From 7690d09fb82ee856dd711e2be666f667b9d45df0 Mon Sep 17 00:00:00 2001
From: Dirkjan Ochtman <dirkjan@ochtman.nl>
Date: Thu, 21 Jan 2021 14:40:48 +0100
Subject: [PATCH] Bump M up to 32

---
 Cargo.toml   | 4 ++++
 src/lib.rs   | 2 +-
 src/types.rs | 9 ++++++++-
 3 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/Cargo.toml b/Cargo.toml
index 200b7a9..d1ee291 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -5,6 +5,9 @@ license = "MIT OR Apache-2.0"
 authors = ["Dirkjan Ochtman <dirkjan@ochtman.nl>"]
 edition = "2018"
 
+[features]
+with-serde = ["serde", "serde-big-array"]
+
 [dependencies]
 indicatif = { version = "0.15", optional = true }
 num_cpus = "1.13"
@@ -13,6 +16,7 @@ parking_lot = "0.11"
 rand = { version = "0.8", features = ["small_rng"] }
 rayon = "1.5"
 serde = { version = "1.0.118", features = ["derive"], optional = true }
+serde-big-array = { version = "0.3.1", optional = true }
 
 [dev-dependencies]
 bencher = "0.1.5"
diff --git a/src/lib.rs b/src/lib.rs
index af7ed2d..a59c068 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -675,4 +675,4 @@ pub trait Point: Clone + Sync {
 /// The parameter `M` from the paper
 ///
 /// This should become a generic argument to `Hnsw` when possible.
-const M: usize = 12;
+const M: usize = 32;
diff --git a/src/types.rs b/src/types.rs
index 4431342..fa94948 100644
--- a/src/types.rs
+++ b/src/types.rs
@@ -7,6 +7,8 @@ use rand::rngs::SmallRng;
 use rand::Rng;
 #[cfg(feature = "serde")]
 use serde::{Deserialize, Serialize};
+#[cfg(feature = "serde-big-array")]
+use serde_big_array::big_array;
 
 use crate::{Hnsw, Point, M};
 
@@ -80,7 +82,12 @@ impl<'a> Layer for &'a [UpperNode] {
 
 #[cfg_attr(feature = "serde", derive(Deserialize, Serialize))]
 #[derive(Clone, Copy, Debug)]
-pub(crate) struct ZeroNode(pub(crate) [PointId; M * 2]);
+pub(crate) struct ZeroNode(
+    #[cfg_attr(feature = "serde", serde(with = "BigArray"))] pub(crate) [PointId; M * 2],
+);
+
+#[cfg(feature = "serde-big-array")]
+big_array! { BigArray; }
 
 impl ZeroNode {
     pub(crate) fn rewrite(&mut self, mut iter: impl Iterator<Item = PointId>) {