YOLOv5 AWS Inferentia Inplace compatibility updates (#2953)

* Added flag to enable/disable all inplace and assignment operations

* Removed shape print statements

* Scope Detect/Model import to avoid circular dependency

* PEP8

* create _descale_pred()

* replace lost space

* replace list with tuple

Co-authored-by: Glenn Jocher <glenn.jocher@ultralytics.com>

models/experimental.py

@@ -110,7 +110,9 @@ class Ensemble(nn.ModuleList):
         return y, None  # inference, train output
 
 
-def attempt_load(weights, map_location=None):
+def attempt_load(weights, map_location=None, inplace=True):
+    from models.yolo import Detect, Model
+
     # Loads an ensemble of models weights=[a,b,c] or a single model weights=[a] or weights=a
     model = Ensemble()
     for w in weights if isinstance(weights, list) else [weights]:
@@ -120,8 +122,8 @@ def attempt_load(weights, map_location=None):
 
     # Compatibility updates
     for m in model.modules():
-        if type(m) in [nn.Hardswish, nn.LeakyReLU, nn.ReLU, nn.ReLU6, nn.SiLU]:
-            m.inplace = True  # pytorch 1.7.0 compatibility
+        if type(m) in [nn.Hardswish, nn.LeakyReLU, nn.ReLU, nn.ReLU6, nn.SiLU, Detect, Model]:
+            m.inplace = inplace  # pytorch 1.7.0 compatibility
         elif type(m) is Conv:
             m._non_persistent_buffers_set = set()  # pytorch 1.6.0 compatibility
 

models/yolo.py

@@ -26,7 +26,7 @@ class Detect(nn.Module):
     stride = None  # strides computed during build
     export = False  # onnx export
 
-    def __init__(self, nc=80, anchors=(), ch=()):  # detection layer
+    def __init__(self, nc=80, anchors=(), ch=(), inplace=True):  # detection layer
         super(Detect, self).__init__()
         self.nc = nc  # number of classes
         self.no = nc + 5  # number of outputs per anchor
@@ -37,6 +37,7 @@ class Detect(nn.Module):
         self.register_buffer('anchors', a)  # shape(nl,na,2)
         self.register_buffer('anchor_grid', a.clone().view(self.nl, 1, -1, 1, 1, 2))  # shape(nl,1,na,1,1,2)
         self.m = nn.ModuleList(nn.Conv2d(x, self.no * self.na, 1) for x in ch)  # output conv
+        self.inplace = inplace  # use in-place ops (e.g. slice assignment)
 
     def forward(self, x):
         # x = x.copy()  # for profiling
@@ -52,8 +53,13 @@ class Detect(nn.Module):
                     self.grid[i] = self._make_grid(nx, ny).to(x[i].device)
 
                 y = x[i].sigmoid()
-                y[..., 0:2] = (y[..., 0:2] * 2. - 0.5 + self.grid[i]) * self.stride[i]  # xy
-                y[..., 2:4] = (y[..., 2:4] * 2) ** 2 * self.anchor_grid[i]  # wh
+                if self.inplace:
+                    y[..., 0:2] = (y[..., 0:2] * 2. - 0.5 + self.grid[i]) * self.stride[i]  # xy
+                    y[..., 2:4] = (y[..., 2:4] * 2) ** 2 * self.anchor_grid[i]  # wh
+                else:  # for YOLOv5 on AWS Inferentia https://github.com/ultralytics/yolov5/pull/2953
+                    xy = (y[..., 0:2] * 2. - 0.5 + self.grid[i]) * self.stride[i]  # xy
+                    wh = (y[..., 2:4] * 2) ** 2 * self.anchor_grid[i]  # wh
+                    y = torch.cat((xy, wh, y[..., 4:]), -1)
                 z.append(y.view(bs, -1, self.no))
 
         return x if self.training else (torch.cat(z, 1), x)
@@ -85,12 +91,14 @@ class Model(nn.Module):
             self.yaml['anchors'] = round(anchors)  # override yaml value
         self.model, self.save = parse_model(deepcopy(self.yaml), ch=[ch])  # model, savelist
         self.names = [str(i) for i in range(self.yaml['nc'])]  # default names
+        self.inplace = self.yaml.get('inplace', True)
         # logger.info([x.shape for x in self.forward(torch.zeros(1, ch, 64, 64))])
 
