Add rounding versions of size methods on Count

crates/geo_filters/README.md

@@ -33,8 +33,7 @@ c2.push(2);
 c2.push(3);
 
 let estimated_size = c1.size_with_sketch(&c2);
-assert!(estimated_size >= 3.0_f32 * 0.9 &&
-        estimated_size <= 3.0_f32 * 1.1);
+assert_eq!(estimated_size, 3);
 ```
 
 ## Background

crates/geo_filters/src/config.rs

@@ -374,7 +374,7 @@ pub(crate) mod tests {
                 m.push_hash(rnd.next_u64());
             }
             // Compute the relative error between estimate and actually inserted items.
-            let high_precision = m.size() / cnt as f32 - 1.0;
+            let high_precision = m.size_real() / cnt as f32 - 1.0;
             // Take the average over trials many attempts.
             avg_precision += high_precision / trials as f32;
             avg_var += high_precision.powf(2.0) / trials as f32;

crates/geo_filters/src/diff_count.rs

@@ -443,11 +443,11 @@ impl<C: GeoConfig<Diff>> Count<Diff> for GeoDiffCount<'_, C> {
         *self = xor(self, other);
     }
 
-    fn size(&self) -> f32 {
+    fn size_real(&self) -> f32 {
         self.estimate_size()
     }
 
-    fn size_with_sketch(&self, other: &Self) -> f32 {
+    fn size_with_sketch_real(&self, other: &Self) -> f32 {
         assert!(
             self.config == other.config,
             "combined filters must have the same configuration"
@@ -501,7 +501,7 @@ mod tests {
             let mut geo_count = GeoDiffCount13::default();
 
             (0..n).for_each(|i| geo_count.push(i));
-            assert_eq!(result, geo_count.size());
+            assert_eq!(result, geo_count.size_real());
         }
     }
 

crates/geo_filters/src/distinct_count.rs

@@ -143,7 +143,7 @@ impl<C: GeoConfig<Distinct>> Count<Distinct> for GeoDistinctCount<'_, C> {
         *self = or(self, other)
     }
 
-    fn size(&self) -> f32 {
+    fn size_real(&self) -> f32 {
         let lowest_bucket = self.lsb.bit_range().start;
         let total = self.msb.len()
             + self
@@ -159,7 +159,7 @@ impl<C: GeoConfig<Distinct>> Count<Distinct> for GeoDistinctCount<'_, C> {
         }
     }
 
-    fn size_with_sketch(&self, other: &Self) -> f32 {
+    fn size_with_sketch_real(&self, other: &Self) -> f32 {
         assert!(
             self.config == other.config,
             "combined filters must have the same configuration"
@@ -272,7 +272,7 @@ mod tests {
         ] {
             let mut geo_count = GeoDistinctCount13::default();
             (0..n).for_each(|i| geo_count.push(i));
-            assert_eq!(result, geo_count.size());
+            assert_eq!(result, geo_count.size_real());
         }
     }
 

crates/geo_filters/src/evaluation/hll.rs

@@ -126,11 +126,11 @@ impl<C: HllConfig> Count<Distinct> for Hll<C> {
         unimplemented!()
     }
 
-    fn size(&self) -> f32 {
+    fn size_real(&self) -> f32 {
         self.inner.borrow_mut().count() as f32
     }
 
-    fn size_with_sketch(&self, _other: &Self) -> f32 {
+    fn size_with_sketch_real(&self, _other: &Self) -> f32 {
         unimplemented!()
     }
 

crates/geo_filters/src/evaluation/simulation.rs

@@ -25,7 +25,7 @@ impl<C: GeoConfig<Diff> + Clone> SimulationCount for GeoDiffCount<'_, C> {
         <Self as Count<_>>::push_hash(self, hash)
     }
     fn size(&self) -> f32 {
-        <Self as Count<_>>::size(self)
+        <Self as Count<_>>::size_real(self)
     }
     fn bytes_in_memory(&self) -> usize {
         <Self as Count<_>>::bytes_in_memory(self)
@@ -36,7 +36,7 @@ impl<C: GeoConfig<Distinct>> SimulationCount for GeoDistinctCount<'_, C> {
         <Self as Count<_>>::push_hash(self, hash)
     }
     fn size(&self) -> f32 {
-        <Self as Count<_>>::size(self)
+        <Self as Count<_>>::size_real(self)
     }
     fn bytes_in_memory(&self) -> usize {
         <Self as Count<_>>::bytes_in_memory(self)
@@ -47,7 +47,7 @@ impl<C: HllConfig> SimulationCount for Hll<C> {
         <Self as Count<_>>::push_hash(self, hash)
     }
     fn size(&self) -> f32 {
-        <Self as Count<_>>::size(self)
+        <Self as Count<_>>::size_real(self)
     }
     fn bytes_in_memory(&self) -> usize {
         <Self as Count<_>>::bytes_in_memory(self)

crates/geo_filters/src/lib.rs

@@ -43,17 +43,44 @@ pub trait Count<M: Method> {
     /// If only the size of the combined set is needed, [`Self::size_with_sketch`] is more efficient and should be used.
     fn push_sketch(&mut self, other: &Self);
 
-    /// Return the estimated set size.
-    fn size(&self) -> f32;
+    /// Return the estimated set size rounded to the nearest unsigned integer.
+    fn size(&self) -> usize {
+        let size = self.size_real().round();
+        debug_assert_f32s_in_range(size);
+        size as usize
+    }
 
-    /// Return the estimated set size when combined with the given sketch.
+    /// Return the estimated set size as a real number.
+    fn size_real(&self) -> f32;
+
+    /// Return the estimated set size when combined with the given sketch rounded to the nearest unsigned integer.
+    /// If the combined set itself is not going to be used, this method is more efficient than using [`Self::push_sketch`] and [`Self::size`].
+    fn size_with_sketch(&self, other: &Self) -> usize {
+        let size = self.size_with_sketch_real(other).round();
+        debug_assert_f32s_in_range(size);
+        size as usize
+    }
+
+    /// Return the estimated set size when combined with the given sketch as a real number.
     /// If the combined set itself is not going to be used, this method is more efficient than using [`Self::push_sketch`] and [`Self::size`].
-    fn size_with_sketch(&self, other: &Self) -> f32;
+    fn size_with_sketch_real(&self, other: &Self) -> f32;
 
     /// Returns the number of bytes in memory used to represent this filter.
     fn bytes_in_memory(&self) -> usize;
 }
 
+#[inline]
+fn debug_assert_f32s_in_range(v: f32) {
+    // The geometric filter should never produce these values.
+    // These assertions failing indicates that there is a bug.
+    debug_assert!(v.is_finite(), "Estimated size must be finite, got {v}");
+    debug_assert!(v >= 0.0, "Estimated size must be non-negative, got {v}");
+    debug_assert!(
+        v <= usize::MAX as f32,
+        "Estimated size {v} exceeds usize::MAX",
+    );
+}
+
 #[doc = include_str!("../README.md")]
 #[cfg(doctest)]
 pub struct ReadmeDocTests;