The document describes a MinMax normalization estimator and its model in a Spark environment, detailing the transformation process for data normalization. It includes class definitions, methods for fitting the model, and test specifications using JUnit for verifying the functionality of the estimator. Additionally, it references links to external resources for further information on Spark's capabilities and best practices.

8. class MinMaxNormEstimator(uid: String = UID[MinMaxNormEstimator])
extends UnaryEstimator[Real, Real](operationName = "minMaxNorm", uid = uid) {
def fitFn(dataset: Dataset[Real#Value]): UnaryModel[Real, Real] = {
val grouped = dataset.groupBy()
val max = grouped.max().first().getDouble(0)
val min = grouped.min().first().getDouble(0)
new MinMaxNormEstimatorModel(min = min, max = max, operationName = operationName, uid = uid)
}
}
class MinMaxNormEstimatorModel(val min: Double, val max: Double, operationName: String, uid: String)
extends UnaryModel[Real, Real](operationName = operationName, uid = uid) {
def transformFn: Real => Real = _.value.map(v => (v - min) / (max - min)).toReal
}

9. @RunWith(classOf[JUnitRunner])
class MinMaxNormEstimatorTest extends FlatSpec with Matchers {
val conf = new SparkConf().setMaster("local[*]")
implicit val spark = SparkSession.builder().config(conf).getOrCreate()
import spark.implicits._
"MinMaxNormEstimator" should ”fit a min/max model" in {
val data = spark.createDataset(Seq(-1.0, 0.0, 5.0, 1.0).map(Option(_)))
val model = new MinMaxNormEstimator().fitFn(data)
model match {
case m: MinMaxNormEstimatorModel =>
m.min shouldBe -1.0
m.max shouldBe 5.0
case m => fail(s"Unexpected model type: ${m.getClass}")
}
}
}

10. @RunWith(classOf[JUnitRunner])
class MinMaxNormEstimatorTest extends FlatSpec with Matchers with BeforeAndAfterAll {
val conf = new SparkConf().setMaster("local[*]")
implicit val spark = SparkSession.builder().config(conf).getOrCreate()
import spark.implicits._
override def afterAll(): Unit = {
super.afterAll()
spark.stop()
}
// …
}

11. trait TestSpark extends BeforeAndAfterAll { self: Suite =>
val kryoClasses: Array[Class[_]] = Array()
val conf: SparkConf = new SparkConf()
.setMaster("local[*]")
.registerKryoClasses(kryoClasses)
.set("spark.serializer", classOf[org.apache.spark.serializer.KryoSerializer].getName)
.set("spark.ui.enabled", false.toString) // disable Spark Application UI for faster tests
implicit lazy val spark = SparkSession.builder().config(conf).getOrCreate()
override def afterAll(): Unit = {
super.afterAll()
spark.stop()
}
}
abstract class SparkFlatSpec extends FlatSpec with Matchers with TestSpark

12. @RunWith(classOf[JUnitRunner])
class MinMaxNormEstimatorTest extends SparkFlatSpec {
import spark.implicits._
val data = spark.createDataset(Seq(-1.0, 0.0, 5.0, 1.0).map(Option(_)))
"MinMaxNormEstimator" should "fit a min/max model" in {
new MinMaxNormEstimator().fitFn(data) match {
case model: MinMaxNormEstimatorModel =>
model.min shouldBe -1.0
model.max shouldBe 5.0
case model =>
fail(s"Unexpected model type: ${model.getClass}")
}
}
}
More here:
https://github.com/apache/spark/blob/master/core/src/test/scala/org/apache/spark/SparkFunSuite.scala

13. https://jungiangenealogy.weebly.com/serpent.html

19. More here: https://github.com/saurfang/sbt-spark-submit
For Gradle: https://github.com/salesforce/TransmogrifAI/blob/master/gradle/spark.gradle

20. package org.apache.spark.ml
abstract class Transformer extends PipelineStage
{
def transform(dataset: Dataset[_]): DataFrame
}
type DataFrame = Dataset[Row]
trait Row extends Serializable {
def get(i: Int): Any
}

24. package org.apache.spark.util
case object ClosureUtils {
def checkSerializable(closure: AnyRef): Try[Unit] = scala.util.Try {
ClosureCleaner.clean(closure, checkSerializable = true, cleanTransitively = true)
}
}
package my.app
val x = new NonSerializable { def fun() = ??? }
ClosureUtils.checkSerializable(x.fun _) // make the check early at application start
udf { d: Double => x.fun(d) } // if we are here – it’s safe to use x

25. Read more:
https://docs.transmogrif.ai/en/stable/developer-guide/index.html#wrapping-a-non-serializable-external-
library
udf { d: Double => new NonSerializable().fun(d) }
object NonSerializable {
val instance = new NonSerializable
}
udf { d: Double => NonSerializable.instance.fun(d) }

26. val ds: Dataset[_] = ???
println("Dataset schema & plans:")
ds.printSchema()
ds.explain(extended = true)
https://databricks.com/blog/2015/04/13/deep-dive-into-spark-sqls-catalyst-optimizer.html
https://databricks.com/blog/2016/05/23/apache-spark-as-a-compiler-joining-a-billion-rows-per-second-on-a-laptop.html

27. https://github.com/apache/spark/blob/master/sql/catalyst/src/main/scala/org/apache/spark/sql/inter
nal/SQLConf.scala#L780

28. // Apply all the transformers one by one as org.apache.spark.ml.Pipeline does
transformers.zipWithIndex.foldLeft(data) { case (df, (transformer, i)) =>
val persist = i > 0 && i % persistEveryKStages == 0
val newDF = transformer.transform(df)
if (!persist) newDF
else {
// Converting to RDD and back here to break up Catalyst [SPARK-13346]
val persisted = newDF.rdd.persist()
lastPersisted.foreach(_.unpersist())
lastPersisted = Some(persisted)
spark.createDataFrame(persisted, newDF.schema)
}
}
https://github.com/salesforce/TransmogrifAI/blob/master/core/src/main/scala/com/salesforce/op/uti
ls/stages/FitStagesUtil.scala#L150

30. More here: https://spark.apache.org/docs/latest/tuning.html

34. https://github.com/salesforce/TransmogrifAI/blob/master/utils/src/main/scala/com/salesforce/op
/utils/spark/OpSparkListener.scala
https://github.com/LucaCanali/sparkMeasure
val myListener = new MySparkListener(
appName = spark.sparkContext.appName,
appId = spark.sparkContext.applicationId
) {
override def onApplicationEnd(applicationEnd: SparkListenerApplicationEnd): Unit = {
super.onApplicationEnd(applicationEnd)
val m = super.metrics
log.info("Total run time: {}", m.appDurationPretty)
MyApp.onApplicationEnd(m)
}
}
spark.sparkContext.addSparkListener(myListener) // add the listener
def onApplicationEnd(metrics: AppMetrics): Unit = { /* consume metrics */ }

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