实习日记：图像检索算法 LSH 的总结与分析

#include <string>
inline int getPosition(int V[], std::string s, int N)
{
	int position = 0;
	for(int col = 0; col < k; ++col)
	{
		position += V[col] * (s[col] - ‘0‘);
		position %= M;
	}
	return position;
}

inline int distance(bool v1[], bool v2[], int N)
{
	int d = 0;
	for(int i = 0; i < N; ++i)
		d += v1[i] ^ v2[i];

	return d;

}

#include "Head.h"
#include "D:\\LiYangGuang\\VSPRO\\MYLSH\\computeDistance.h"
using namespace std;
// length of sub hashtable, as well the number of elements.
const int MAX_Q = 1000; 

HT HTSet[l];

bool data[n][128];
bool extDat[l][n][k];

bool query[MAX_Q][128]; // set the query item to 1000.

int main(int argc, char *argv)
{
	/************************************************************************/
	/*             Firstly, create the HashTables                           */
	/************************************************************************/
	char *filename = "D:\\LiYangGuang\\VSPRO\\MYLSH\\data.txt";
	loadData(data, n, filename);
	createTable(HTSet, data, extDat);
	insert(HTSet,extDat);
	standHash(HTSet);

	/************************************************************************/
	/*              Secondly, start the LSH search                          */
	/************************************************************************/

	char *queryFile = "D:\\LiYangGuang\\VSPRO\\MYLSH\\query.txt";
	loadData(query, MAX_Q, queryFile);
	clock_t time0 = clock();
	for(int qId = 0; qId < MAX_Q; ++qId)
	{
		vector<int> record;
		clock_t timeA = clock();
		search(record, query[qId], HTSet);
		set<int> Dis;
		for(size_t i = 0; i < record.size(); ++i)
			Dis.insert(distance(data[record[i]], query[qId]));
		clock_t timeB = clock();
		cout << "第 " << qId + 1 << " 次查询时间：" << timeB - timeA << endl;
	}
	clock_t time1 = clock();
	cout << "总查询时间：" << time1 - time0 << endl;


    return 0;

}

#include <string>
#include <fstream>

void loadData(bool (*data)[128], int n, char* filename)
{
	std::ifstream ifs;
	ifs.open(filename, std::ios::in);
	for(int row = 0; row < n; ++row)
	{
		std::string line;
		getline(ifs, line);
		for(int col = 0; col < 128; ++col)
			data[row][col] = (line[col] - ‘0‘) & 1;
	/*	std::cout << row << std::endl;*/

	}
	ifs.close();
}

#include "HashTable.h"
#include <ctime>

void createTable(HT HTSet[], bool data[][128], bool extDat[][n][k] )
{
	srand((unsigned)time(NULL));
	for(int tableNum = 0; tableNum < l; ++tableNum)  
	{      /*	creat the ith Table;*/

		for(int randNum = 0; randNum < k; ++randNum)
		{
			HTSet[tableNum].R[randNum] = rand() % 128;
			HTSet[tableNum].RNum[randNum] = rand() % M;

			for(int item = 0; item < n; ++item)
			{
				extDat[tableNum][item][randNum] = 
					data[item][HTSet[tableNum].R[randNum]];
			}
		}
	}
}

#include "HashTable.h"
#include <iostream>
#include <map>
using namespace std;

map<string, int> deRepeat;
bool equal(bool V[], bool V2[], int n)
{
	int i = 0;
	while(i < n)
	{
		if(V[i] != V2[i])
			return false;
	}
	return true;
}

string itoa(bool *v, int n, string s)
{
	for(int i = 0; i < n; ++i)
		s.push_back(v[i]+‘0‘);
	return s;
}

void insert(HT HTSet[], bool (*extDat)[n][k])
{
	for(int t = 0; t < l; ++ t) /* t: table */
	{
		int bktNum = 0;
		bucket bkt;
		bkt.key = string(itoa(extDat[t][0], k, string("")));
		bkt.elem.push_back(0);
		HTSet[t].BukSet.push_back(bkt);
		deRepeat.insert(make_pair(bkt.key, bktNum++)); // 0 为 bucket 的位置
		for(int item = 1; item < n; ++item)
		{
			cout << item << endl;
			string key = itoa(extDat[t][item], k, string(""));
			//map<string, int>::iterator it = deRepeat.find(key);
			if(deRepeat.find(key) != deRepeat.end())
			{
				HTSet[t].BukSet[deRepeat.find(key)->second].elem.push_back(item);
				cout << "exist" << endl;
			}
			else{
				bucket bkt2;
				bkt2.key = key;
				bkt2.elem.push_back(item);
				HTSet[t].BukSet.push_back(bkt2);
				deRepeat.insert(make_pair(bkt2.key, bktNum++));
				cout << "creat" << endl;
			}
		}
		deRepeat.clear();
	}
}

#include "HashTable.h"
#include <iostream>
#include "getPosition.h"

void standHash(HT HTSet[])
{
	for(int t = 0; t < l; ++t)
	{
		int BktLen = HTSet[t].BukSet.size();
		for(int b = 0; b < BktLen; ++b)
		{
			int position = getPosition(HTSet[t].RNum, HTSet[t].BukSet[b].key, k);
			INT *pIn = &HTSet[t].Hash2[position];
			while(pIn->used && pIn->next != NULL)
				pIn = pIn->next;
			if(pIn->used){
				pIn->next = new INT;
				pIn->next->val = b;
				pIn->next->used = true;
			}else{
				pIn->val = b;
				pIn->used = true;
			}
		}
		std::cout << "the " << t << "th HashTable has been finished." << std::endl;
	}
}

#include "HashTable.h"
#include "getPosition.h"
#include <vector>
using namespace std;

void search(vector<int>& record, bool query[128], HT HTSet[])
{
	for(int t = 0; t < l; ++t)
	{
		string temKey;
		int temPos = 0;
		for(int c = 0; c < k; ++c)
			temKey.push_back(query[HTSet[t].R[c]] + ‘0‘);
		temPos = getPosition(HTSet[t].RNum, temKey, k);
		vector<int> bktId;
		INT *p = &HTSet[t].Hash2[temPos];
		while(p != NULL && p->used)
		{
			bktId.push_back(p->val);
			p = p->next;
		}
		for(size_t i = 0; i < bktId.size(); ++i)
		{
			bucket temB = HTSet[t].BukSet[bktId[i]];
			if(temKey == temB.key)
			{
				for(size_t j = 0; j < temB.elem.size(); ++j)
					record.push_back(temB.elem[j]);
			}
		}
	}
}