From 6eb1fb00779ab9a2c076972cc8e17479950383a6 Mon Sep 17 00:00:00 2001
From: Filip <filip.haltmayer@gmail.com>
Date: Wed, 12 Jul 2023 22:23:33 +0000
Subject: [PATCH] Threadpool based HNSW insert

Signed-off-by: Filip <filip.haltmayer@gmail.com>
---
 .gitignore             |  1 +
 src/index/hnsw/hnsw.cc | 13 +++++++++++--
 2 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/.gitignore b/.gitignore
index 5b5a5e347..256d07b2a 100644
--- a/.gitignore
+++ b/.gitignore
@@ -12,6 +12,7 @@
 .vscode
 docker-compose-devcontainer.yml
 docker-compose-devcontainer.yml.tmp
+.devcontainer/
 
 *.code-workspace
 
diff --git a/src/index/hnsw/hnsw.cc b/src/index/hnsw/hnsw.cc
index d5704ca54..ea9ebdcec 100644
--- a/src/index/hnsw/hnsw.cc
+++ b/src/index/hnsw/hnsw.cc
@@ -83,10 +83,19 @@ class HnswIndexNode : public IndexNode {
         auto hnsw_cfg = static_cast<const HnswConfig&>(cfg);
         index_->addPoint(tensor, 0);
 
-#pragma omp parallel for
+        std::vector<std::future<void>> futures;
+        futures.reserve(rows);
+
         for (int i = 1; i < rows; ++i) {
-            index_->addPoint(((const char*)tensor + index_->data_size_ * i), i);
+            futures.push_back(pool_->push([&, idx = i]() {
+                index_->addPoint(((const char*)tensor + index_->data_size_ * idx), idx);
+            }));
         }
+
+        for (auto& future : futures) {
+            future.get();
+        }
+
         build_time.RecordSection("");
         LOG_KNOWHERE_INFO_ << "HNSW built with #points num:" << index_->max_elements_ << " #M:" << index_->M_
                            << " #max level:" << index_->maxlevel_ << " #ef_construction:" << index_->ef_construction_