From 23d2bde01f08352834de810e1d731c0a2137e944 Mon Sep 17 00:00:00 2001
From: Glenn Jocher <glenn.jocher@ultralytics.com>
Date: Sat, 1 Aug 2020 11:42:41 -0700
Subject: [PATCH] leaf variable --single-cls training bug fix (#593)

---
 utils/utils.py | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/utils/utils.py b/utils/utils.py
index 30a45b2..184e8dc 100755
--- a/utils/utils.py
+++ b/utils/utils.py
@@ -493,7 +493,8 @@ def compute_loss(p, targets, model):  # predictions, targets, model
     s = 3 / np  # output count scaling
     lbox *= h['giou'] * s
     lobj *= h['obj'] * s * (1.4 if np == 4 else 1.)
-    lcls *= h['cls'] * s
+    if model.nc > 1:
+        lcls *= h['cls'] * s
     bs = tobj.shape[0]  # batch size
 
     loss = lbox + lobj + lcls