From 8f18089aac2dc01094d1db893e5d33ec2ec56135 Mon Sep 17 00:00:00 2001
From: wborgeaud <williamborgeaud@gmail.com>
Date: Fri, 23 Jul 2021 18:06:14 +0200
Subject: [PATCH] Implement `eval_unfiltered_recursively` for `ReducingGate`

---
 src/field/extension_field/target.rs |  7 +++++++
 src/gates/reducing.rs               | 28 +++++++++++++++++++++++++++-
 2 files changed, 34 insertions(+), 1 deletion(-)

diff --git a/src/field/extension_field/target.rs b/src/field/extension_field/target.rs
index 6083e2c4..97576ac6 100644
--- a/src/field/extension_field/target.rs
+++ b/src/field/extension_field/target.rs
@@ -115,6 +115,13 @@ impl<F: Extendable<D>, const D: usize> CircuitBuilder<F, D> {
         arr[0] = t;
         ExtensionTarget(arr)
     }
+
+    pub fn convert_to_ext_algebra(&mut self, et: ExtensionTarget<D>) -> ExtensionAlgebraTarget<D> {
+        let zero = self.zero_extension();
+        let mut arr = [zero; D];
+        arr[0] = et;
+        ExtensionAlgebraTarget(arr)
+    }
 }
 
 /// Flatten the slice by sending every extension target to its D-sized canonical representation.
diff --git a/src/gates/reducing.rs b/src/gates/reducing.rs
index ebcd5cac..4c750bb9 100644
--- a/src/gates/reducing.rs
+++ b/src/gates/reducing.rs
@@ -82,7 +82,33 @@ impl<F: Extendable<D>, const D: usize> Gate<F, D> for ReducingGate<D> {
         builder: &mut CircuitBuilder<F, D>,
         vars: EvaluationTargets<D>,
     ) -> Vec<ExtensionTarget<D>> {
-        todo!()
+        let output = vars.get_local_ext_algebra(Self::wires_output());
+        let alpha = vars.get_local_ext_algebra(Self::wires_alpha());
+        let old_acc = vars.get_local_ext_algebra(Self::wires_old_acc());
+        let coeffs = self
+            .wires_coeffs()
+            .map(|i| vars.local_wires[i])
+            .collect::<Vec<_>>();
+        let accs = (0..self.num_coeffs)
+            .map(|i| vars.get_local_ext_algebra(self.wires_accs(i)))
+            .collect::<Vec<_>>();
+
+        let mut constraints = Vec::new();
+        let mut acc = old_acc;
+        for i in 0..self.num_coeffs {
+            let mut tmp = builder.mul_ext_algebra(acc, alpha);
+            let coeff = builder.convert_to_ext_algebra(coeffs[i]);
+            tmp = builder.add_ext_algebra(tmp, coeff);
+            tmp = builder.sub_ext_algebra(tmp, accs[i]);
+            constraints.push(tmp);
+            acc = accs[i];
+        }
+
+        constraints.push(builder.sub_ext_algebra(output, acc));
+        constraints
+            .into_iter()
+            .flat_map(|alg| alg.to_ext_target_array())
+            .collect()
     }
 
     fn generators(