Fix some compilation errors

src/backends/cuda/cuda_backend.cu

@@ -25,7 +25,7 @@ cudaDeviceProp initializeCUDA() {
     return deviceProp;
 }
 
-using namespace CUDANet::Backend;
+using namespace CUDANet::Backends;
 
 void* CUDA::allocate(size_t bytes) {
     void* d_ptr = nullptr;

src/backends/cuda/kernels/activation_functions.cu

@@ -1,5 +1,4 @@
 #include "activation_functions.cuh"
-#include "cuda_helper.cuh"
 
 using namespace CUDANet;
 

src/backends/cuda/kernels/matmul.cu

@@ -1,4 +1,4 @@
-#include "cuda_helper.cuh"
+#include "backend/cuda.cuh"
 #include "matmul.cuh"
 
 using namespace CUDANet;

src/backends/cuda/layer_ops.cu

@@ -4,7 +4,7 @@
 #include "kernels/matmul.cuh"
 #include "kernels/pool.cuh"
 
-using namespace CUDANet::Backend;
+using namespace CUDANet::Backends;
 
 void CUDA::relu(Tensor& tensor) {
     int gridSize = (tensor.numel() + BLOCK_SIZE - 1) / BLOCK_SIZE;

src/backends/cuda/tensor_ops.cu

@@ -4,7 +4,7 @@
 #include "backend/cuda.cuh"
 #include "kernels/matmul.cuh"
 
-using namespace CUDANet::Backend;
+using namespace CUDANet::Backends;
 
 void CUDA::print(const CUDANet::Tensor &input) {
     auto length = input.numel();

src/layers/activation.cpp

@@ -7,11 +7,11 @@
 
 using namespace CUDANet::Layers;
 
-Activation::Activation(CUDANet::Backend* backend, ActivationType activation, const CUDANet::Shape &shape)
+Activation::Activation(ActivationType activation, const CUDANet::Shape &shape, CUDANet::Backend* backend)
     : backend(backend), activationType(activation), shape(shape) {
 
     if (shape.size() != 1) {
-        throw std::runtime_error(std::format("Invalid shape. Expected [1], got {}", shape));
+        throw InvalidShapeException("input", 1, shape.size());
     }
 
     auto length = shape[0];