More utility in autograd.

src/learn/autograd.h

@@ -7,6 +7,44 @@
 #include <memory>
 #include <tuple>
 
+namespace Learner
+{
+    template <typename T>
+    struct ValueWithGrad
+    {
+        T value;
+        T grad;
+
+        ValueWithGrad& operator+=(const ValueWithGrad<T>& rhs)
+        {
+            value += rhs.value;
+            grad += rhs.grad;
+            return *this;
+        }
+
+        ValueWithGrad& operator-=(const ValueWithGrad<T>& rhs)
+        {
+            value -= rhs.value;
+            grad -= rhs.grad;
+            return *this;
+        }
+
+        ValueWithGrad& operator*=(T rhs)
+        {
+            value *= rhs;
+            grad *= rhs;
+            return *this;
+        }
+
+        ValueWithGrad& operator/=(T rhs)
+        {
+            value /= rhs;
+            grad /= rhs;
+            return *this;
+        }
+    };
+}
+
 namespace Learner::Autograd::UnivariateStatic
 {
 
@@ -19,8 +57,20 @@ namespace Learner::Autograd::UnivariateStatic
     template <typename T>
     using Id = typename Identity<T>::type;
 
+    template <typename T>
+    struct Evaluable
+    {
+        template <typename... ArgsTs>
+        auto eval(const std::tuple<ArgsTs...>& args) const
+        {
+            using ValueType = typename T::ValueType;
+            const T* this_ = static_cast<const T*>(this);
+            return ValueWithGrad<ValueType>{ this_->value(args), this_->grad(args) };
+        }
+    };
+
     template <typename T, int I>
-    struct VariableParameter
+    struct VariableParameter : Evaluable<VariableParameter<T, I>>
     {
         using ValueType = T;
 
@@ -42,7 +92,7 @@ namespace Learner::Autograd::UnivariateStatic
     };
 
     template <typename T, int I>
-    struct ConstantParameter
+    struct ConstantParameter : Evaluable<ConstantParameter<T, I>>
     {
         using ValueType = T;
 
@@ -64,7 +114,7 @@ namespace Learner::Autograd::UnivariateStatic
     };
 
     template <typename T>
-    struct Constant
+    struct Constant : Evaluable<Constant<T>>
     {
         using ValueType = T;
 
@@ -90,7 +140,7 @@ namespace Learner::Autograd::UnivariateStatic
     };
 
     template <typename LhsT, typename RhsT, typename T = typename LhsT::ValueType>
-    struct Sum
+    struct Sum : Evaluable<Sum<LhsT, RhsT, T>>
     {
         using ValueType = T;
 
@@ -136,7 +186,7 @@ namespace Learner::Autograd::UnivariateStatic
     }
 
     template <typename LhsT, typename RhsT, typename T = typename LhsT::ValueType>
-    struct Difference
+    struct Difference : Evaluable<Difference<LhsT, RhsT, T>>
     {
         using ValueType = T;
 
@@ -182,7 +232,7 @@ namespace Learner::Autograd::UnivariateStatic
     }
 
     template <typename LhsT, typename RhsT, typename T = typename LhsT::ValueType>
-    struct Product
+    struct Product : Evaluable<Product<LhsT, RhsT, T>>
     {
         using ValueType = T;
 
@@ -228,7 +278,7 @@ namespace Learner::Autograd::UnivariateStatic
     }
 
     template <typename ArgT, typename T = typename ArgT::ValueType>
-    struct Sigmoid
+    struct Sigmoid : Evaluable<Sigmoid<ArgT, T>>
     {
         using ValueType = T;
 
@@ -270,7 +320,7 @@ namespace Learner::Autograd::UnivariateStatic
     }
 
     template <typename ArgT, typename T = typename ArgT::ValueType>
-    struct Pow
+    struct Pow : Evaluable<Pow<ArgT, T>>
     {
         using ValueType = T;
 
@@ -304,7 +354,7 @@ namespace Learner::Autograd::UnivariateStatic
     }
 
     template <typename ArgT, typename T = typename ArgT::ValueType>
-    struct Log
+    struct Log : Evaluable<Log<ArgT, T>>
     {
         using ValueType = T;