/*

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.

 *

 * This code 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 General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 *

 */

#include "utilities/numberSeq.hpp"

// Utility class containing various helper methods for prediction.

class G1Predictions {

 private:

  double _sigma;

  // This function is used to estimate the stddev of sample sets. There is some

  // special consideration of small sample sets: the actual stddev for them is

  // not very useful, so we calculate some value based on the sample average.

  // Five or more samples yields zero (at that point we use the stddev); fewer

  // scale the sample set average linearly from two times the average to 0.5 times

  // it.

  double stddev_estimate(TruncatedSeq const* seq) const {

    double estimate = seq->dsd();

    int const samples = seq->num();

    if (samples < 5) {

      estimate = MAX2(seq->davg() * (5 - samples) / 2.0, estimate);

    }

    return estimate;

  }

 public:

  G1Predictions(double sigma) : _sigma(sigma) {

    assert(sigma >= 0.0, "Confidence must be larger than or equal to zero");

  }

  // Confidence factor.

  double sigma() const { return _sigma; }

  double get_new_prediction(TruncatedSeq const* seq) const {

    return seq->davg() + _sigma * stddev_estimate(seq);

  }

};