TPC code discussions

Notes on TPC Digitization

General recommendations

• write small functions inline in header
  • description: The problem is that the compiler cannot inline small functions even from within the same file, if they are part of the (visible) interface of Digitizer
  • one could also consider not making some functions part of interface (and not make them link-visible)
• do not return vector<T> from functions (return vector<T> & or modify a vector passed by reference to a function)
• do not allocate new vector<T> containers at each step
• favour reusing/reseting containers over deleting/recreating
• avoid divisions by constants (often better to define inverse constant and multiply)
• avoid dynamic casting when reading from a TClonesArray (we should make this better by introducing a strongly typed TClonesArray extension)
• use const keyword wherever possible
  • variable that do not change
  • functions which do not change member variables
  • invariant arguments
    • note that const functions require the const keyword after the function: foo() const;
• consistently use C++11 range based iteration (much less code):
  • for(auto &hit : mHits)
• avoid division by constants (or constant member variables) in favour of multiplications with cached inverses
• We need to address the question of storage in std::vector
  • std::vector<Hits*> might be very bad (looses all the good stuff of TClonesArray) and leads to many small memory allocations
  • std::vector<Hits> might be ok if we use emplace_back and move semantics

Questions:

• does mixing Float_t and Double_t make sense? (example: getTime function
  • this is potentially bad for vectorization
• getPadResponse does not seem to be doing anything with its arguments