From 2f2de13887045645b14c73051aab908807ddb11c Mon Sep 17 00:00:00 2001
From: therealyingtong <yingtong@z.cash>
Date: Fri, 12 Feb 2021 09:40:53 +0800
Subject: [PATCH] Calculate required degree of lookup

---
 src/plonk.rs        |  2 +-
 src/plonk/lookup.rs | 13 +++++++++++--
 2 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/src/plonk.rs b/src/plonk.rs
index 205613b..4e147d1 100644
--- a/src/plonk.rs
+++ b/src/plonk.rs
@@ -472,7 +472,7 @@ fn test_proving() {
             let sl_ = meta.query_any(sl.into(), Rotation::cur());
             let sl2_ = meta.query_any(sl2.into(), Rotation::cur());
             meta.lookup(&[a_.clone()], &[sl_.clone()]);
-            meta.lookup(&[a_ + b_], &[sl_ + sl2_]);
+            meta.lookup(&[a_ * b_], &[sl_ * sl2_]);
 
             meta.create_gate("Combined add-mult", |meta| {
                 let d = meta.query_advice(d, Rotation::next());
diff --git a/src/plonk/lookup.rs b/src/plonk/lookup.rs
index 6755d05..e632c08 100644
--- a/src/plonk/lookup.rs
+++ b/src/plonk/lookup.rs
@@ -25,7 +25,7 @@ impl<F: Field> Argument<F> {
         // degree 2:
         // l_0(X) * (1 - z'(X)) = 0
         //
-        // degree 3:
+        // degree (1 + input_degree + table_degree):
         // z'(X) (a'(X) + \beta) (s'(X) + \gamma)
         // - z'(\omega^{-1} X) (\theta^{m-1} a_0(X) + ... + a_{m-1}(X) + \beta) (\theta^{m-1} s_0(X) + ... + s_{m-1}(X) + \gamma)
         //
@@ -34,6 +34,15 @@ impl<F: Field> Argument<F> {
         //
         // degree 2:
         // (a′(X)−s′(X))⋅(a′(X)−a′(\omega{-1} X)) = 0
-        3
+        let mut input_degree = 1;
+        for expr in self.input_columns.iter() {
+            input_degree = std::cmp::max(input_degree, expr.degree());
+        }
+        let mut table_degree = 1;
+        for expr in self.table_columns.iter() {
+            table_degree = std::cmp::max(table_degree, expr.degree());
+        }
+
+        1 + input_degree + table_degree
     }
 }