From de59161686b63ad336d3ef603df99e030cf595c1 Mon Sep 17 00:00:00 2001
From: Luc Grosheintz <luc.grosheintz@gmail.ch>
Date: Wed, 18 Oct 2023 18:34:08 +0200
Subject: [PATCH] Use `RawIndex = std::vector<std::array<.., 2>>`.

The memory layout of an `std::vector<std::array<...>>` is better than
`std::vector<std::vector<...>>`. This allows HighFive to avoid numerous
allocations and copies.
---
 src/edge_index.cpp | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/edge_index.cpp b/src/edge_index.cpp
index e5468b9d..ba3c6c8a 100644
--- a/src/edge_index.cpp
+++ b/src/edge_index.cpp
@@ -15,6 +15,7 @@
 #include <set>
 #include <unordered_map>
 #include <vector>
+#include <array>
 
 
 namespace bbp {
@@ -23,7 +24,7 @@ namespace edge_index {
 
 namespace {
 
-using RawIndex = std::vector<std::vector<uint64_t>>;
+using RawIndex = std::vector<std::array<uint64_t, 2>>;
 
 const char* const SOURCE_NODE_ID_DSET = "source_node_id";
 const char* const TARGET_NODE_ID_DSET = "target_node_id";