From 984f44b2817c1cacb513bcf35d2e883613d87625 Mon Sep 17 00:00:00 2001
From: wborgeaud <williamborgeaud@gmail.com>
Date: Tue, 1 Feb 2022 14:41:27 +0100
Subject: [PATCH] Fix lde -> coset_lde bug

---
 field/src/polynomial/mod.rs   | 5 +++++
 starky/src/fibonacci_stark.rs | 6 +++---
 starky/src/prover.rs          | 5 +++--
 3 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/field/src/polynomial/mod.rs b/field/src/polynomial/mod.rs
index 4264c914..d36757b3 100644
--- a/field/src/polynomial/mod.rs
+++ b/field/src/polynomial/mod.rs
@@ -57,6 +57,11 @@ impl<F: Field> PolynomialValues<F> {
         fft_with_options(coeffs, Some(rate_bits), None)
     }
 
+    pub fn coset_lde(self, rate_bits: usize) -> Self {
+        let coeffs = ifft(self).lde(rate_bits);
+        coeffs.coset_fft_with_options(F::coset_shift(), Some(rate_bits), None)
+    }
+
     pub fn degree(&self) -> usize {
         self.degree_plus_one()
             .checked_sub(1)
diff --git a/starky/src/fibonacci_stark.rs b/starky/src/fibonacci_stark.rs
index 488f1d46..1d760455 100644
--- a/starky/src/fibonacci_stark.rs
+++ b/starky/src/fibonacci_stark.rs
@@ -60,9 +60,9 @@ impl<F: RichField + Extendable<D>, const D: usize> Stark<F, D> for FibonacciStar
         P: PackedField<Scalar = FE>,
     {
         // Check public inputs.
-        // yield_constr.one_first_row(vars.local_values[0] - vars.public_inputs[Self::PI_INDEX_X0]);
-        // yield_constr.one_first_row(vars.local_values[1] - vars.public_inputs[Self::PI_INDEX_X1]);
-        // yield_constr.one_last_row(vars.local_values[1] - vars.public_inputs[Self::PI_INDEX_RES]);
+        yield_constr.one_first_row(vars.local_values[0] - vars.public_inputs[Self::PI_INDEX_X0]);
+        yield_constr.one_first_row(vars.local_values[1] - vars.public_inputs[Self::PI_INDEX_X1]);
+        yield_constr.one_last_row(vars.local_values[1] - vars.public_inputs[Self::PI_INDEX_RES]);
 
         // x0 <- x1
         yield_constr.one(vars.next_values[0] - vars.local_values[1]);
diff --git a/starky/src/prover.rs b/starky/src/prover.rs
index e9c31d98..352b03f7 100644
--- a/starky/src/prover.rs
+++ b/starky/src/prover.rs
@@ -1,6 +1,7 @@
 use anyhow::{ensure, Result};
 use itertools::Itertools;
 use plonky2::field::extension_field::Extendable;
+use plonky2::field::extension_field::FieldExtension;
 use plonky2::field::field_types::Field;
 use plonky2::field::polynomial::{PolynomialCoeffs, PolynomialValues};
 use plonky2::field::zero_poly_coset::ZeroPolyOnCoset;
@@ -169,13 +170,13 @@ where
     let lagrange_first = {
         let mut evals = PolynomialValues::new(vec![F::ZERO; degree]);
         evals.values[0] = F::ONE;
-        evals.lde(rate_bits)
+        evals.coset_lde(rate_bits)
     };
     // Evaluation of the last Lagrange polynomial on the LDE domain.
     let lagrange_last = {
         let mut evals = PolynomialValues::new(vec![F::ZERO; degree]);
         evals.values[degree - 1] = F::ONE;
-        evals.lde(rate_bits)
+        evals.coset_lde(rate_bits)
     };
 
     let z_h_on_coset = ZeroPolyOnCoset::<F>::new(degree_bits, rate_bits);