UNet shrinking

sCOCA_ML/models/UNet_models.py

@@ -1,18 +1,12 @@
+"""
+3D U-Net model with optional FiLM layers for style conditioning.
+This model implements a 3D U-Net architecture with downsampling and upsampling blocks, and skip connections.
+"""
+
 import torch
 import torch.nn as nn
-import torch.nn.functional as F
 from .base_class_models import BaseModel
-
-class FiLM(nn.Module):
-    def __init__(self, num_features, style_dim):
-        super(FiLM, self).__init__()
-        self.gamma = nn.Linear(style_dim, num_features)
-        self.beta = nn.Linear(style_dim, num_features)
-
-    def forward(self, x, style):
-        gamma = self.gamma(style).unsqueeze(-1).unsqueeze(-1).unsqueeze(-1)
-        beta = self.beta(style).unsqueeze(-1).unsqueeze(-1).unsqueeze(-1)
-        return gamma * x + beta
+from .FiLM import FiLM
 
 class UNetBlock(nn.Module):
     def __init__(self, in_channels, out_channels, style_dim=None):
@@ -48,7 +42,8 @@ class UNetDecLayer(nn.Module):
 
     def forward(self, x, skip_connection, style=None):
         x = self.up(x)
-        x = torch.cat([x, skip_connection], dim=1)
+        if skip_connection is not None:
+            x = torch.cat([x, skip_connection], dim=1)
         return self.block(x, style)
 
 class UNet3D(BaseModel):
@@ -125,3 +120,70 @@ class UNet3D(BaseModel):
         
         return self.final(out)
         
+class UNet3D_Shrink(BaseModel):
+    
+    def __init__(self,
+                 N: int = 128,
+                 in_channels: int = 2,
+                 out_channels: int = 1,
+                 style_dim: int = 2,
+                 device: torch.device = torch.device('cpu'),
+                 first_layer_channel_exponent: int = 3,
+                 shrink_factor_exponent: int = 1,
+                 ):
+        """
+        A 3D U-Net model with optional FiLM layers for style conditioning and a shrink factor.
+        It means that the output data is of size (N/shrink_factor, N/shrink_factor, N/shrink_factor), where N is the input size.
+        """
+        super().__init__(N=N,
+                         in_channels=in_channels,
+                         out_channels=out_channels,
+                         style_parameters=style_dim,
+                         device=device)
+        import numpy as np
+        
+        self.depth_enc = np.floor(np.log2(N)).astype(int) - 1 # Depth of the U-Net based on input size N
+        self.depth_dec = self.depth_enc - shrink_factor_exponent # Depth of the U-Net based on input size N and shrink factor
+        self.first_layer_channel_exponent = first_layer_channel_exponent
+        self.shrink_factor_exponent = shrink_factor_exponent
+        
+        self.enc = []
+        for i in range(self.depth_enc):
+            in_ch = in_channels if i == 0 else 2**(self.first_layer_channel_exponent + i - 1)
+            out_ch = 2**(self.first_layer_channel_exponent + i)
+            self.enc.append(UNetEncLayer(in_ch, out_ch, style_dim))
+        
+        self.enc = nn.ModuleList(self.enc)
+        
+        self.bottleneck = UNetBlock(2**(self.first_layer_channel_exponent + self.depth_enc - 1),
+                                    2**(self.first_layer_channel_exponent + self.depth_enc), style_dim)
+        
+        self.dec = []
+        for i in range(self.depth_dec - 1, -1, -1):
+            in_ch = 2**(self.first_layer_channel_exponent + i + 1)
+            out_ch = 2**(self.first_layer_channel_exponent + i)
+            skip_conn_ch = out_ch if i >= self.depth_dec-self.depth_enc else 0
+            self.dec.append(UNetDecLayer(in_ch, out_ch, skip_conn_ch, style_dim))
+        
+        self.dec = nn.ModuleList(self.dec)
+        
+        self.final = nn.Conv3d(2**(self.first_layer_channel_exponent), out_channels, kernel_size=1)
+        
+    
+    def forward(self, x, style):
+        out = x
+        outlist = []
+
+        for i in range(self.depth_enc):
+            skip, out = self.enc[i](out, style)
+            outlist.append(skip)
+
+        out = self.bottleneck(out, style)
+
+        for i in range(self.depth_dec):
+            if i < self.depth_enc:
+                out = self.dec[i](out, outlist[self.depth_enc - 1 - i], style)
+            else:
+                out = self.dec[i](out, None, style)
+        
+        return self.final(out)