header for autograd engine

Author: Vansh5632

.gitignore

@@ -77,6 +77,7 @@ install_manifest.txt
 # Test artifacts
 Testing/
 googletest-*/
+test_tensor
 
 # Auto-generated files
 /include/config.h

include/core/autograd/function.h

@@ -0,0 +1,72 @@
+#pragma once
+#ifndef AUTOGRAD_FUNCTION_H
+#define AUTOGRAD_FUNCTION_H
+
+#include <memory>
+#include <string>
+#include <vector>
+
+#include "core/tensor/tensor.h"
+
+namespace torchscratch {
+namespace core {
+namespace autograd {
+class Variable;
+
+class Function {
+public:
+  virtual ~Function() = default;
+  Function() = default;
+  Function(const Function&) = default;
+  Function& operator=(const Function&) = default;
+  Function(Function&&) noexcept = default;
+  Function& operator=(Function&&) noexcept = default;
+
+  virtual std::vector<tensor::Tensor> forward(const std::vector<tensor::Tensor>& inputs) = 0;
+
+  virtual std::vector<tensor::Tensor> backward(const std::vector<tensor::Tensor>& grad_outputs) = 0;
+
+  virtual std::string name() const = 0;
+
+  void save_for_backward(const std::vector<tensor::Tensor>& inputs);
+
+  const std::vector<Variable*>& get_saved_variables() const;
+
+private:
+  std::vector<Variable*> saved_variables_;
+};
+class AddFunction:public Function{
+    public:
+        std::vector<tensor::Tensor> forward(const std::vector<tensor::Tensor>& inputs) override;
+        std::vector<tensor::Tensor> backward(const std::vector<tensor::Tensor>& grad_outputs) override;
+        std::string name() const override {
+            return "AddFunction";
+        }
+};
+class MulFunction:public Function{
+    public:
+        std::vector<tensor::Tensor> forward(const std::vector<tensor::Tensor>& inputs) override;
+        std::vector<tensor::Tensor> backward(const std::vector<tensor::Tensor>& grad_outputs) override;
+        std::string name() const override {
+            return "MulFunction";
+        }
+    private:
+        tensor::Tensor input1_;
+        tensor::Tensor input2_;
+};
+class MatMulFunction:public Function{
+    public:
+        std::vector<tensor::Tensor> forward(const std::vector<tensor::Tensor>& inputs) override;
+        std::vector<tensor::Tensor> backward(const std::vector<tensor::Tensor>& grad_outputs) override;
+        std::string name() const override {
+            return "MatMulFunction";
+        }
+    private:
+        tensor::Tensor input1_;
+        tensor::Tensor input2_;
+};
+
+}  // namespace autograd
+}  // namespace core
+}  // namespace torchscratch
+#endif