Add fan_out to Conv2dConfig::init (#1138)

burn-core/src/nn/conv/conv2d.rs

@@ -70,17 +70,22 @@ impl Conv2dConfig {
             self.kernel_size[1],
         ];
 
-        let fan_in = self.channels[0] / self.groups * self.kernel_size.iter().product::<usize>();
+        let k = self.kernel_size.iter().product::<usize>() / self.groups;
+        let fan_in = self.channels[0] * k;
+        let fan_out = self.channels[1] * k;
+
         let weight = self
             .initializer
-            .init_with(shape, Some(fan_in), None, device);
+            .init_with(shape, Some(fan_in), Some(fan_out), device);
         let mut bias = None;
 
         if self.bias {
-            bias = Some(
-                self.initializer
-                    .init_with([self.channels[1]], Some(fan_in), None, device),
-            );
+            bias = Some(self.initializer.init_with(
+                [self.channels[1]],
+                Some(fan_in),
+                Some(fan_out),
+                device,
+            ));
         }
 
         Conv2d {
@@ -161,4 +166,19 @@ mod tests {
             .to_data()
             .assert_approx_eq(&Data::zeros(conv.weight.shape()), 3);
     }
+
+    #[test]
+    fn initializer_fan_out() {
+        TestBackend::seed(0);
+
+        let init = Initializer::KaimingUniform {
+            gain: 1.0 / sqrt(3.0),
+            fan_out_only: true, // test that fan_out is passed to `init_with()`
+        };
+        let device = Default::default();
+        let config = Conv2dConfig::new([5, 1], [5, 5]).with_initializer(init.clone());
+        let _ = config.init::<TestBackend>(&device);
+
+        assert_eq!(config.initializer, init);
+    }
 }