// $Id: CrossValidationSampler.cc 1392 2008-07-28 19:35:30Z peter $

/*
	Copyright (C) 2006, 2007 Jari Häkkinen, Peter Johansson
	Copyright (C) 2008 Peter Johansson

	This file is part of the yat library, http://dev.thep.lu.se/yat

	The yat library is free software; you can redistribute it and/or
	modify it under the terms of the GNU General Public License as
	published by the Free Software Foundation; either version 2 of the
	License, or (at your option) any later version.

	The yat 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
	General Public License for more details.

	You should have received a copy of the GNU General Public License
	along with this program; if not, write to the Free Software
	Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
	02111-1307, USA.
*/

#include "CrossValidationSampler.h"
#include "Target.h"
#include "yat/random/random.h"

#include <algorithm>
#include <cassert>
#include <utility>
#include <vector>

namespace theplu {
namespace yat {
namespace classifier {  

	CrossValidationSampler::CrossValidationSampler(const Target& target, 
																								 const size_t N, 
																								 const size_t k)
		: Sampler(target, N), k_(k)
	{	
		assert(target.size()>1);
		build(target, N, k);
	}

	CrossValidationSampler::~CrossValidationSampler()
	{
	}

	void CrossValidationSampler::build(const Target& target, size_t N, size_t k)
	{
		std::vector<std::pair<size_t,size_t> > v;
		for (size_t i=0; i<target.size(); i++)
			v.push_back(std::make_pair(target(i),i));
		// sorting with respect to class
		std::sort(v.begin(),v.end());
		
		// my_begin[i] is index of first sample of class i
		std::vector<size_t> my_begin;
		my_begin.reserve(target.nof_classes());
		my_begin.push_back(0);
		for (size_t i=1; i<target.size(); i++)
			while (v[i].first > my_begin.size()-1)
				my_begin.push_back(i);
		my_begin.push_back(target.size());

		for (size_t i=0; i<N; ) {
			// shuffle indices within class each class
			for (size_t j=0; j+1<my_begin.size(); ++j)
				random::random_shuffle(v.begin()+my_begin[j],v.begin()+my_begin[j+1]);
			
			for (size_t part=0; part<k && i<N; i++, part++) {
				std::vector<size_t> training_index;
				std::vector<size_t> validation_index;
				for (size_t j=0; j<v.size(); j++) {
					if (j%k==part)
						validation_index.push_back(v[j].second);
					else
						training_index.push_back(v[j].second);
				}

				training_index_.push_back(utility::Index(training_index));
				validation_index_.push_back(utility::Index(validation_index));
			}
		}
		assert(training_index_.size()==N);
		assert(validation_index_.size()==N);
		
		for (size_t i=0; i<N; ++i){
			training_target_.push_back(Target(target,training_index_[i]));
			validation_target_.push_back(Target(target,validation_index_[i]));
		}
		assert(training_target_.size()==N);
		assert(validation_target_.size()==N);
	}

}}} // of namespace classifier, yat, and theplu