数据算法 Hadoop/Spark大数据处理---第十章

2023年10月1日 245次阅读 来源: 林子康better

本章为推荐引擎

本章为基于电影内容的推荐，假设输入为<用户，电影，评分>，输入为<电影1，电影2><三种算法的相似度>。

本章实现方式

  1. 基于传统spark来实现
  2. 基于传统Scala来实现

本章实现方式的思路

– spark：
  • 1.先创建JavaSparkContext，textFile读入文件。
  • 2.对String进行切分，转换成key = Movie3 value=(User1,3)。
  • 3.之后对key进行分组，得到key=Movie2 value=[(User1,4),(User2,5),(User3,3),(User4,3)]
  • 4.对Uset进行groupByKey，得到key = user value = Tuple3[Movie2,4,4],Tuple3[Movie1,2,4]之类的。
  • 5.对value进行操作，转换成<Movie1,Movie2><1 10 2 20 2 1 4> <Movie1,Movie3><1 10 3 30 3 1 9>
  • 6.对<Movie1,Movie2>进行分组，转换成：<Movie1,Movie2> [<1 10 2 20 2 1 4> <2 10 3 20 6 4 9>]
  • 7.之后可以通过pearsonCorrelation，cosineCorrelation，jaccardCorrelation公式来求得两个movie之间的相似值

++基于传统spark来实现++

//对String进行切分
 JavaPairRDD<String, Tuple2<String, Integer>> moviesRDD = usersRatings.mapToPair(new PairFunction<String, String, Tuple2<String, Integer>>() {
            @Override
            public Tuple2<String, Tuple2<String, Integer>> call(String s) throws Exception {
                String[] record = s.split("\t");
                String user = record[0];
                String movie = record[1];
                Integer rating = new Integer(record[2]);
                Tuple2<String, Integer> userAndRating = new Tuple2<>(user, rating);
                return new Tuple2<>(movie, userAndRating);
            }
        });
 //生成key=User1 value=Tuple3[Movie2,4,4]  key=User2 value=Tuple3[Movie2,5,4]
JavaPairRDD<String, Tuple3<String, Integer, Integer>> usersRDD = moviesGrouped.flatMapToPair(new PairFlatMapFunction<Tuple2<String, Iterable<Tuple2<String, Integer>>>, String, Tuple3<String, Integer, Integer>>() {
            @Override
            public Iterator<Tuple2<String, Tuple3<String, Integer, Integer>>> call(Tuple2<String, Iterable<Tuple2<String, Integer>>> s) throws Exception {
                ArrayList<Tuple2<String, Integer>> listOfUsersAndRating = new ArrayList<>();
                //保存movie
                String movie = s._1;
                Iterable<Tuple2<String, Integer>> pairsOfUserAndRating = s._2;
                //numberOfRates用于数一个movie有几个
                int numberOfRates = 0;
                for (Tuple2<String, Integer> t2 : pairsOfUserAndRating) {
                    numberOfRates++;
                    listOfUsersAndRating.add(t2);
                }
                ArrayList<Tuple2<String, Tuple3<String, Integer, Integer>>> results = new ArrayList<>();
                for (Tuple2<String, Integer> t2 : listOfUsersAndRating) {
                    String user = t2._1;
                    Integer rating = t2._2;
                    Tuple3<String, Integer, Integer> t3 = new Tuple3<>(movie, rating, numberOfRates);
                    results.add(new Tuple2<>(user, t3));
                }
                return results.iterator();
            }
        });
//<Movie1,Movie2><1 10 2 20 2 1 4> <Movie1,Movie3><1 10 3 30 3 1 9>的格式，之后就可以给其它的公式去求相似度了
 JavaPairRDD<Tuple2<String, String>, Tuple7<Integer, Integer, Integer, Integer, Integer, Integer, Integer>> moviePairs = groupedbyUser.flatMapToPair(new PairFlatMapFunction<Tuple2<String, Iterable<Tuple3<String, Integer, Integer>>>, Tuple2<String, String>,
                Tuple7<Integer, Integer, Integer, Integer, Integer, Integer, Integer>>() {
            @Override
            public Iterator<Tuple2<Tuple2<String, String>, Tuple7<Integer, Integer, Integer, Integer, Integer, Integer, Integer>>>
            call(Tuple2<String, Iterable<Tuple3<String, Integer, Integer>>> s) throws Exception {
                String user = s._1;
                Iterable<Tuple3<String, Integer, Integer>> movies = s._2;
                //把第二部分Iterable的Tuple3[Movie2,4,4]变成{movie2,4,4}的形式
                List<Tuple3<String, Integer, Integer>> listOfMovies = toList(movies);
                //返回的大概是以某个字母为开始，然后两两的组合Tuple3[Movie2,4,4]，一个大的List包含着包含各个小字母的小的List的三元数组
                List<List<Tuple3<String, Integer, Integer>>> comb2 = Combination.findSortedCombinations(listOfMovies, 2);
                ArrayList<Tuple2<Tuple2<String, String>, Tuple7<Integer, Integer, Integer, Integer, Integer, Integer, Integer>>> result = new ArrayList<>();
                for (List<Tuple3<String, Integer, Integer>> twoMovies : comb2) {
                    //从组合的 movie对中获取
                    Tuple3<String, Integer, Integer> movie1 = twoMovies.get(0);
                    Tuple3<String, Integer, Integer> movie2 = twoMovies.get(1);
                    //生成两个Movies列表
                    Tuple2<String, String> k3 = new Tuple2<String, String>(movie1._1, movie2._1);
                    Tuple7<Integer, Integer, Integer, Integer, Integer, Integer, Integer> v3 = getTuple7(movie1, movie2);
                    //这一步生成大概像：<Movie1,Movie2><1 10 2 20 2 1 4> <Movie1,Movie3><1 10 3 30 3 1 9>
                    Tuple2<Tuple2<String, String>, Tuple7<Integer, Integer, Integer, Integer, Integer, Integer, Integer>> k3v3 = new Tuple2<>(k3, v3);
                    result.add(k3v3);
                }
                return result.iterator();
            }
        });

