CurvilinearTrajectoryError.h

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#ifndef _TRACKER_CURVILINEARTRAJECTORYERROR_H_
#define _TRACKER_CURVILINEARTRAJECTORYERROR_H_

#include "DataFormats/GeometrySurface/interface/TrivialError.h"
#include "DataFormats/Math/interface/AlgebraicROOTObjects.h"
#include "DataFormats/Math/interface/Error.h"

class CurvilinearTrajectoryError {
public:
  enum { dimension = 5 };
  typedef math::Error<dimension>::type MathCovarianceMatrix;

  // construct
  CurvilinearTrajectoryError() {}

  CurvilinearTrajectoryError(InvalidError) : theCovarianceMatrix(ROOT::Math::SMatrixNoInit()) {
    theCovarianceMatrix(0, 0) = -99999.e10;
  }

  CurvilinearTrajectoryError(const AlgebraicSymMatrix55 &aCovarianceMatrix) : theCovarianceMatrix(aCovarianceMatrix) {}
  template <typename M55>
  CurvilinearTrajectoryError(const M55 &aCovarianceMatrix) : theCovarianceMatrix(aCovarianceMatrix) {}

  bool invalid() const { return theCovarianceMatrix(0, 0) < -1.e10; }
  bool valid() const { return !invalid(); }

  // not really full check of posdef
  bool posDef() const {
    return (theCovarianceMatrix(0, 0) >= 0) && (theCovarianceMatrix(1, 1) >= 0) && (theCovarianceMatrix(2, 2) >= 0) &&
           (theCovarianceMatrix(3, 3) >= 0) && (theCovarianceMatrix(4, 4) >= 0);
  }

  // access

  const AlgebraicSymMatrix55 &matrix() const { return theCovarianceMatrix; }

  AlgebraicSymMatrix55 &matrix() { return theCovarianceMatrix; }

  void operator*=(double factor) { theCovarianceMatrix *= factor; }

  void zeroFieldScaling(double factor) {
    double root_of_factor = sqrt(factor);
    //scale the 0 indexed covariance by the factor
    for (unsigned int i = 1; i != 5; ++i)
      theCovarianceMatrix(i, 0) *= root_of_factor;

    //scale all others by the scared factor
    for (unsigned int i = 1; i != 5; ++i)
      for (unsigned int j = i; j != 5; ++j)
        theCovarianceMatrix(i, j) *= factor;
    //term 0,0 is not scaled at all
  }

  operator MathCovarianceMatrix &() { return theCovarianceMatrix; }
  operator const MathCovarianceMatrix &() const { return theCovarianceMatrix; }

private:
  AlgebraicSymMatrix55 theCovarianceMatrix;
};

#endif