Added support for argmax/argmin

unsupported/Eigen/CXX11/src/Tensor/TensorMeta.h

@@ -31,6 +31,60 @@ template <> struct max_n_1<0> {
   static const size_t size = 1;
 };
 
+
+
+
+#if defined(EIGEN_HAS_CONSTEXPR)
+#define EIGEN_CONSTEXPR constexpr
+#else
+#define EIGEN_CONSTEXPR
+#endif
+
+// Tuple mimics std::pair but works on e.g. nvcc.
+template <typename U, typename V> struct Tuple {
+ public:
+  U first;
+  V second;
+
+  typedef U first_type;
+  typedef V second_type;
+
+  EIGEN_CONSTEXPR EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE
+  Tuple() : first(), second() {}
+
+  EIGEN_CONSTEXPR EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE
+  Tuple(const U& f, const V& s) : first(f), second(s) {}
+
+  EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE
+  Tuple& operator= (const Tuple& rhs) {
+    if (&rhs == this) return *this;
+    first = rhs.first;
+    second = rhs.second;
+    return *this;
+  }
+
+  EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE
+  void swap(Tuple& rhs) {
+    using numext::swap;
+    swap(first, rhs.first);
+    swap(second, rhs.second);
+  }
+};
+
+template <typename U, typename V>
+EIGEN_CONSTEXPR EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE
+bool operator==(const Tuple<U, V>& x, const Tuple<U, V>& y) {
+  return (x.first == y.first && x.second == y.second);
+}
+
+template <typename U, typename V>
+EIGEN_CONSTEXPR EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE
+bool operator!=(const Tuple<U, V>& x, const Tuple<U, V>& y) {
+  return !(x == y);
+}
+
+#undef EIGEN_CONSTEXPR
+
 }  // namespace Eigen
 
 #endif  // EIGEN_CXX11_TENSOR_TENSOR_META_H