Pass the correct "input" values to the sub-layers during the Backward pass

akropp · akropp · commit fd105b8edd16 · 2023-05-25T12:16:14.000-04:00
diff --git a/src/mlpack/methods/ann/layer/multi_layer_impl.hpp b/src/mlpack/methods/ann/layer/multi_layer_impl.hpp
@@ -182,10 +182,10 @@ void MultiLayer<MatType>::Backward(
     // Initialize memory for the backward pass (if needed).
     InitializeBackwardPassMemory(input.n_cols);
 
-    network.back()->Backward(input, gy, layerDeltas.back());
+    network.back()->Backward(layerOutputs[network.size() - 2], gy, layerDeltas.back());
     for (size_t i = network.size() - 2; i > 0; --i)
-      network[i]->Backward(layerOutputs[i], layerDeltas[i + 1], layerDeltas[i]);
-    network[0]->Backward(layerOutputs[0], layerDeltas[1], g);
+      network[i]->Backward(layerOutputs[i-1], layerDeltas[i + 1], layerDeltas[i]);
+    network[0]->Backward(input, layerDeltas[1], g);
   }
   else if (network.size() == 1)
   {

Original file line number	Diff line number	Diff line change
`@@ -182,10 +182,10 @@ void MultiLayer<MatType>::Backward(`
`182`	`182`	`// Initialize memory for the backward pass (if needed).`
`183`	`183`	`InitializeBackwardPassMemory(input.n_cols);`
`184`	`184`
`185`		`- network.back()->Backward(input, gy, layerDeltas.back());`
	`185`	`+ network.back()->Backward(layerOutputs[network.size() - 2], gy, layerDeltas.back());`
`186`	`186`	`for (size_t i = network.size() - 2; i > 0; --i)`
`187`		`- network[i]->Backward(layerOutputs[i], layerDeltas[i + 1], layerDeltas[i]);`
`188`		`- network[0]->Backward(layerOutputs[0], layerDeltas[1], g);`
	`187`	`+ network[i]->Backward(layerOutputs[i-1], layerDeltas[i + 1], layerDeltas[i]);`
	`188`	`+ network[0]->Backward(input, layerDeltas[1], g);`
`189`	`189`	`}`
`190`	`190`	`else if (network.size() == 1)`
`191`	`191`	`{`