simple_base_change.h

// ---------------------------------------------------------------------------
//
//  This file is part of PermLib.
//
// Copyright (c) 2009-2011 Thomas Rehn <thomas@carmen76.de>
// 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. The name of the author may not be used to endorse or promote products
//    derived from this software without specific prior written permission.
// 
// THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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// OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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// NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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// ---------------------------------------------------------------------------
 
 
#ifndef SIMPLEBASECHANGE_H_
#define SIMPLEBASECHANGE_H_
 
#include <permlib/change/base_change.h>
 
namespace permlib {

template<class PERM, class TRANS, class BASETRANSPOSE>
class SimpleBaseChange : public BaseChange<PERM,TRANS> {
public:
        explicit SimpleBaseChange(const BSGS<PERM,TRANS>&);
        
    template <class InputIterator>
    void change(BSGS<PERM,TRANS> &bsgs, InputIterator baseBegin, InputIterator baseEnd, bool skipRedundant = false) const;
};
 
//
//     ----       IMPLEMENTATION
//
 
template<class PERM, class TRANS, class BASETRANSPOSE>
SimpleBaseChange<PERM,TRANS,BASETRANSPOSE>::SimpleBaseChange(const BSGS<PERM,TRANS>&) 
        : BaseChange<PERM,TRANS>() 
{ }
 
template<class PERM, class TRANS, class BASETRANSPOSE>
template<class InputIterator>
void SimpleBaseChange<PERM,TRANS,BASETRANSPOSE>::change(BSGS<PERM,TRANS> &bsgs, InputIterator baseBegin, InputIterator baseEnd, bool skipRedundant) const {
        if (baseBegin == baseEnd)
                return;
 
        const unsigned long origOrder __attribute__((unused)) = bsgs.order();
        BASETRANSPOSE trans;
        
        unsigned int baseTargetPos = 0;
    while (baseBegin != baseEnd && baseTargetPos < bsgs.B.size()) {
                unsigned long alpha = *baseBegin;
                unsigned long beta = bsgs.B[baseTargetPos];
                const bool redundant = skipRedundant && this->isRedundant(bsgs, baseTargetPos, alpha);
                
                if (!redundant && beta != alpha) {
                        unsigned int pos = bsgs.insertRedundantBasePoint(alpha);
                        for (; pos > baseTargetPos; --pos) {
                                trans.transpose(bsgs, pos-1);
                                ++BaseChange<PERM,TRANS>::m_statTranspositions;
                        }
                }
                
                ++baseBegin;
                if (!redundant)
                        ++baseTargetPos;
    }
        // insert remaining base points
        while (!skipRedundant && baseBegin != baseEnd) {
                const unsigned long alpha = *baseBegin;
                bsgs.insertRedundantBasePoint(alpha, baseTargetPos);
                
                ++baseBegin;
                ++baseTargetPos;
        }
        
        bsgs.stripRedundantBasePoints(baseTargetPos);
        BaseChange<PERM,TRANS>::m_statScheierGeneratorsConsidered += trans.m_statScheierGeneratorsConsidered;
        
        BOOST_ASSERT(origOrder == bsgs.order());
}
 
}
 
#endif // -- SIMPLEBASECHANGE_H_