kahan_accumulator.hpp

// FEAT3: Finite Element Analysis Toolbox, Version 3
// Copyright (C) 2010 by Stefan Turek & the FEAT group
// FEAT3 is released under the GNU General Public License version 3,
// see the file 'copyright.txt' in the top level directory for details.
 
#pragma once
 
namespace FEAT
{
  template<typename DT_>
  class KahanAccumulator
  {
  public:
    DT_ value;
    DT_ correction;
 
    KahanAccumulator() :
      value(DT_(0)),
      correction(DT_(0))
    {
    }
 
    explicit KahanAccumulator(DT_ val) :
      value(val),
      correction(DT_(0))
    {
    }
 
    void clear()
    {
      value = correction = DT_(0);
    }
 
    KahanAccumulator& operator+=(DT_ val)
    {
      DT_ y = val - this->correction;
      DT_ t = this->value + y;
      this->correction = (t - this->value) - y;
      this->value = t;
      return *this;
    }
 
    operator DT_() const
    {
      return value;
    }
  }; // class KahanAccumulator<...>
} // namespace FEAT