Merge pull request #31 from lattice-complete/29_ceiling_k

fix: issue 29 use ceiling for size k

algebra/src/zq.rs

@@ -26,13 +26,19 @@ impl Zq {
         }
     }
 
-    pub fn value(&self) -> usize {
+    pub fn value(self) -> usize {
         self.value
     }
 
-    pub fn pow(&self, other: usize) -> Self {
+    pub fn pow(self, other: usize) -> Self {
         Zq::new(self.value.pow(other as u32))
     }
+
+    // bypass clippy for now as we'll implement Zq in isize/i64 (no div_ceil function supported) later
+    #[allow(clippy::manual_div_ceil)]
+    pub fn div_ceil(self, other: Zq) -> Zq {
+        Zq::new((self.value + other.value - 1) / other.value)
+    }
 }
 
 impl PartialOrd for Zq {
@@ -156,4 +162,17 @@ mod tests {
         let result = a % b;
         assert_eq!(result.value, 1);
     }
+
+    #[test]
+    fn test_zq_ceil_div() {
+        let mut a;
+        let mut b;
+        a = Zq::new(10);
+        b = Zq::new(3);
+        assert_eq!(a.div_ceil(b).value(), 4);
+
+        a = Zq::new(9);
+        b = Zq::new(3);
+        assert_eq!(a.div_ceil(b).value(), 3);
+    }
 }

labrador/src/prover.rs

@@ -295,8 +295,8 @@ pub fn prove(
     println!("Prover: Do aggregation");
     // 4. GOAL: Aggregation
     // 4.1 psi^(k) is randomly chosen from Z_q^{L}
-    // k = 1..λ/log2^q
-    let size_k = Zq::new(lambda.value() / log_q.value());
+    // k = 1..ceil(λ/log2^q)
+    let size_k = lambda.div_ceil(log_q);
     let psi: Vec<Vec<Zq>> = (0..size_k.value())
         .map(|_| {
             (0..constraint_num_l.value())