ItemCF(基于物品的协同过滤推荐算法).zip

package com.lt.hadoop.step2; import org.apache.hadoop.io.LongWritable; import org.apache.hadoop.io.Text; import org.apache.hadoop.mapreduce.Mapper; import java.io.BufferedReader; import java.io.FileReader; import java.io.IOException; import java.text.DecimalFormat; import java.util.ArrayList; import java.util.List; /** * Created by taoshiliu on 2017/10/8. */ public class Mapper2 extends Mapper<LongWritable,Text,Text,Text> { private Text outKey = new Text(); private Text outvalue = new Text(); private List<String> cacheList = new ArrayList<String>(); private DecimalFormat df = new DecimalFormat("0.00"); protected void setup(Context context) throws IOException,InterruptedException { super.setup(context); //通过输入流将全局缓存中的matrix2读入List<String>中 FileReader fr = new FileReader("itemUserScore"); BufferedReader br = new BufferedReader(fr); String line = null; while ((line = br.readLine()) != null) { cacheList.add(line); } fr.close(); br.close(); } protected void map(LongWritable key,Text value,Context context) throws IOException,InterruptedException { String row_matrix1 = value.toString().split("\t")[0]; String[] column_value_array_matrix1 = value.toString().split("\t")[1].split(","); double denominator1 = 0; //计算左矩阵行的空间距离 for(String column_value : column_value_array_matrix1) { String score = column_value.split("_")[1]; denominator1 += Double.valueOf(score) * Double.valueOf(score); } denominator1 = Math.sqrt(denominator1); for(String line : cacheList) { String row_matrix2 = line.toString().split("\t")[0]; String[] column_value_array_matrix2 = line.toString().split("\t")[1].split(","); double denominator2 = 0; //计算右矩阵行的空间距离 for(String column_value : column_value_array_matrix2) { String score = column_value.split("_")[1]; denominator2 += Double.valueOf(score) * Double.valueOf(score); } denominator2 = Math.sqrt(denominator2); int numerator = 0; for(String column_value_matrix1 : column_value_array_matrix1) { String column_matrix1 = column_value_matrix1.split("_")[0]; String value_matrix1 = column_value_matrix1.split("_")[1]; for(String column_value_matrix2:column_value_array_matrix2) { if(column_value_matrix2.startsWith(column_matrix1 + "_")) { String value_matrix2 = column_value_matrix2.split("_")[1]; numerator += Integer.valueOf(value_matrix1) * Integer.valueOf(value_matrix2); } } } //余弦相似度 double cos = numerator / (denominator1 * denominator2); if(cos == 0) { continue; } outKey.set(row_matrix1); outvalue.set(row_matrix2 + "_" + df.format(cos)); context.write(outKey,outvalue); } } }