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// Copyright (c) 2006-2009 Max-Planck-Institute Saarbruecken (Germany).
// All rights reserved.
//
// This file is part of CGAL (www.cgal.org)
//
// $URL: https://github.com/CGAL/cgal/blob/v6.1/Algebraic_kernel_d/include/CGAL/Algebraic_kernel_d/Shear_controller.h $
// $Id: include/CGAL/Algebraic_kernel_d/Shear_controller.h b26b07a1242 $
// SPDX-License-Identifier: LGPL-3.0-or-later OR LicenseRef-Commercial
//
//
// Author(s) : Michael Kerber <mkerber@mpi-inf.mpg.de>
//
// ============================================================================
#ifndef CGAL_ACK_SHEAR_CONTROLLER
#define CGAL_ACK_SHEAR_CONTROLLER 1
#include <CGAL/disable_warnings.h>
#include <CGAL/basic.h>
#include <CGAL/Random.h>
#include <CGAL/tss.h>
#include<set>
namespace CGAL {
namespace internal {
/*!
* \brief A class that controls the used shear factors
*
* The objects returns positive integers that are used as shear factors.
* It choses integers from the range \c 1..max at random ,
* where \c c is a positive integer
* initially set in the constructor (8 by default). No integer is given
* twice by \c get_shear_factor(), at least if the failed ones are reported
* with the \c report_failure() method.
* If more than half of the integers in the range were bad, the range is
* enlarged to \c 1..2*max.
*/
template<typename Int,int InitialMax=8>
class Shear_controller {
public:
//! Constructor, getting the maximal absolute value of the shear factor
Shear_controller()
:
#if CGAL_ACK_STATIC_SEED
#warning Warning, uses static seed!
rng(CGAL_ACK_STATIC_SEED)
#else
rng()
#endif
, m_max(InitialMax)
, pos_next_factor(0) {
CGAL_assertion(m_max>=1);
}
//! Reports that the shear factor \c factor was bad.
void report_failure(Int factor) {
this->bad_shears.insert(factor);
long failures=static_cast<long>(this->bad_shears.size())+1;
if(2*failures>this->m_max) {
this->m_max*=2;
}
}
//! Gets a shear factor
Int get_shear_factor() {
if(pos_next_factor==static_cast<int>(value_order().size())) {
value_order().push_back(get_new_shear_factor());
}
return value_order()[pos_next_factor++];
}
private:
//! Gets a new shear factor
Int get_new_shear_factor() {
CGAL_assertion(int(this->bad_shears.size())<m_max);
while(true) {
Int s = Int((rng.get_int(0,(std::numeric_limits<int>::max)())%m_max )+1);
if(bad_shears.find(s)==bad_shears.end()) {
return s;
}
}
}
Random rng;
// Maximal absolute value
Int m_max;
static std::vector<Int>& value_order() {
CGAL_STATIC_THREAD_LOCAL_VARIABLE_0(std::vector<Int>, value_order_);
return value_order_;
}
int pos_next_factor;
// Unsuccessful shear factors
std::set<Int> bad_shears;
};
} // namespace internal
} //namespace CGAL
#include <CGAL/enable_warnings.h>
#endif // CGAL_ACK_SHEAR_CONTROLLER
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