         # Build strides, anchors
         m = self.model[-1]  # Detect()
         if isinstance(m, Detect):
             s = 256  # 2x min stride
+            m.inplace = self.inplace
             m.stride = torch.tensor([s / x.shape[-2] for x in self.forward(torch.zeros(1, ch, s, s))])  # forward
             m.anchors /= m.stride.view(-1, 1, 1)
             check_anchor_order(m)
@@ -105,24 +113,23 @@ class Model(nn.Module):
 
     def forward(self, x, augment=False, profile=False):
         if augment:
-            img_size = x.shape[-2:]  # height, width
-            s = [1, 0.83, 0.67]  # scales
-            f = [None, 3, None]  # flips (2-ud, 3-lr)
-            y = []  # outputs
-            for si, fi in zip(s, f):
-                xi = scale_img(x.flip(fi) if fi else x, si, gs=int(self.stride.max()))
-                yi = self.forward_once(xi)[0]  # forward
-                # cv2.imwrite(f'img_{si}.jpg', 255 * xi[0].cpu().numpy().transpose((1, 2, 0))[:, :, ::-1])  # save
-                yi[..., :4] /= si  # de-scale
-                if fi == 2:
-                    yi[..., 1] = img_size[0] - yi[..., 1]  # de-flip ud
-                elif fi == 3:
-                    yi[..., 0] = img_size[1] - yi[..., 0]  # de-flip lr
-                y.append(yi)
-            return torch.cat(y, 1), None  # augmented inference, train
+            return self.forward_augment(x)  # augmented inference, None
         else:
             return self.forward_once(x, profile)  # single-scale inference, train
 
+    def forward_augment(self, x):
+        img_size = x.shape[-2:]  # height, width
+        s = [1, 0.83, 0.67]  # scales
+        f = [None, 3, None]  # flips (2-ud, 3-lr)
+        y = []  # outputs
+        for si, fi in zip(s, f):
+            xi = scale_img(x.flip(fi) if fi else x, si, gs=int(self.stride.max()))
+            yi = self.forward_once(xi)[0]  # forward
+            # cv2.imwrite(f'img_{si}.jpg', 255 * xi[0].cpu().numpy().transpose((1, 2, 0))[:, :, ::-1])  # save
+            yi = self._descale_pred(yi, fi, si, img_size)
+            y.append(yi)
+        return torch.cat(y, 1), None  # augmented inference, train
+
     def forward_once(self, x, profile=False):
         y, dt = [], []  # outputs
         for m in self.model:
@@ -146,6 +153,23 @@ class Model(nn.Module):
             logger.info('%.1fms total' % sum(dt))
         return x
 
+    def _descale_pred(self, p, flips, scale, img_size):
+        # de-scale predictions following augmented inference (inverse operation)
+        if self.inplace:
+            p[..., :4] /= scale  # de-scale
+            if flips == 2:
+                p[..., 1] = img_size[0] - p[..., 1]  # de-flip ud
+            elif flips == 3:
+                p[..., 0] = img_size[1] - p[..., 0]  # de-flip lr
+        else:
+            x, y, wh = p[..., 0:1] / scale, p[..., 1:2] / scale, p[..., 2:4] / scale  # de-scale
+            if flips == 2:
+                y = img_size[0] - y  # de-flip ud
+            elif flips == 3:
+                x = img_size[1] - x  # de-flip lr
+            p = torch.cat((x, y, wh, p[..., 4:]), -1)
+        return p
+
     def _initialize_biases(self, cf=None):  # initialize biases into Detect(), cf is class frequency
         # https://arxiv.org/abs/1708.02002 section 3.3
         # cf = torch.bincount(torch.tensor(np.concatenate(dataset.labels, 0)[:, 0]).long(), minlength=nc) + 1.