From 4d7001d70423e0c8470f40a08a103f0c2c6dd1cb Mon Sep 17 00:00:00 2001
From: Ariel Shtul <ashtul@gmail.com>
Date: Sat, 24 Aug 2024 18:40:38 +0300
Subject: [PATCH 1/3] add benchmarks

---
 benches/bench.rs | 82 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 82 insertions(+)
 create mode 100644 benches/bench.rs

diff --git a/benches/bench.rs b/benches/bench.rs
new file mode 100644
index 0000000..bae0983
--- /dev/null
+++ b/benches/bench.rs
@@ -0,0 +1,82 @@
+#![feature(test)]
+
+extern crate test;
+
+use bloomfilter::Bloom;
+
+/* Set benchmarks */
+
+fn inner_insert_bench(b: &mut test::Bencher, bitmap_size: usize, items_count: usize) {
+    let mut bf: Bloom<usize> = Bloom::new(bitmap_size / 8, items_count);
+    let mut index = items_count;
+    b.iter(|| {
+        index += 1;
+        test::black_box(bf.set(&index));
+    });
+}
+
+#[bench]
+#[inline(always)]
+fn bench_insert_100(b: &mut test::Bencher) {
+    inner_insert_bench(b, 1000, 100);
+}
+
+
+#[bench]
+#[inline(always)]
+fn bench_insert_1000(b: &mut test::Bencher) {
+    inner_insert_bench(b, 10000, 1000);
+}
+
+#[bench]
+#[inline(always)]
+fn bench_insert_m_1(b: &mut test::Bencher) {
+    inner_insert_bench(b, 10_000_000, 1_000_000);
+}
+
+#[bench]
+#[inline(always)]
+fn bench_insert_m_10(b: &mut test::Bencher) {
+    inner_insert_bench(b, 100_000_000, 10_000_000);
+}
+
+/* Get benchmarks */
+
+fn inner_get_bench(b: &mut test::Bencher, bitmap_size: usize, items_count: usize) {
+    let mut bf: Bloom<usize> = Bloom::new(bitmap_size / 8, items_count);
+    for index in 0..items_count {
+        bf.set(&index);
+    }
+    let mut index = items_count;
+    b.iter(|| {
+        index += 1;
+        test::black_box(bf.check(&index));
+    });
+}
+
+
+#[bench]
+#[inline(always)]
+fn bench_get_100(b: &mut test::Bencher) {
+    inner_get_bench(b, 1000, 100);
+}
+
+
+#[bench]
+#[inline(always)]
+fn bench_get_1000(b: &mut test::Bencher) {
+    inner_get_bench(b, 10000, 1000);
+}
+
+
+#[bench]
+#[inline(always)]
+fn bench_get_m_1(b: &mut test::Bencher) {
+    inner_get_bench(b, 10_000_000, 1_000_000);
+}
+
+#[bench]
+#[inline(always)]
+fn bench_get_m_10(b: &mut test::Bencher) {
+    inner_get_bench(b, 100_000_000, 10_000_000);
+}

From 6befceb73b0d0552c15178e747439dee92f13b97 Mon Sep 17 00:00:00 2001
From: Ariel Shtul <ashtul@gmail.com>
Date: Sat, 24 Aug 2024 19:14:02 +0300
Subject: [PATCH 2/3] add false positive test

---
 tests/bloom.rs | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/tests/bloom.rs b/tests/bloom.rs
index a997676..3533a24 100644
--- a/tests/bloom.rs
+++ b/tests/bloom.rs
@@ -50,3 +50,24 @@ fn bloom_test_load() {
     );
     assert!(cloned.check(&k));
 }
+
+/// Test the false positive rate of the bloom filter
+/// to ensure that using floor doesn't affect false positive rate
+/// in a significant way
+#[test]
+fn test_false_positive_rate() {
+    let capacities = [100, 1000, 10000, 100000, 1000000];
+    for capacity in capacities.iter() {
+        let mut bf: Bloom<usize> = Bloom::new(*capacity * 10 / 8, *capacity);
+        for index in 0..*capacity {
+            bf.set(&index);
+        }
+        let mut false_positives_count = 0.0;
+        for index in *capacity..11 * *capacity {
+            if bf.check(&index) {
+                false_positives_count += 1.0;
+            }
+        }
+        println!("False positive rate for capacity {}: {}", *capacity, false_positives_count / (10.0 * *capacity as f64));
+    }
+}
\ No newline at end of file

From 3230729041227dfc7f9a795d46e47004601079d2 Mon Sep 17 00:00:00 2001
From: Ariel Shtul <ashtul@gmail.com>
Date: Sat, 24 Aug 2024 19:24:56 +0300
Subject: [PATCH 3/3] always floor your bloom

---
 src/lib.rs | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/lib.rs b/src/lib.rs
index a6554ee..ee620c9 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -14,6 +14,7 @@ use std::convert::TryFrom;
 use std::f64;
 use std::hash::{Hash, Hasher};
 use std::marker::PhantomData;
+use std::cmp::max;
 
 use bit_vec::BitVec;
 #[cfg(feature = "random")]
@@ -220,7 +221,7 @@ impl<T: ?Sized> Bloom<T> {
     fn optimal_k_num(bitmap_bits: u64, items_count: usize) -> u32 {
         let m = bitmap_bits as f64;
         let n = items_count as f64;
-        let k_num = (m / n * f64::ln(2.0f64)).ceil() as u32;
+        let k_num = max((m / n * f64::ln(2.0f64)).floor() as u32, 1);
         cmp::max(k_num, 1)
     }