4757 update patch merging (#4758)

* update patch merging

Signed-off-by: Wenqi Li <[email protected]>

* fixes unit tests

Signed-off-by: Wenqi Li <[email protected]>

monai/networks/nets/__init__.py

@@ -81,7 +81,7 @@
     seresnext50,
     seresnext101,
 )
-from .swin_unetr import SwinUNETR
+from .swin_unetr import PatchMerging, PatchMergingV2, SwinUNETR
 from .torchvision_fc import TorchVisionFCModel
 from .transchex import BertAttention, BertMixedLayer, BertOutput, BertPreTrainedModel, MultiModal, Pooler, Transchex
 from .unet import UNet, Unet

monai/networks/nets/swin_unetr.py

@@ -9,7 +9,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from typing import Sequence, Tuple, Type, Union
+from typing import Optional, Sequence, Tuple, Type, Union
 
 import numpy as np
 import torch
@@ -21,10 +21,23 @@
 from monai.networks.blocks import MLPBlock as Mlp
 from monai.networks.blocks import PatchEmbed, UnetOutBlock, UnetrBasicBlock, UnetrUpBlock
 from monai.networks.layers import DropPath, trunc_normal_
-from monai.utils import ensure_tuple_rep, optional_import
+from monai.utils import ensure_tuple_rep, look_up_option, optional_import
 
 rearrange, _ = optional_import("einops", name="rearrange")
 
+__all__ = [
+    "SwinUNETR",
+    "window_partition",
+    "window_reverse",
+    "WindowAttention",
+    "SwinTransformerBlock",
+    "PatchMerging",
+    "PatchMergingV2",
+    "MERGING_MODE",
+    "BasicLayer",
+    "SwinTransformer",
+]
+
 
 class SwinUNETR(nn.Module):
     """
@@ -48,6 +61,7 @@ def __init__(
         normalize: bool = True,
         use_checkpoint: bool = False,
         spatial_dims: int = 3,
+        downsample="merging",
     ) -> None:
         """
         Args:
@@ -64,6 +78,9 @@ def __init__(
             normalize: normalize output intermediate features in each stage.
             use_checkpoint: use gradient checkpointing for reduced memory usage.
             spatial_dims: number of spatial dims.
+            downsample: module used for downsampling, available options are `"mergingv2"`, `"merging"` and a
+                user-specified `nn.Module` following the API defined in :py:class:`monai.networks.nets.PatchMerging`.
+                The default is currently `"merging"` (the original version defined in v0.9.0).
 
         Examples::
 
@@ -121,6 +138,7 @@ def __init__(
             norm_layer=nn.LayerNorm,
             use_checkpoint=use_checkpoint,
             spatial_dims=spatial_dims,
+            downsample=look_up_option(downsample, MERGING_MODE) if isinstance(downsample, str) else downsample,
         )
 
         self.encoder1 = UnetrBasicBlock(
@@ -657,7 +675,7 @@ def forward(self, x, mask_matrix):
         return x
 
 
-class PatchMerging(nn.Module):
+class PatchMergingV2(nn.Module):
     """
     Patch merging layer based on: "Liu et al.,
     Swin Transformer: Hierarchical Vision Transformer using Shifted Windows
@@ -695,8 +713,8 @@ def forward(self, x):
             x2 = x[:, 0::2, 1::2, 0::2, :]
             x3 = x[:, 0::2, 0::2, 1::2, :]
             x4 = x[:, 1::2, 0::2, 1::2, :]
-            x5 = x[:, 0::2, 1::2, 0::2, :]
-            x6 = x[:, 0::2, 0::2, 1::2, :]
+            x5 = x[:, 1::2, 1::2, 0::2, :]
+            x6 = x[:, 0::2, 1::2, 1::2, :]
             x7 = x[:, 1::2, 1::2, 1::2, :]
             x = torch.cat([x0, x1, x2, x3, x4, x5, x6, x7], -1)
 
