Refs #8913 Set exec count after algorithm is executed.

Otherwise LoadProcessNexus modifies the execution counter when it loads
histories from file and the parent algorithm gets the incorrect exec count.

As you should never need to set the exec count except in Algorithm, I've made
the method private and made Algorithm a friend class.

Code/Mantid/Framework/API/inc/MantidAPI/Algorithm.h

@@ -325,7 +325,7 @@ class MANTID_API_DLL Algorithm : public IAlgorithm, public Kernel::PropertyManag
   /// Set if an exception is thrown, and not caught, within a parallel region
   bool m_parallelException;
 
-  friend class WorkspaceHistory; // Allow workspace history loading to adjust g_execCount
+  friend class WorkspaceHistory; // Allow workspace history loading to adjust g_execCount 
   static size_t g_execCount; ///< Counter to keep track of algorithm execution order
 
   // ------------------ For WorkspaceGroups ------------------------------------

Code/Mantid/Framework/API/inc/MantidAPI/AlgorithmHistory.h

@@ -70,8 +70,6 @@ class MANTID_API_DLL AlgorithmHistory
 
   /// add a child algorithm history record to this history object
   void addChildHistory(const AlgorithmHistory& childHist);
-  /// set the duration time this algorithm history object
-  void setDuration(const double& duration);
   // get functions
   /// get name of algorithm in history const
   const std::string& name() const {return m_name;}
@@ -89,6 +87,8 @@ class MANTID_API_DLL AlgorithmHistory
   AlgorithmHistories getChildHistories() const { return m_childHistories; }
   /// Retrieve a child algorithm history by index
   const AlgorithmHistory & getChildAlgorithmHistory(const size_t index) const;
+    /// Add operator[] access
+  const AlgorithmHistory & operator[](const size_t index) const;
   /// Retrieve the number of child algorithms
   size_t childHistorySize() const;
   /// print contents of object
@@ -106,8 +106,14 @@ class MANTID_API_DLL AlgorithmHistory
   }
   /// Create a concrete algorithm based on a history record
   boost::shared_ptr<IAlgorithm> createAlgorithm() const;
+  // Allow Algorithm::execute to change the exec count & duration after the algorithm was executed
+  friend class Algorithm;
 
 private:
+  // Set the execution count 
+  void setExecCount(std::size_t execCount) { m_execCount = execCount; }
+  /// Set the duration time 
+  void setDuration(const double& duration) { m_executionDuration = duration; }
   /// The name of the Algorithm
   std::string m_name;
   /// The version of the algorithm

Code/Mantid/Framework/API/src/Algorithm.cpp

@@ -616,7 +616,7 @@ namespace Mantid
 
           start_time = Mantid::Kernel::DateAndTime::getCurrentTime();
           //populate history record before execution so we can record child algorithms in it
-          AlgorithmHistory algHist(this, start_time, -1.0, Algorithm::g_execCount);
+          AlgorithmHistory algHist(this, start_time);
           m_history = boost::make_shared<AlgorithmHistory>(algHist);
 
           // Start a timer
@@ -628,6 +628,7 @@ namespace Mantid
           // Get how long this algorithm took to run
           const float duration = timer.elapsed();
           m_history->setDuration(duration);
+          m_history->setExecCount(Algorithm::g_execCount);
 
           // need it to throw before trying to run fillhistory() on an algorithm which has failed
           if(trackingHistory())

Code/Mantid/Framework/API/src/AlgorithmHistory.cpp

@@ -30,7 +30,6 @@ AlgorithmHistory::AlgorithmHistory(const Algorithm* const alg, const Kernel::Dat
   }
 }
 
-
 /// Destructor
 AlgorithmHistory::~AlgorithmHistory()
 {}
@@ -122,12 +121,15 @@ const AlgorithmHistory & AlgorithmHistory::getChildAlgorithmHistory(const size_t
   return *start;
 }
 
-/** Set the duration time of the algorithm in the history
- *  @param duration :: The time the algorithm took to execute
+/**
+ * Index operator[] access to a child algorithm history
+ * @param index ::  An index within the algorithm history
+ * @returns A reference to a const AlgorithmHistory object
+ * @throws std::out_of_range error if the index is invalid
  */
-void AlgorithmHistory::setDuration(const double& duration)
+const AlgorithmHistory& AlgorithmHistory::operator[](const size_t index) const
 {
-  m_executionDuration = duration;
+  return getChildAlgorithmHistory(index);
 }
 
 /** Prints a text representation of itself