Merge pull request #286 from Qrlew/bug_gaussian_dp_query

fix gaussian dpevent
Qrlew · Jul 15, 2024 · 9f97f45 · 9f97f45
2 parents af7ad8f + 15ca915
commit 9f97f45
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diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+## [0.9.23] - 2024-07-9
+### Fixed
+- fixing noise multiplier of the gaussian dp event which should be independent from the sensitivity.
+
 ## [0.9.22] - 2024-07-9
 ### Changed
 - When translating relations to queries transform all nested CASE expressions into a single CASE

diff --git a/Cargo.toml b/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 authors = ["Nicolas Grislain <[email protected]>"]
 name = "qrlew"
-version = "0.9.22"
+version = "0.9.23"
 edition = "2021"
 description = "Sarus Qrlew Engine"
 documentation = "https://docs.rs/qrlew"

diff --git a/src/differential_privacy/aggregates.rs b/src/differential_privacy/aggregates.rs
@@ -101,7 +101,7 @@ impl Relation {
         }
         let number_of_agg = bounds.len() as f64;
         let (dp_relation, dp_event) = if number_of_agg > 0. {
-            let noise_multipliers = bounds
+            let gaussian_noises = bounds
                 .into_iter()
                 .map(|(name, bound)| {
                     (
@@ -114,15 +114,18 @@ impl Relation {
                     )
                 })
                 .collect::<Vec<_>>();
-            let dp_event = noise_multipliers
+            let dp_event = gaussian_noises
                 .iter()
-                .map(|(_, n)| DpEvent::gaussian(*n))
+                .map(|(_, n)| {
+                    if n > &0.0 {
+                        DpEvent::gaussian_from_epsilon_delta(epsilon, delta)
+                    } else {
+                        DpEvent::no_op()
+                    }
+                })
                 .collect::<Vec<_>>()
                 .into();
-            (
-                self.add_clipped_gaussian_noise(&noise_multipliers),
-                dp_event,
-            )
+            (self.add_clipped_gaussian_noise(&gaussian_noises), dp_event)
         } else {
             (self, DpEvent::no_op())
         };
@@ -660,7 +663,7 @@ mod tests {
             .unwrap();
         dp_relation.display_dot().unwrap();
         matches!(dp_relation.schema()[0].data_type(), DataType::Float(_));
-        assert!(dp_relation.dp_event().is_no_op()); // private query is null beacause we have computed the sum of zeros
+        assert!(dp_relation.dp_event().is_no_op()); // private query is null because we have computed the sum of zeros
 
