//# Copyright (C) 2000,2001
//# Associated Universities, Inc. Washington DC, USA.
//#
//# This library is free software; you can redistribute it and/or modify it
//# under the terms of the GNU Library General Public License as published by
//# the Free Software Foundation; either version 2 of the License, or (at your
//# option) any later version.
//#
//# This library is distributed in the hope that it will be useful, but WITHOUT
//# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
//# FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Library General Public
//# License for more details.
//#
//# You should have received a copy of the GNU Library General Public License
//# along with this library; if not, write to the Free Software Foundation,
//# Inc., 675 Massachusetts Ave, Cambridge, MA 02139, USA.
//#
//# Correspondence concerning AIPS++ should be addressed as follows:
//#        Internet email: casa-feedback@nrao.edu.
//#        Postal address: AIPS++ Project Office
//#                        National Radio Astronomy Observatory
//#                        520 Edgemont Road
//#                        Charlottesville, VA 22903-2475 USA

#ifndef SCIMATH_ZSCORECALCULATOR_H
#define SCIMATH_ZSCORECALCULATOR_H

#include <casacore/casa/aips.h>

#include <cmath>
#include <map>
#include <mutex>
#include <set>

namespace casacore {

class Mutex;

// This class contains static methods related to z-scores. A z-score is the
// number of standard deviations from the mean in a normal distribution.

class ZScoreCalculator {
public:

    ZScoreCalculator() = delete;

    // compute the maximum expected zscore given the number of points
    // in a sample.
    static Double getMaxZScore(uInt64 npts);

    // Get the minimum number of points in a Gaussian distribution, such that
    // the probability that the maximum of the distribution having the specified
    // zscore is 0.5. <src>zscore</src> should be non-negative.
    static inline uInt64 zscoreToNpts(Double zscore) {
        return (uInt64)(0.5/erfc(zscore/sqrt(2)));
    }

private:
    static std::map<uInt64, Double> _nptsToMaxZScore;
    static std::mutex _mutex;

};

}

#endif
