Implement custom Shape struct with __device__ support

include/shape.hpp

@@ -1,11 +1,71 @@
 #pragma once
 
+#ifndef __host__
+#define __host__
+#endif
+
+#ifndef __device__
+#define __device__
+#endif
+
 #include <format>
 #include <vector>
 
 namespace CUDANet {
 
-typedef std::vector<size_t> Shape;
+struct Shape {
+    static constexpr size_t MAX_DIMS = 8;
+    
+    size_t dims[MAX_DIMS];
+    size_t ndim;
+    
+    __host__ __device__ Shape() : ndim(0) {
+        for (int i = 0; i < MAX_DIMS; i++) dims[i] = 0;
+    }
+    
+    __host__ Shape(std::initializer_list<size_t> list) : ndim(list.size()) {
+        if (ndim > MAX_DIMS) {
+            throw std::runtime_error("Too many dimensions");
+        }
+        size_t i = 0;
+        for (auto val : list) {
+            dims[i++] = val;
+        }
+        for (; i < MAX_DIMS; i++) dims[i] = 0;
+    }
+    
+    __host__ Shape(const std::vector<size_t>& vec) : ndim(vec.size()) {
+        if (ndim > MAX_DIMS) {
+            throw std::runtime_error("Too many dimensions");
+        }
+        for (size_t i = 0; i < ndim; i++) {
+            dims[i] = vec[i];
+        }
+        for (size_t i = ndim; i < MAX_DIMS; i++) dims[i] = 0;
+    }
+    
+    __host__ __device__ size_t operator[](size_t idx) const {
+        return dims[idx];
+    }
+    
+    __host__ __device__ size_t& operator[](size_t idx) {
+        return dims[idx];
+    }
+    
+    __host__ __device__ size_t size() const { return ndim; }
+    
+    __host__ bool operator==(const Shape& other) const {
+        if (ndim != other.ndim) return false;
+        for (size_t i = 0; i < ndim; i++) {
+            if (dims[i] != other.dims[i]) return false;
+        }
+        return true;
+    }
+    
+    __host__ bool operator!=(const Shape& other) const {
+        return !(*this == other);
+    }
+};
 
 std::string format_shape(const Shape& shape) {
     std::string result;