         let query: &str = &ast::Query::from(&relation).to_string();
         println!("{query}");
@@ -1220,11 +1223,7 @@ mod tests {
             .unwrap();
         assert_eq!(
             dp_relation.dp_event(),
-            &DpEvent::gaussian_from_epsilon_delta_sensitivity(
-                parameters.epsilon,
-                parameters.delta,
-                2.
-            )
+            &DpEvent::gaussian_from_epsilon_delta(parameters.epsilon, parameters.delta,)
         );
         assert_eq!(
             dp_relation.relation().data_type(),
@@ -1242,11 +1241,7 @@ mod tests {
             .unwrap();
         assert_eq!(
             dp_relation.dp_event(),
-            &DpEvent::gaussian_from_epsilon_delta_sensitivity(
-                parameters.epsilon,
-                parameters.delta,
-                2.
-            )
+            &DpEvent::gaussian_from_epsilon_delta(parameters.epsilon, parameters.delta,)
         );
         assert_eq!(
             dp_relation.relation().data_type(),
@@ -1264,11 +1259,7 @@ mod tests {
         //dp_relation.relation().display_dot().unwrap();
         assert_eq!(
             dp_relation.dp_event(),
-            &DpEvent::gaussian_from_epsilon_delta_sensitivity(
-                parameters.epsilon,
-                parameters.delta,
-                2.
-            )
+            &DpEvent::gaussian_from_epsilon_delta(parameters.epsilon, parameters.delta,)
         );
         assert_eq!(
             dp_relation.relation().data_type(),
@@ -1287,11 +1278,7 @@ mod tests {
         //dp_relation.relation().display_dot().unwrap();
         assert_eq!(
             dp_relation.dp_event(),
-            &DpEvent::gaussian_from_epsilon_delta_sensitivity(
-                parameters.epsilon,
-                parameters.delta,
-                2.
-            )
+            &DpEvent::gaussian_from_epsilon_delta(parameters.epsilon, parameters.delta,)
         );
         assert_eq!(
             dp_relation.relation().data_type(),
@@ -1406,11 +1393,7 @@ mod tests {
         dp_relation.display_dot().unwrap();
         assert_eq!(
             dp_event,
-            DpEvent::gaussian_from_epsilon_delta_sensitivity(
-                parameters.epsilon,
-                parameters.delta,
-                10.
-            )
+            DpEvent::gaussian_from_epsilon_delta(parameters.epsilon, parameters.delta,)
         );
         assert_eq!(
             dp_relation.data_type(),
@@ -1433,15 +1416,85 @@ mod tests {
         dp_relation.display_dot().unwrap();
         assert_eq!(
             dp_event,
-            DpEvent::gaussian_from_epsilon_delta_sensitivity(
-                parameters.epsilon,
-                parameters.delta,
-                10.
-            )
+            DpEvent::gaussian_from_epsilon_delta(parameters.epsilon, parameters.delta,)
         );
         assert_eq!(
             dp_relation.data_type(),
             DataType::structured([("sum_a", DataType::float_interval(0., 1000.)),])
         );
     }
+
+    #[test]
+    fn test_gaussian_dp_event_independent_from_bounds() {
+        let parameters = DpAggregatesParameters::from_dp_parameters(
+            DpParameters::from_epsilon_delta(1.0, 1e-3),
+            1.,
+        );
+
+        let table: Relation = Relation::table()
+            .name("table")
+            .schema(
+                Schema::builder()
+                    .with(("a", DataType::float_interval(-1.0, 1.0)))
+                    .with((
+                        PrivacyUnit::privacy_unit(),
+                        DataType::integer_range(1..=100),
+                    ))
+                    .with((
+                        PrivacyUnit::privacy_unit_weight(),
+                        DataType::float_interval(0., 1.),
+                    ))
+                    .build(),
+            )
+            .size(100)
+            .build();
+
+        let reduce: Reduce = Relation::reduce()
+            .name("reduce_relation")
+            .with(("sum_a".to_string(), AggregateColumn::sum("a")))
+            .input(table.clone())
+            .build();
+        let (dp_relation, dp_event) = reduce
+            .differentially_private_aggregates(parameters.clone())
+            .unwrap()
+            .into();
+        dp_relation.display_dot().unwrap();
+        assert_eq!(
+            dp_event,
+            DpEvent::gaussian_from_epsilon_delta(parameters.epsilon, parameters.delta,)
+        );
+
+        let table: Relation = Relation::table()
+            .name("table")
+            .schema(
+                Schema::builder()
+                    .with(("a", DataType::float_interval(-100.0, 100.0)))
+                    .with((
+                        PrivacyUnit::privacy_unit(),
+                        DataType::integer_range(1..=100),
+                    ))
+                    .with((
+                        PrivacyUnit::privacy_unit_weight(),
+                        DataType::float_interval(0., 1.),
+                    ))
+                    .build(),
+            )
+            .size(100)
+            .build();
+
+        let reduce: Reduce = Relation::reduce()
+            .name("reduce_relation")
+            .with(("sum_a".to_string(), AggregateColumn::sum("a")))
+            .input(table.clone())
+            .build();
+        let (dp_relation, dp_event) = reduce
+            .differentially_private_aggregates(parameters.clone())
+            .unwrap()
+            .into();
+        dp_relation.display_dot().unwrap();
+        assert_eq!(
+            dp_event,
+            DpEvent::gaussian_from_epsilon_delta(parameters.epsilon, parameters.delta,)
+        );
+    }
 }
diff --git a/src/differential_privacy/dp_event.rs b/src/differential_privacy/dp_event.rs
@@ -120,13 +120,9 @@ impl DpEvent {
         }
     }
 
-    pub fn gaussian_from_epsilon_delta_sensitivity(
-        epsilon: f64,
-        delta: f64,
-        sensitivity: f64,
-    ) -> Self {
+    pub fn gaussian_from_epsilon_delta(epsilon: f64, delta: f64) -> Self {
         DpEvent::Gaussian {
-            noise_multiplier: gaussian_noise(epsilon, delta, sensitivity),
+            noise_multiplier: gaussian_noise_multiplier(epsilon, delta),
         }
     }
 }
@@ -165,7 +161,12 @@ impl From<Vec<DpEvent>> for DpEvent {
 
 pub fn gaussian_noise(epsilon: f64, delta: f64, sensitivity: f64) -> f64 {
     // it can be inf so we clamp the results between 0 and f64::MAX
-    ((2. * (1.25_f64 / delta).ln()).sqrt() * sensitivity / epsilon).clamp(0.0, f64::MAX)
+    (gaussian_noise_multiplier(epsilon, delta) * sensitivity).clamp(0.0, f64::MAX)
+}
+
+pub fn gaussian_noise_multiplier(epsilon: f64, delta: f64) -> f64 {
+    // it can be inf so we clamp the results between 0 and f64::MAX
+    ((2. * (1.25_f64 / delta).ln()).sqrt() / epsilon).clamp(0.0, f64::MAX)
 }
 
 pub fn gaussian_tau(epsilon: f64, delta: f64, sensitivity: f64) -> f64 {

diff --git a/src/differential_privacy/mod.rs b/src/differential_privacy/mod.rs
@@ -659,10 +659,9 @@ mod tests {
                 parameters.epsilon * parameters.tau_thresholding_share,
                 parameters.delta * parameters.tau_thresholding_share
             )
-            .compose(DpEvent::gaussian_from_epsilon_delta_sensitivity(
+            .compose(DpEvent::gaussian_from_epsilon_delta(
                 parameters.epsilon * (1. - parameters.tau_thresholding_share),
                 parameters.delta * (1. - parameters.tau_thresholding_share),
-                10.
             ))
         );
         let correct_schema: Schema = vec![