++基于传统Scala来实现++

//对String进行切分
val userMovieRating = userRatings.map(line =>{
      val tokens = line.split("\\s+")
      // user      movie      rate
      (tokens(0),tokens(1),tokens(2).toInt)
    })
    
//获得每部电影看的人数,对movie进行排序
    val numberOfRatePerMovie = userMovieRating.map(umr => (umr._2,1)).reduceByKey(_+_)
    
 //先从（umr._2, （(umr._1, umr._3)，numberOfRatersPerMovie）） =（movie, （(user, rate)，count）)
    //再到(user,movie,rate,count)
    val userMovieRatingNumberOfRater = userMovieRating.map(umr =>(umr._2,(umr._1,umr._3))).join(numberOfRatePerMovie)
      .map(tuple =>(tuple._2._1._1,tuple._1,tuple._2._1._2,tuple._2._2))

//对user进行排序得到User1 [<Movie1,1,10>,<Movie2,2,20>,<Movie3,3,30>],后面是一个Iterable
    val groupByUser = userMovieRatingNumberOfRater.map(f =>(f._1,(f._2,f._3,f._4))).groupByKey()
    
//生成<Movie2><1 10 2 20 2 1 4>
val moviePairs = groupByUser.flatMap(tuple=>{
      //对movie进行排序，防止重复
      val sorted = tuple._2.toList.sortBy(f => f._1)
      val tuple7 = for{
        movie1 <- sorted
        movie2 <- sorted
        if(movie1._1 < movie2._1)
        ratingProduct = movie1._2 * movie2._2
        rating1Squared = movie1._2 * movie1._2
        rating2Squared = movie2._2 * movie2._2
      }yield {
        ((movie1._1, movie2._1), (movie1._2, movie1._3, movie2._2, movie2._3, ratingProduct, rating1Squared, rating2Squared))
      }
      tuple7
    })
//<Movie1,Movie2> [<1 10 2 20 2 1 4> <2 10 3 20 6 4 9>]
 val moviePairsGrouped = moviePairs.groupByKey()
 
//最后先用foldRight向右折叠求出各类总分，然后再用三个公式求
val result = moviePairsGrouped.mapValues(itr =>{
      val groupSize = itr.size
      //foldRight为向右折叠，把所有的值相加起来
      val (rating1, numOfRaters1, rating2, numOfRaters2, ratingProduct, rating1Squared, rating2Squared) =
        itr.foldRight((List[Int](), List[Int](), List[Int](), List[Int](), List[Int](), List[Int](), List[Int]()))((a, b) =>
          (
            a._1 :: b._1,
            a._2 :: b._2,
            a._3 :: b._3,
            a._4 :: b._4,
            a._5 :: b._5,
            a._6 :: b._6,
            a._7 :: b._7))
      val dotProduct = ratingProduct.sum // sum of ratingProd
      val rating1Sum = rating1.sum // sum of rating1
      val rating2Sum = rating2.sum // sum of rating2
      val rating1NormSq = rating1Squared.sum // sum of rating1Squared
      val rating2NormSq = rating2Squared.sum // sum of rating2Squared
      val maxNumOfumRaters1 = numOfRaters1.max // max of numOfRaters1
      val maxNumOfumRaters2 = numOfRaters2.max // max of numOfRaters2

      val numerator = groupSize * dotProduct - rating1Sum * rating2Sum
      val denominator = math.sqrt(groupSize * rating1NormSq - rating1Sum * rating1Sum) *
        math.sqrt(groupSize * rating2NormSq - rating2Sum * rating2Sum)
      //正则关联度
      val pearsonCorrelation = numerator / denominator
      //欧氏距离
      val cosineCorrelation = dotProduct / (math.sqrt(rating1NormSq) * math.sqrt(rating2NormSq))
      //曼哈顿距离
      val jaccardCorrelation = groupSize.toDouble / (maxNumOfumRaters1 + maxNumOfumRaters2 - groupSize)

      (pearsonCorrelation, cosineCorrelation, jaccardCorrelation)
    })
    原文作者：林子康better
    原文地址: https://www.jianshu.com/p/1f08f3ca4e97
    本文转自网络文章，转载此文章仅为分享知识，如有侵权，请联系博主进行删除。
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