diff --git a/detect.py b/detect.py
index 8cdc0af..fdbefd3 100644
--- a/detect.py
+++ b/detect.py
@@ -76,7 +76,7 @@ def detect(save_img=False):
 
         # Apply NMS
         pred = non_max_suppression(pred, opt.conf_thres, opt.iou_thres,
-                                   multi_label=False, classes=opt.classes, agnostic=opt.agnostic_nms)
+                                   fast=True, classes=opt.classes, agnostic=opt.agnostic_nms)
 
         # Apply Classifier
         if classify:
diff --git a/test.py b/test.py
index ce1ad08..1e21dd7 100644
--- a/test.py
+++ b/test.py
@@ -19,7 +19,7 @@ def test(data,
          augment=False,
          model=None,
          dataloader=None,
-         multi_label=True,
+         fast=False,
          verbose=False):  # 0 fast, 1 accurate
     # Initialize/load model and set device
     if model is None:
@@ -92,7 +92,7 @@ def test(data,
 
             # Run NMS
             t = torch_utils.time_synchronized()
-            output = non_max_suppression(inf_out, conf_thres=conf_thres, iou_thres=iou_thres, multi_label=multi_label)
+            output = non_max_suppression(inf_out, conf_thres=conf_thres, iou_thres=iou_thres, fast=fast)
             t1 += torch_utils.time_synchronized() - t
 
         # Statistics per image
diff --git a/train.py b/train.py
index c6c1f7f..27228cd 100644
--- a/train.py
+++ b/train.py
@@ -293,13 +293,13 @@ def train(hyp):
         final_epoch = epoch + 1 == epochs
         if not opt.notest or final_epoch:  # Calculate mAP
             results, maps, times = test.test(opt.data,
-                                      batch_size=batch_size,
-                                      imgsz=imgsz_test,
-                                      save_json=final_epoch and opt.data.endswith(os.sep + 'coco.yaml'),
-                                      model=ema.ema,
-                                      single_cls=opt.single_cls,
-                                      dataloader=testloader,
-                                      multi_label=ni > n_burn)
+                                             batch_size=batch_size,
+                                             imgsz=imgsz_test,
+                                             save_json=final_epoch and opt.data.endswith(os.sep + 'coco.yaml'),
+                                             model=ema.ema,
+                                             single_cls=opt.single_cls,
+                                             dataloader=testloader,
+                                             fast=ni > n_burn)
 
         # Write
         with open(results_file, 'a') as f:
@@ -325,10 +325,10 @@ def train(hyp):
         if save:
             with open(results_file, 'r') as f:  # create checkpoint
                 ckpt = {'epoch': epoch,
-                         'best_fitness': best_fitness,
-                         'training_results': f.read(),
-                         'model': ema.ema.module if hasattr(model, 'module') else ema.ema,
-                         'optimizer': None if final_epoch else optimizer.state_dict()}
+                        'best_fitness': best_fitness,
+                        'training_results': f.read(),
+                        'model': ema.ema.module if hasattr(model, 'module') else ema.ema,
+                        'optimizer': None if final_epoch else optimizer.state_dict()}
 
             # Save last, best and delete
             torch.save(ckpt, last)
diff --git a/utils/utils.py b/utils/utils.py
index 40432fe..3899231 100755
--- a/utils/utils.py
+++ b/utils/utils.py
@@ -19,7 +19,7 @@ import torchvision
 from scipy.signal import butter, filtfilt
 from tqdm import tqdm
 
-from . import torch_utils, google_utils  # torch_utils, google_utils
+from . import torch_utils, google_utils  #  torch_utils, google_utils
 
 # Set printoptions
 torch.set_printoptions(linewidth=320, precision=5, profile='long')
@@ -460,29 +460,33 @@ def build_targets(p, targets, model):
 
     return tcls, tbox, indices, anch
 
-
-def non_max_suppression(prediction, conf_thres=0.1, iou_thres=0.6, multi_label=True, classes=None, agnostic=False):
+def non_max_suppression(prediction, conf_thres=0.1, iou_thres=0.6, fast=False, classes=None, agnostic=False):
     """
     Performs  Non-Maximum Suppression on inference results
     Returns detections with shape:
         nx6 (x1, y1, x2, y2, conf, cls)
     """
+    nc = prediction[0].shape[1] - 5  # number of classes
 
     # Settings
-    merge = True  # merge for best mAP
     min_wh, max_wh = 2, 4096  # (pixels) minimum and maximum box width and height
     max_det = 300  # maximum number of detections per image
     time_limit = 10.0  # seconds to quit after
-    redundant = conf_thres == 0.001  # require redundant detections
+    redundant = True  # require redundant detections
+    fast |= conf_thres > 0.001  # fast mode
+    if fast:
+        merge = False
+        multi_label = False
+    else:
+        merge = True  # merge for best mAP (adds 0.5ms/img)
+        multi_label = nc > 1  # multiple labels per box (adds 0.5ms/img)
 
     t = time.time()
-    nc = prediction[0].shape[1] - 5  # number of classes
-    multi_label &= nc > 1  # multiple labels per box
     output = [None] * prediction.shape[0]
     for xi, x in enumerate(prediction):  # image index, image inference
         # Apply constraints
+        # x[((x[..., 2:4] < min_wh) | (x[..., 2:4] > max_wh)).any(1), 4] = 0  # width-height
         x = x[x[:, 4] > conf_thres]  # confidence
-        # x = x[((x[:, 2:4] > min_wh) & (x[:, 2:4] < max_wh)).all(1)]  # width-height
 
         # If none remain process next image
         if not x.shape[0]: