From d95d7422d688f94cd1d5208405062fd04e367320 Mon Sep 17 00:00:00 2001
From: Alon Haramati <91828241+alonh5@users.noreply.github.com>
Date: Wed, 27 Mar 2024 16:46:38 +0200
Subject: [PATCH] Semantic quotient changes. (#544)

---
 src/core/backend/cpu/quotients.rs       | 24 +++++++++++++-----------
 src/core/commitment_scheme/quotients.rs | 12 ++++++------
 2 files changed, 19 insertions(+), 17 deletions(-)

diff --git a/src/core/backend/cpu/quotients.rs b/src/core/backend/cpu/quotients.rs
index e46dd3234..af650595c 100644
--- a/src/core/backend/cpu/quotients.rs
+++ b/src/core/backend/cpu/quotients.rs
@@ -17,14 +17,14 @@ impl QuotientOps for CPUBackend {
         domain: CircleDomain,
         columns: &[&CircleEvaluation<Self, BaseField, BitReversedOrder>],
         random_coeff: SecureField,
-        samples: &[ColumnSampleBatch],
+        sample_batches: &[ColumnSampleBatch],
     ) -> SecureColumn<Self> {
         let mut res = SecureColumn::zeros(domain.size());
         for row in 0..domain.size() {
             // TODO(alonh): Make an efficient bit reverse domain iterator, possibly for AVX backend.
             let domain_point = domain.at(bit_reverse_index(row, domain.log_size()));
             let row_value =
-                accumulate_row_quotients(samples, columns, row, random_coeff, domain_point);
+                accumulate_row_quotients(sample_batches, columns, row, random_coeff, domain_point);
             res.set(row, row_value);
         }
         res
@@ -32,32 +32,34 @@ impl QuotientOps for CPUBackend {
 }
 
 pub fn accumulate_row_quotients(
-    samples: &[ColumnSampleBatch],
+    sample_batches: &[ColumnSampleBatch],
     columns: &[&CircleEvaluation<CPUBackend, BaseField, BitReversedOrder>],
     row: usize,
     random_coeff: SecureField,
     domain_point: CirclePoint<BaseField>,
 ) -> SecureField {
-    let mut row_accumlator = SecureField::zero();
-    for sample in samples {
+    let mut row_accumulator = SecureField::zero();
+    for sample_batch in sample_batches {
         let mut numerator = SecureField::zero();
-        for (column_index, sampled_value) in &sample.columns_and_values {
+        for (column_index, sampled_value) in &sample_batch.columns_and_values {
             let column = &columns[*column_index];
             let value = column[row];
-            let linear_term = complex_conjugate_line(sample.point, *sampled_value, domain_point);
+            let linear_term =
+                complex_conjugate_line(sample_batch.point, *sampled_value, domain_point);
             numerator = numerator * random_coeff + value - linear_term;
         }
 
         let denominator = pair_vanishing(
-            sample.point,
-            sample.point.complex_conjugate(),
+            sample_batch.point,
+            sample_batch.point.complex_conjugate(),
             domain_point.into_ef(),
         );
 
-        row_accumlator = row_accumlator * random_coeff.pow(sample.columns_and_values.len() as u128)
+        row_accumulator = row_accumulator
+            * random_coeff.pow(sample_batch.columns_and_values.len() as u128)
             + numerator / denominator;
     }
-    row_accumlator
+    row_accumulator
 }
 
 #[cfg(test)]
diff --git a/src/core/commitment_scheme/quotients.rs b/src/core/commitment_scheme/quotients.rs
index d4d7be58d..513961ca8 100644
--- a/src/core/commitment_scheme/quotients.rs
+++ b/src/core/commitment_scheme/quotients.rs
@@ -28,7 +28,7 @@ pub trait QuotientOps: Backend {
         domain: CircleDomain,
         columns: &[&CircleEvaluation<Self, BaseField, BitReversedOrder>],
         random_coeff: SecureField,
-        samples: &[ColumnSampleBatch],
+        sample_batches: &[ColumnSampleBatch],
     ) -> SecureColumn<Self>;
 }
 
@@ -43,7 +43,7 @@ impl ColumnSampleBatch {
     /// Groups column samples by sampled point.
     /// # Arguments
     /// samples: For each column, a vector of samples.
-    pub fn new(samples: &[&Vec<PointSample>]) -> Vec<Self> {
+    pub fn new_vec(samples: &[&Vec<PointSample>]) -> Vec<Self> {
         // Group samples by point, and create a ColumnSampleBatch for each point.
         // This should keep a stable ordering.
         let mut grouped_samples = BTreeMap::new();
@@ -83,8 +83,8 @@ pub fn compute_fri_quotients<B: QuotientOps>(
             let (columns, samples): (Vec<_>, Vec<_>) = tuples.unzip();
             let domain = CanonicCoset::new(log_size).circle_domain();
             // TODO: slice.
-            let batched_samples = ColumnSampleBatch::new(&samples);
-            let values = B::accumulate_quotients(domain, &columns, random_coeff, &batched_samples);
+            let sample_batches = ColumnSampleBatch::new_vec(&samples);
+            let values = B::accumulate_quotients(domain, &columns, random_coeff, &sample_batches);
             SecureEvaluation { domain, values }
         })
         .collect()
@@ -123,7 +123,7 @@ pub fn fri_answers_for_log_size(
     queried_values_per_column: &[&Vec<BaseField>],
 ) -> Result<SparseCircleEvaluation<SecureField>, VerificationError> {
     let commitment_domain = CanonicCoset::new(log_size).circle_domain();
-    let batched_samples = ColumnSampleBatch::new(samples);
+    let sample_batches = ColumnSampleBatch::new_vec(samples);
     for queried_values in queried_values_per_column {
         if queried_values.len() != query_domain.flatten().len() {
             return Err(VerificationError::InvalidStructure(
@@ -152,7 +152,7 @@ pub fn fri_answers_for_log_size(
         for row in 0..domain.size() {
             let domain_point = domain.at(bit_reverse_index(row, log_size));
             let value = accumulate_row_quotients(
-                &batched_samples,
+                &sample_batches,
                 &column_evals.iter().collect_vec(),
                 row,
                 random_coeff,