@@ -716,6 +734,36 @@ def forward(self, x):
         return x
 
 
+class PatchMerging(PatchMergingV2):
+    """The `PatchMerging` module previously defined in v0.9.0."""
+
+    def forward(self, x):
+        x_shape = x.size()
+        if len(x_shape) == 4:
+            return super().forward(x)
+        if len(x_shape) != 5:
+            raise ValueError(f"expecting 5D x, got {x.shape}.")
+        b, d, h, w, c = x_shape
+        pad_input = (h % 2 == 1) or (w % 2 == 1) or (d % 2 == 1)
+        if pad_input:
+            x = F.pad(x, (0, 0, 0, w % 2, 0, h % 2, 0, d % 2))
+        x0 = x[:, 0::2, 0::2, 0::2, :]
+        x1 = x[:, 1::2, 0::2, 0::2, :]
+        x2 = x[:, 0::2, 1::2, 0::2, :]
+        x3 = x[:, 0::2, 0::2, 1::2, :]
+        x4 = x[:, 1::2, 0::2, 1::2, :]
+        x5 = x[:, 0::2, 1::2, 0::2, :]
+        x6 = x[:, 0::2, 0::2, 1::2, :]
+        x7 = x[:, 1::2, 1::2, 1::2, :]
+        x = torch.cat([x0, x1, x2, x3, x4, x5, x6, x7], -1)
+        x = self.norm(x)
+        x = self.reduction(x)
+        return x
+
+
+MERGING_MODE = {"merging": PatchMerging, "mergingv2": PatchMergingV2}
+
+
 def compute_mask(dims, window_size, shift_size, device):
     """Computing region masks based on: "Liu et al.,
     Swin Transformer: Hierarchical Vision Transformer using Shifted Windows
@@ -776,7 +824,7 @@ def __init__(
         drop: float = 0.0,
         attn_drop: float = 0.0,
         norm_layer: Type[LayerNorm] = nn.LayerNorm,
-        downsample: isinstance = None,  # type: ignore
+        downsample: Optional[nn.Module] = None,
         use_checkpoint: bool = False,
     ) -> None:
         """
@@ -791,7 +839,7 @@ def __init__(
             drop: dropout rate.
             attn_drop: attention dropout rate.
             norm_layer: normalization layer.
-            downsample: downsample layer at the end of the layer.
+            downsample: an optional downsampling layer at the end of the layer.
             use_checkpoint: use gradient checkpointing for reduced memory usage.
         """
 
@@ -820,7 +868,7 @@ def __init__(
             ]
         )
         self.downsample = downsample
-        if self.downsample is not None:
+        if callable(self.downsample):
             self.downsample = downsample(dim=dim, norm_layer=norm_layer, spatial_dims=len(self.window_size))
 
     def forward(self, x):
@@ -881,6 +929,7 @@ def __init__(
         patch_norm: bool = False,
         use_checkpoint: bool = False,
         spatial_dims: int = 3,
+        downsample="merging",
     ) -> None:
         """
         Args:
@@ -899,6 +948,9 @@ def __init__(
             patch_norm: add normalization after patch embedding.
             use_checkpoint: use gradient checkpointing for reduced memory usage.
             spatial_dims: spatial dimension.
+            downsample: module used for downsampling, available options are `"mergingv2"`, `"merging"` and a
+                user-specified `nn.Module` following the API defined in :py:class:`monai.networks.nets.PatchMerging`.
+                The default is currently `"merging"` (the original version defined in v0.9.0).
         """
 
         super().__init__()
@@ -920,6 +972,7 @@ def __init__(
         self.layers2 = nn.ModuleList()
         self.layers3 = nn.ModuleList()
         self.layers4 = nn.ModuleList()
+        down_sample_mod = look_up_option(downsample, MERGING_MODE) if isinstance(downsample, str) else downsample
         for i_layer in range(self.num_layers):
             layer = BasicLayer(
                 dim=int(embed_dim * 2**i_layer),
@@ -932,7 +985,7 @@ def __init__(
                 drop=drop_rate,
                 attn_drop=attn_drop_rate,
                 norm_layer=norm_layer,
-                downsample=PatchMerging,
+                downsample=down_sample_mod,
                 use_checkpoint=use_checkpoint,
             )
             if i_layer == 0:

tests/test_swin_unetr.py

@@ -16,12 +16,14 @@
 from parameterized import parameterized
 
 from monai.networks import eval_mode
-from monai.networks.nets.swin_unetr import PatchMerging, SwinUNETR
+from monai.networks.nets.swin_unetr import PatchMerging, PatchMergingV2, SwinUNETR
 from monai.utils import optional_import
 
 einops, has_einops = optional_import("einops")
 
 TEST_CASE_SWIN_UNETR = []
+case_idx = 0
+test_merging_mode = ["mergingv2", "merging", PatchMerging, PatchMergingV2]
 for attn_drop_rate in [0.4]:
     for in_channels in [1]:
         for depth in [[2, 1, 1, 1], [1, 2, 1, 1]]:
@@ -39,10 +41,12 @@
                                     "depths": depth,
                                     "norm_name": norm_name,
                                     "attn_drop_rate": attn_drop_rate,
+                                    "downsample": test_merging_mode[case_idx % 4],
                                 },
                                 (2, in_channels, *img_size),
                                 (2, out_channels, *img_size),
                             ]
+                            case_idx += 1
                             TEST_CASE_SWIN_UNETR.append(test_case)
 
 

tests/utils.py

@@ -17,6 +17,7 @@
 import operator
 import os
 import queue
+import ssl
 import sys
 import tempfile
 import time
@@ -123,6 +124,9 @@ def skip_if_downloading_fails():
         yield
     except (ContentTooShortError, HTTPError, ConnectionError) as e:
         raise unittest.SkipTest(f"error while downloading: {e}") from e
+    except ssl.SSLError as ssl_e:
+        if "decryption failed" in str(ssl_e):
+            raise unittest.SkipTest(f"SSL error while downloading: {ssl_e}") from ssl_e
     except RuntimeError as rt_e:
         if "unexpected EOF" in str(rt_e):
             raise unittest.SkipTest(f"error while downloading: {rt_e}") from rt_e  # incomplete download