SearchMin.hpp
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/****************************************************************************
*
* Copyright (c) 2018 PX4 Development Team. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
* 3. Neither the name PX4 nor the names of its contributors may be
* used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*
****************************************************************************/
/**
* @file Seach.hpp
*
* - Binary Search (ToDo)
* - Golden Section Search
*/
#pragma once
namespace math
{
static constexpr double GOLDEN_RATIO = 1.6180339887; //(sqrt(5)+1)/2
// Type-safe abs
template<typename _Tp>
_Tp abs_t(_Tp val)
{
return ((val > (_Tp)0) ? val : -val);
}
// golden section search to find extremeum for function with minimum
template<typename _Tp>
inline const _Tp goldensection(const _Tp &arg1, const _Tp &arg2, _Tp(*fun)(_Tp), const _Tp &tol)
{
_Tp a = arg1;
_Tp b = arg2;
_Tp c = b - (b - a) / GOLDEN_RATIO;
_Tp d = a + (b - a) / GOLDEN_RATIO;
while (abs_t(c - d) > tol) {
if (fun(c) < fun(d)) {
b = d;
} else {
a = c;
}
c = b - (b - a) / GOLDEN_RATIO;
d = a + (b - a) / GOLDEN_RATIO;
}
return ((b + a) / (_Tp)2);
}
}