wip

math/src/ring/impl_u64/rescaling_rns.rs

@@ -0,0 +1,56 @@
+use crate::ring::RingRNS;
+use crate::poly::PolyRNS;
+use crate::modulus::barrett::Barrett;
+use crate::modulus::ONCE;
+extern crate test;
+
+impl RingRNS<'_, u64>{
+
+    /// Updates b to floor(b / q[b.level()]).
+    /// Expects a and b to be in the NTT domain.
+    pub fn div_floor_by_last_modulus_ntt(&self, a: &PolyRNS<u64>, buf: &mut PolyRNS<u64>, b: &mut PolyRNS<u64>){
+        assert!(b.level() >= a.level()-1, "invalid input b: b.level()={} < a.level()-1={}", b.level(), a.level()-1);
+        let level = self.level();
+        self.0[level].intt::<true>(a.at(level), buf.at_mut(0));
+        let rescaling_constants: Vec<Barrett<u64>> = self.rescaling_constant();
+        let (buf_ntt_q_scaling, buf_ntt_qi_scaling) = buf.0.split_at_mut(1);
+        for (i, r) in self.0[0..level].iter().enumerate(){
+            r.ntt::<true>(&buf_ntt_q_scaling[0], &mut buf_ntt_qi_scaling[0]);
+            r.sum_aqqmb_prod_c_scalar_barrett::<ONCE>(&buf_ntt_qi_scaling[0], a.at(i), &rescaling_constants[i], b.at_mut(i));
+        }
+    }
+
+    /// Updates b to floor(b / q[b.level()]).
+    pub fn div_floor_by_last_modulus(&self, a: &PolyRNS<u64>, b: &mut PolyRNS<u64>){
+        assert!(b.level() >= a.level()-1, "invalid input b: b.level()={} < a.level()-1={}", b.level(), a.level()-1);
+        let level = self.level();
+        let rescaling_constants: Vec<Barrett<u64>> = self.rescaling_constant();
+        for (i, r) in self.0[0..level].iter().enumerate(){
+            r.sum_aqqmb_prod_c_scalar_barrett::<ONCE>(a.at(level), a.at(i), &rescaling_constants[i], b.at_mut(i));
+        }
+    }
+}
+
+
+#[cfg(test)]
+mod tests {
+    use crate::ring::Ring;
+    use crate::ring::impl_u64::ring_rns::new_rings;
+    use super::*;
+
+    #[test]
+    fn test_div_floor_by_last_modulus_ntt() {
+        let n = 1<<10;
+        let moduli: Vec<u64> = vec![0x1fffffffffe00001u64, 0x1fffffffffc80001u64];
+        let rings: Vec<Ring<u64>> = new_rings(n, moduli);
+        let ring_rns = RingRNS::new(&rings);
+
+        let a: PolyRNS<u64> = ring_rns.new_polyrns();
+        let mut b: PolyRNS<u64> = ring_rns.new_polyrns();
+        let mut c: PolyRNS<u64> = ring_rns.new_polyrns();
+
+        ring_rns.div_floor_by_last_modulus_ntt(&a, &mut b, &mut c);
+
+    	//assert!(m_precomp.mul_external::<ONCE>(y_mont, x) == (x as u128 * y as u128 % q as u128) as u64);
+    }
+}