4", b"item5", b"item6", b"item7",
+            b"item8", b"item9",
+        ] {
+            filter.set_with_hash(BloomFilter::get_hash(key));
+
+            assert!(!filter.contains(nanoid::nanoid!().as_bytes()));
+        }
+
+        c.bench_function(
+            &format!(
+                "bloom filter contains key, true positive ({}%)",
+                fpr * 100.0
+            ),
+            |b| {
+                b.iter(|| {
+                    // We hash once and then do 4 runs of bloom filter lookups
+                    // to simulate hash sharing (https://fjall-rs.github.io/post/bloom-filter-hash-sharing/)
+                    //  and L0 having 4 segments + 1 check in L1
+                    let hash = BloomFilter::get_hash(b"item4");
+
+                    for _ in 0..5 {
+                        assert!(filter.contains_hash(hash));
+                    }
+                });
+            },
+        );
+
+        /*
+        c.bench_function(
+            &format!(
+                "bloom filter contains key, true negative ({}%)",
+                fpr * 100.0
+            ),
+            |b| {
+                b.iter(|| filter.contains(b"sdfafdas"));
+            },
+        ); */
     }
-
-    c.bench_function("bloom filter contains key, true positive", |b| {
-        b.iter(|| filter.contains(b"item4"));
-    });
-
-    c.bench_function("bloom filter contains key, true negative", |b| {
-        b.iter(|| filter.contains(b"sdfafdas"));
-    });
 }
 
 criterion_group!(benches, filter_construction, filter_contains,);