Fix backward pass in FCImpl CPU kernel

Add debug logging to Heaviside implementation forward pass

include/aidge/backend/cpu/operator/FCImpl_kernels.hpp

@@ -167,7 +167,7 @@ void FCImpl_cpu_backward_kernel(const DimSize_t batchSize,
             for (std::size_t o = 0; o < outputFeatureSize; ++o) {
                 sum += weight[o*inputFeatureSize + c] * input[b*outputFeatureSize + o];
             }
-            output[b*inputFeatureSize + c]+= sum;
+            output[b*inputFeatureSize + c] = sum;
         }
     }
 }

src/operator/HeavisideImpl.cpp

@@ -26,6 +26,8 @@ template <> void Aidge::HeavisideImplCpu::forward() {
   const auto impl =
       Registrar<HeavisideImplCpu>::create(getBestMatch(getRequiredSpec()));
 
+  Log::info("(HeavisideImpl.cpp) Before forward");
+  Log::info("(HeavisideImpl.cpp) Input 0 \n{}", input0->toString());
   impl.forward(input0->size(), getCPUPtr(mOp.getRawInput(0)),
                getCPUPtr(mOp.getRawOutput(0)), op_.value());
 }