gstabsearch.cpp

来自「一个由Mike Gashler完成的机器学习方面的includes neural」· C++ 代码 · 共 120 行

#include "GStabSearch.h"
#include "GBits.h"
#include <math.h>
#include <stdio.h>

GStabSearch::GStabSearch(GRealVectorCritic* pCritic, double dMin, double dRange)
: GRealVectorSearch(pCritic)
{
	m_dMin = dMin;
	m_dRange = dRange;
	m_dTolerance = .00001;
	m_nDimensions = pCritic->GetVectorSize();
	m_pMins = new double[m_nDimensions];
	m_pRanges = new double[m_nDimensions];
	m_pVector = new double[m_nDimensions];
	m_nMask[0] = 0;
	m_nMask[1] = 0;
	m_nMask[2] = 0;
	m_nMask[3] = 0;
	Reset();	
	m_nMask[0] = 0; // undo the increment that Reset() does
	m_nStabs = 0;
}

/*virtual*/ GStabSearch::~GStabSearch()
{
	delete(m_pMins);
	delete(m_pRanges);
	delete(m_pVector);
}

void GStabSearch::Reset()
{
	m_nCurrentDim = 0;
	m_nMaskPos = 0;

	// Start at the global scope
	int i;
	for(i = 0; i < m_nDimensions; i++)
	{
		m_pMins[i] = m_dMin;
		m_pRanges[i] = m_dRange;
	}

	// Increment the mask
	i = 0;
	while(++(m_nMask[i]) == 0)
		i++;
	m_nStabs++;
}

/*virtual*/ void GStabSearch::Iterate()
{
	// Test the center of both halves
	int i;
	for(i = 0; i < m_nDimensions; i++)
		m_pVector[i] = m_pMins[i] + .5 * m_pRanges[i];
	m_pVector[m_nCurrentDim] = m_pMins[m_nCurrentDim] + .25 * m_pRanges[m_nCurrentDim];
	double dError1 = m_pCritic->Critique(m_pVector);
	m_pVector[m_nCurrentDim] = m_pMins[m_nCurrentDim] + .75 * m_pRanges[m_nCurrentDim];
	double dError2 = m_pCritic->Critique(m_pVector);

	// If the mask bit is zero, pick the better half, otherwise pick the worse half
	m_pRanges[m_nCurrentDim] *= .5;
	if(m_nMask[m_nMaskPos / 32] & (1 << (m_nMaskPos % 32)))
	{
		if(dError2 >= dError1)
			m_pMins[m_nCurrentDim] += m_pRanges[m_nCurrentDim];
	}
	else
	{
		if(dError2 < dError1)
			m_pMins[m_nCurrentDim] += m_pRanges[m_nCurrentDim];
	}

	// Advance
	if(++m_nCurrentDim >= m_nDimensions)
		m_nCurrentDim = 0;
	if(++m_nMaskPos >= 128)
		m_nMaskPos = 127;
	if(m_pRanges[m_nCurrentDim] < m_dTolerance)
		Reset();
}

#ifndef NO_TEST_CODE
#define TARGET_VALUE 3.14159
class GStabSearchTestCritic: public GRealVectorCritic
{
public:
	GStabSearchTestCritic() : GRealVectorCritic(1)
	{
	}

	virtual ~GStabSearchTestCritic()
	{
	}

	virtual double ComputeError(double* pVector)
	{
		double d = TARGET_VALUE - pVector[0];
		return d * d;
	}
};

// static
void GStabSearch::Test()
{
	GStabSearchTestCritic critic;
	GStabSearch search(&critic, 0, 4);
	int i;
	for(i = 0; i < 20; i++)
		search.Iterate();

	double dBestYet = critic.GetBestYet()[0];
	if(ABS(TARGET_VALUE - dBestYet) > .000001)
		throw "failed";
}
#endif // !NO_TEST_CODE