From 667ee8338b5ab55f9024173787cd4f949e9dfd3c Mon Sep 17 00:00:00 2001
From: Matthew Kim <38759997+friendlymatthew@users.noreply.github.com>
Date: Mon, 3 Jun 2024 11:25:27 -0400
Subject: [PATCH] feat: from base queue (#321)

---
 pkg/hnsw/pq.go      | 10 ++++++++++
 pkg/hnsw/pq_test.go | 44 ++++++++++++++++++++++----------------------
 2 files changed, 32 insertions(+), 22 deletions(-)

diff --git a/pkg/hnsw/pq.go b/pkg/hnsw/pq.go
index 96dfd04..7eb21cd 100644
--- a/pkg/hnsw/pq.go
+++ b/pkg/hnsw/pq.go
@@ -149,3 +149,13 @@ func (bq *BaseQueue) update(item *Item, id Id, dist float32) {
 	item.dist = dist
 	heap.Fix(bq, item.index)
 }
+
+func FromBaseQueue(bq *BaseQueue, comparator Comparator) *BaseQueue {
+	newBq := NewBaseQueue(comparator)
+
+	for _, item := range bq.items {
+		newBq.Insert(item.id, item.dist)
+	}
+
+	return newBq
+}
diff --git a/pkg/hnsw/pq_test.go b/pkg/hnsw/pq_test.go
index bce3413..c98e223 100644
--- a/pkg/hnsw/pq_test.go
+++ b/pkg/hnsw/pq_test.go
@@ -45,7 +45,29 @@ func TestPQ(t *testing.T) {
 				t.Errorf("got %d, want %d", res, c.expected)
 			}
 		}
+	})
+
+	t.Run("interchange", func(t *testing.T) {
+		bq := NewBaseQueue(MinComparator{})
+		for i := 0; i < 100; i++ {
+			bq.Insert(Id(i), float32(i))
+		}
+
+		incBq := FromBaseQueue(bq, MaxComparator{})
+
+		i := Id(99)
+		for !incBq.IsEmpty() {
+			item, err := incBq.Peel()
+			if err != nil {
+				t.Fatal(err)
+			}
 
+			if item.id != i {
+				t.Fatalf("got %d, want %d", item.id, i)
+			}
+
+			i -= 1
+		}
 	})
 }
 
@@ -81,25 +103,3 @@ func furthestBuildings(heights []int, bricks, ladders int) (int, error) {
 
 	return len(heights) - 1, nil
 }
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