From f9df387118b4ae7614c21c5e7371aa0efe43035b Mon Sep 17 00:00:00 2001
From: zhenghaoz <zhangzhenghao@hotmail.com>
Date: Mon, 14 Feb 2022 21:01:32 +0800
Subject: [PATCH] return zero recall on empty ground truth (#381)

---
 base/search/hnsw.go | 3 +++
 base/search/ivf.go  | 3 +++
 2 files changed, 6 insertions(+)

diff --git a/base/search/hnsw.go b/base/search/hnsw.go
index 2a3580c39..b1e2665c0 100644
--- a/base/search/hnsw.go
+++ b/base/search/hnsw.go
@@ -349,6 +349,9 @@ func (b *HNSWBuilder) evaluate(idx *HNSW, prune0 bool) float32 {
 		}
 		return nil
 	})
+	if count == 0 {
+		return 0
+	}
 	return result / count
 }
 
diff --git a/base/search/ivf.go b/base/search/ivf.go
index b3e61fc0e..3bdcc08cc 100644
--- a/base/search/ivf.go
+++ b/base/search/ivf.go
@@ -302,6 +302,9 @@ func (b *IVFBuilder) evaluate(idx *IVF, prune0 bool) float32 {
 		}
 		return nil
 	})
+	if count == 0 {
+		return 0
+	}
 	return result / count
 }