From 8c5cbbc7c66a51c805003dfcce5ed02d472cf99d Mon Sep 17 00:00:00 2001
From: wborgeaud <williamborgeaud@gmail.com>
Date: Tue, 22 Feb 2022 17:40:48 +0100
Subject: [PATCH] Add first row Z check

---
 starky/src/permutation.rs | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/starky/src/permutation.rs b/starky/src/permutation.rs
index dad4b661..d2a16fc4 100644
--- a/starky/src/permutation.rs
+++ b/starky/src/permutation.rs
@@ -264,7 +264,12 @@ pub(crate) fn eval_permutation_checks<F, FE, C, S, const D: usize, const D2: usi
         next_zs,
         permutation_challenge_sets,
     } = permutation_data;
-    // TODO: Z_1 check.
+
+    // Check that Z(1) = 1;
+    for &z in &local_zs {
+        consumer.constraint_first_row(z - FE::ONE);
+    }
+
     let permutation_pairs = stark.permutation_pairs();
 
     let permutation_batches = get_permutation_batches(
@@ -326,7 +331,14 @@ pub(crate) fn eval_permutation_checks_recursively<F, S, const D: usize>(
         next_zs,
         permutation_challenge_sets,
     } = permutation_data;
-    // TODO: Z_1 check.
+
+    let one = builder.one_extension();
+    // Check that Z(1) = 1;
+    for &z in &local_zs {
+        let z_1 = builder.sub_extension(z, one);
+        consumer.constraint_first_row(builder, z_1);
+    }
+
     let permutation_pairs = stark.permutation_pairs();
 
     let permutation_batches = get_permutation_batches(