refactor: Reorganize prover steps

Specifically: move sampling of quotients weights closer to calculation
of quotient codewords, with an eye to merging the two.

triton-vm/src/stark.rs

@@ -176,15 +176,26 @@ impl Stark {
 
         prof_start!(maybe_profiler, "Fiat-Shamir", "hash");
         proof_stream.enqueue(ProofItem::MerkleRoot(ext_merkle_tree.root()));
+
+        // Get the weights with which to compress the many quotients into one.
+        let quotient_combination_weights =
+            proof_stream.sample_scalars(MasterExtTable::NUM_CONSTRAINTS);
+        let quotient_combination_weights = Array1::from(quotient_combination_weights);
         prof_stop!(maybe_profiler, "Fiat-Shamir");
         prof_stop!(maybe_profiler, "ext tables");
 
+        // low-degree extend the trace codewords so that the all quotient codewords
+        // obtained by element-wise evaluation of the AIR constraints
         prof_start!(maybe_profiler, "quotient-domain codewords");
         let base_quotient_domain_codewords = master_base_table.quotient_domain_table();
         let ext_quotient_domain_codewords = master_ext_table.quotient_domain_table();
         prof_stop!(maybe_profiler, "quotient-domain codewords");
 
-        prof_start!(maybe_profiler, "quotient codewords");
+        prof_start!(
+            maybe_profiler,
+            "compute and combine quotient codewords",
+            "CC"
+        );
         let master_quotient_table = all_quotients(
             base_quotient_domain_codewords,
             ext_quotient_domain_codewords,
@@ -193,24 +204,14 @@ impl Stark {
             &challenges,
             maybe_profiler,
         );
-        prof_stop!(maybe_profiler, "quotient codewords");
-
-        prof_start!(maybe_profiler, "linearly combine quotient codewords", "CC");
-        // Create quotient codeword. This is a part of the combination codeword. To reduce the
-        // amount of hashing necessary, the quotient codeword is linearly summed instead of
-        // hashed prior to committing to it.
-        let quotient_combination_weights =
-            proof_stream.sample_scalars(MasterExtTable::NUM_CONSTRAINTS);
-        let quotient_combination_weights = Array1::from(quotient_combination_weights);
         assert_eq!(
             quotient_combination_weights.len(),
             master_quotient_table.ncols()
         );
-
         let quotient_codeword =
             Self::random_linear_sum(master_quotient_table.view(), quotient_combination_weights);
         assert_eq!(quotient_domain.length, quotient_codeword.len());
-        prof_stop!(maybe_profiler, "linearly combine quotient codewords");
+        prof_stop!(maybe_profiler, "compute and combine quotient codewords");
 
         prof_start!(maybe_profiler, "commit to quotient codeword segments");
         prof_start!(maybe_profiler, "LDE", "LDE");

triton-vm/src/table/extension_table.rs

@@ -18,6 +18,9 @@ use crate::arithmetic_domain::ArithmeticDomain;
 use crate::table::challenges::Challenges;
 use crate::table::master_table::MasterExtTable;
 
+/// The implementations of these functions are automatically generated using the
+/// command `cargo run --bin constraint-evaluation-generator` and live in
+/// `constraints.rs`.
 pub trait Evaluable<FF: FiniteField> {
     /// The code for this method must be generated by running
     /// `cargo run --bin constraint-evaluation-generator`