zhengruifeng commented on PR #38203:
URL: https://github.com/apache/spark/pull/38203#issuecomment-1274301748

   take 
[`RankingMetricsExample`](https://github.com/apache/spark/blob/e3058ba17cb4512537953eb4ded884e24ee93ba2/examples/src/main/scala/org/apache/spark/examples/mllib/RankingMetricsExample.scala)
 for example:
   
   ```
   import org.apache.spark.mllib.evaluation.{RankingMetrics, RegressionMetrics}
   import org.apache.spark.mllib.recommendation.{ALS, Rating}
   
   
   val ratings = 
spark.read.textFile("data/mllib/sample_movielens_data.txt").rdd.map { line =>
       val fields = line.split("::")
       Rating(fields(0).toInt, fields(1).toInt, fields(2).toDouble - 2.5)
   }.cache()
   
   // Map ratings to 1 or 0, 1 indicating a movie that should be recommended
   val binarizedRatings = ratings.map(r => Rating(r.user, r.product, if 
(r.rating > 0) 1.0 else 0.0)).cache()
   
   
   val numIterations = 1
   val rank = 10
   val lambda = 0.01
   val model = ALS.train(ratings, rank, numIterations, lambda)
   
   val userRecommended = model.recommendProductsForUsers(10)
   
   userRecommended.count()
   ```
   
   before:
   
![image](https://user-images.githubusercontent.com/7322292/195038806-acad9193-838e-4a32-9ec4-5e390d143e61.png)
   
   
   after:
   
![image](https://user-images.githubusercontent.com/7322292/195038629-9b249726-05a2-4b90-a804-7aef089f505f.png)
   
   the shuffle size was reduced from `310.1 KiB` to `110.9 KiB`


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