Add default dtype to backend

include/backend.hpp

@@ -1,8 +1,10 @@
 #pragma once
 
 #include <memory>
+#include <optional>
 
 #include "shape.hpp"
+#include "tensor.hpp"
 
 namespace CUDANet {
 
@@ -22,7 +24,14 @@ class BackendFactory {
 };
 
 class Backend {
+  protected:
+    std::optional<DType> default_dtype;
   public:
+
+    virtual bool supports_dtype(DType dtype) const = 0;
+    virtual void set_default_dtype(DType dtype) = 0;
+    virtual DType get_default_dtype() const = 0;
+
     // Memory management
     virtual void* allocate(size_t bytes) = 0;
     virtual void  deallocate(void* ptr)  = 0;

include/backend/cuda/cuda.cuh

@@ -1,6 +1,7 @@
 #pragma once
 
 #include <cstdio>
+#include <set>
 
 #include "backend.hpp"
 #include "tensor.hpp"
@@ -29,9 +30,14 @@ namespace CUDANet::Backends {
 class CUDA : public Backend {
   private:
     int device_id;
+    std::set<DType> supported_dtypes;
   public:
     CUDA(const BackendConfig& config);
 
+    bool supports_dtype(DType dtype) const override;
+    void set_default_dtype(DType dtype) override;
+    DType get_default_dtype() const override;
+
     static bool is_cuda_available();
     void initialize();
 

include/shape.hpp

@@ -66,6 +66,12 @@ struct Shape {
     __host__ bool operator!=(const Shape& other) const {
         return !(*this == other);
     }
+
+    __host__ __device__ bool empty() const {
+        return ndim == 0;
+    }
+
+
 };
 
 std::string format_shape(const Shape& shape) {

include/tensor.hpp

@@ -16,11 +16,14 @@ enum class DType
     // INT32,  // Not implemented yet
 };
 
+size_t dtype_size(DType dtype);
+
 class Tensor
 {
 public:
 
     Tensor() = default;
+    Tensor(Shape shape, CUDANet::Backend* backend);
     Tensor(Shape shape, DType dtype, CUDANet::Backend* backend);
 
     Tensor(Tensor&& other) noexcept;
@@ -30,6 +33,8 @@ public:
 
     ~Tensor();
 
+    DType get_dtype();
+
     size_t size() const;
     size_t numel() const;