Merge branch 'Fix_loss_derivative' into 'dev'

Fix loss derivative

See merge request !43

src/loss/classification/BCE.cpp

@@ -123,7 +123,7 @@ Aidge::Tensor Aidge::loss::BCE(std::shared_ptr<Tensor>& prediction,
     // Define node: gradient
     const std::shared_ptr<Node> gradient_node = Mul("gradient");
     div1_node->addChild(gradient_node, 0, 0);
-    Producer(std::make_shared<Tensor>(Array1D<float, 1>{{-1.0f/float(target->dims()[0])}}))
+    Producer(std::make_shared<Tensor>(Array1D<float, 1>{{-1.0f/float(target->size())}}))
         ->addChild(gradient_node, 0, 1);
 
     // Create GraphView

src/loss/regression/MSE.cpp

@@ -83,7 +83,7 @@ Aidge::Tensor Aidge::loss::MSE(std::shared_ptr<Tensor>& prediction,
 
     // Note: this assume target is [nbBatch, nbChan]
     Producer(std::make_shared<Tensor>(
-                 Array1D<float, 1>{{2 / float(target->dims()[0])}}))
+                 Array1D<float, 1>{{2 / float(target->size())}}))
         ->addChild(mul_node, 0, 1);
     sub_node->addChild(mul_node, 0, 0);  // Error computation branch !