From a79c2d0af40a473dbd39de6a574ef6d2094ef943 Mon Sep 17 00:00:00 2001
From: shreyas-londhe <shreyas_londhe@outlook.com>
Date: Fri, 24 Jan 2025 00:00:08 +0530
Subject: [PATCH] feat: added fn drop_next_variable in SplitEqPoly

---
 jolt-core/src/poly/split_eq_poly.rs | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/jolt-core/src/poly/split_eq_poly.rs b/jolt-core/src/poly/split_eq_poly.rs
index 0fe169103..a812a5431 100644
--- a/jolt-core/src/poly/split_eq_poly.rs
+++ b/jolt-core/src/poly/split_eq_poly.rs
@@ -83,6 +83,21 @@ impl<F: JoltField> SplitEqPolynomial<F> {
             DensePolynomial::new(merged)
         }
     }
+
+    /// Drop the first variable from E1 or E2 table for Gruen's optimization
+    /// Before n/2: E1⁽ⁱ⁺¹⁾[x'] = eq(w[i+2:n/2], x')
+    /// After n/2:  E2⁽ⁱ⁺¹⁾[x'] = eq(w[i+2:n], x')
+    pub fn drop_next_variable(&mut self) {
+        if self.E1_len > 1 {
+            // Still in first phase (before n/2)
+            self.E1 = EqPolynomial::evals(&self.E1[1..self.E1_len]);
+            self.E1_len -= 1;
+        } else {
+            // In second phase (after n/2)
+            self.E2 = EqPolynomial::evals(&self.E2[1..self.E2_len]);
+            self.E2_len -= 1;
+        }
+    }
 }
 
 #[cfg(test)]