CondFormats/Calibration/interface/TensorIndex.h - master - githubmirror/cmssw

CondFormats/Calibration/interface/TensorIndex.h

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29 май 2019, 08:24

29 май 2019, 08:245c96c3b

#ifndef TensorIndex_h
#define TensorIndex_h
///
///Credit:
///Utility class from
///
///http://www.sitmo.com/doc/A_Simple_and_Extremely_Fast_CPP_Template_for_Matrices_and_Tensors
///
///Usage:
///
///The template below offers a simple and efficient solution for handling matrices and tensors in C++. The idea is to store the matrix (or tensor) in a standard vector by translating the multidimensional index to a one dimensional index.
///
///The only thing we need to do is to convert two dimensional indices (r,c) into a one dimensional index. Using template we can do this very efficiently compile time, minimizing the runtime overhead.
///
template <int d1, int d2 = 1, int d3 = 1, int d4 = 1>
class TensorIndex {
public:
  enum { SIZE = d1 * d2 * d3 * d4 };
  enum { LEN1 = d1 };
  enum { LEN2 = d2 };
  enum { LEN3 = d3 };
  enum { LEN4 = d4 };

  static int indexOf(const int i) { return i; }
  static int indexOf(const int i, const int j) { return j * d1 + i; }
  static int indexOf(const int i, const int j, const int k) { return (k * d2 + j) * d1 + i; }
  static int indexOf(const int i, const int j, const int k, const int l) { return ((l * d3 + k) * d2 + j) * d1 + i; }
};

template <int d1, int d2 = 1, int d3 = 1, int d4 = 1>
class TensorIndex_base1 {
public:
  enum { SIZE = d1 * d2 * d3 * d4 };
  enum { LEN1 = d1 };
  enum { LEN2 = d2 };
  enum { LEN3 = d3 };
  enum { LEN4 = d4 };

  static int indexOf(const int i) { return i - 1; }
  static int indexOf(const int i, const int j) { return j * d1 + i - 1 - d1; }
  static int indexOf(const int i, const int j, const int k) { return (k * d2 + j) * d1 + i - 1 - d1 - d1 * d2; }
  static int indexOf(const int i, const int j, const int k, const int l) {
    return ((l * d3 + k) * d2 + j) * d1 + i - 1 - d1 - d1 * d2 - d1 * d2 * d3;
  }
};
#endif