Add BeginUseAdjoints and EndUseAdjoints.

Author: jblueh

Common/include/basic_types/ad_structure.hpp

@@ -78,6 +78,19 @@ inline void RegisterOutput(su2double& data) {}
  */
 inline void ResizeAdjoints() {}
 
+/*!
+ * \brief Declare that the adjoints are being used, to protect against resizing.
+ *
+ * Should be used together with AD::EndUseAdjoints() to protect AD::SetDerivative() and AD::GetDerivative() calls,
+ * multiple at once if possible.
+ */
+inline void BeginUseAdjoints() {}
+
+/*!
+ * \brief Declare that the adjoints are no longer being used.
+ */
+inline void EndUseAdjoints() {}
+
 /*!
  * \brief Sets the adjoint value at index to val
  * \param[in] index - Position in the adjoint vector.
@@ -375,6 +388,10 @@ FORCEINLINE void Reset() {
 
 FORCEINLINE void ResizeAdjoints() { AD::getTape().resizeAdjointVector(); }
 
+FORCEINLINE void BeginUseAdjoints() { AD::getTape().beginUseAdjointVector(); }
+
+FORCEINLINE void EndUseAdjoints() { AD::getTape().beginUseAdjointVector(); }
+
 FORCEINLINE void SetIndex(int& index, const su2double& data) { index = data.getIdentifier(); }
 
 // WARNING: For performance reasons, this method does not perform bounds checking.