From 73b53196dce3d7ac9527183bb3f6134c3cb5f30e Mon Sep 17 00:00:00 2001
From: Ryan Kim <chokobole33@gmail.com>
Date: Thu, 31 Oct 2024 13:42:30 +0900
Subject: [PATCH] perf(crypto): optimize `TwoAdicFri::CreateOpeningProof()`

- parallelize copy.
- merge `ReverseMatrixIndexBits()` into one single parallel loop.
---
 tachyon/crypto/commitments/fri/two_adic_fri.h | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/tachyon/crypto/commitments/fri/two_adic_fri.h b/tachyon/crypto/commitments/fri/two_adic_fri.h
index 0bfbd6ab6..96fb7721d 100644
--- a/tachyon/crypto/commitments/fri/two_adic_fri.h
+++ b/tachyon/crypto/commitments/fri/two_adic_fri.h
@@ -148,9 +148,13 @@ class TwoAdicFRI {
             reduced_openings[log_num_rows];
         CHECK_EQ(reduced_opening_for_log_num_rows.size(), num_rows);
 
-        math::RowMajorMatrix<F> block =
-            mat.topRows(num_rows >> config_.log_blowup);
-        ReverseMatrixIndexBits(block);
+        math::RowMajorMatrix<F> block;
+        block.resize(num_rows >> config_.log_blowup, mat.cols());
+        OMP_PARALLEL_FOR(size_t row = 0; row < num_rows >> config_.log_blowup;
+                         ++row) {
+          block.row(row) = mat.row(base::bits::ReverseBitsLen(
+              row, log_num_rows - config_.log_blowup));
+        }
         std::vector<ExtF> reduced_rows = DotExtPowers(mat, alpha);
 
         // TODO(ashjeong): Determine if using a matrix is a better fit.