From e1c336b99c5b0e7ebbb2bd00adc957845c206b5d Mon Sep 17 00:00:00 2001
From: thealmarty <“thealmartyblog@gmail.com”>
Date: Mon, 18 Mar 2024 09:49:05 -0700
Subject: [PATCH] Fix constraint and test.

---
 alu_u32/src/lt/columns.rs | 2 +-
 alu_u32/src/lt/mod.rs     | 2 +-
 alu_u32/src/lt/stark.rs   | 7 ++-----
 3 files changed, 4 insertions(+), 7 deletions(-)

diff --git a/alu_u32/src/lt/columns.rs b/alu_u32/src/lt/columns.rs
index 633baf2..55fa10c 100644
--- a/alu_u32/src/lt/columns.rs
+++ b/alu_u32/src/lt/columns.rs
@@ -10,7 +10,7 @@ pub struct Lt32Cols<T> {
     pub input_2: Word<T>,
 
     /// Boolean flags indicating which byte pair differs
-    pub byte_flag: [T; 3],
+    pub byte_flag: [T; 4],
 
     /// Bit decomposition of 256 + input_1 - input_2
     pub bits: [T; 10],
diff --git a/alu_u32/src/lt/mod.rs b/alu_u32/src/lt/mod.rs
index c6ea04b..59f2aba 100644
--- a/alu_u32/src/lt/mod.rs
+++ b/alu_u32/src/lt/mod.rs
@@ -121,7 +121,7 @@ impl Lt32Chip {
             for i in 0..10 {
                 cols.bits[i] = F::from_canonical_u16(z >> i & 1);
             }
-            if n < 3 {
+            if n < 4 {
                 cols.byte_flag[n] = F::one();
             }
         }
diff --git a/alu_u32/src/lt/stark.rs b/alu_u32/src/lt/stark.rs
index 44e7cb2..2180ce5 100644
--- a/alu_u32/src/lt/stark.rs
+++ b/alu_u32/src/lt/stark.rs
@@ -68,13 +68,10 @@ where
             .when_ne(local.bits[8], AB::Expr::one())
             .assert_one(local.output);
         // output should be 1 if is_lte & input_1 == input_2
+        let all_flag_sum = flag_sum + local.byte_flag[3];
         builder
             .when(local.is_lte)
-            .when_ne(flag_sum, AB::Expr::one())
-            .when_ne(
-                AB::Expr::from_canonical_u32(256) + local.input_1[3] - local.input_2[3],
-                AB::Expr::one(),
-            )
+            .when_ne(all_flag_sum, AB::Expr::one())
             .assert_one(local.output);
 
         // Check bit decomposition