From e82fb90c544627822a40bcd45f91ea7b945fd3ad Mon Sep 17 00:00:00 2001
From: Kristof Schroeder <kristof_schroeder@web.de>
Date: Thu, 13 Aug 2026 12:06:48 +0200
Subject: [PATCH] perf: concatenate per-chunk Schur edge lists in one pre-sized
 copy

---
 crates/within/src/block_elim/schur.rs | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/crates/within/src/block_elim/schur.rs b/crates/within/src/block_elim/schur.rs
index 77d0e90..70569e5 100644
--- a/crates/within/src/block_elim/schur.rs
+++ b/crates/within/src/block_elim/schur.rs
@@ -354,10 +354,9 @@ fn par_emit(matrix: &SddmMatrix, config: &ApproxSchurConfig) -> Vec<Edge> {
             },
         )
         .map(|work| work.edges)
-        .reduce(Vec::new, |mut a, mut b| {
-            a.append(&mut b);
-            a
-        });
+        // Pre-sized single copy; a `reduce` tree of `append`s recopies each edge per level.
+        .collect::<Vec<_>>()
+        .concat();
     if let Some(ground) = ground_vertex {
         edges.extend(
             matrix