Train AutoML Model in Sparkling Water

Sparkling Water provides API in Scala and Python for H2O AutoML. The following sections describe how to train an AutoML model in Sparkling Water in both languages.

Scala

First, let’s start Sparkling Shell as

./bin/sparkling-shell

Start H2O cluster inside the Spark environment

import org.apache.spark.h2o._
import java.net.URI
val hc = H2OContext.getOrCreate(spark)

Parse the data using H2O and convert them to Spark Frame

val frame = new H2OFrame(new URI("https://raw.githubusercontent.com/h2oai/sparkling-water/master/examples/smalldata/prostate/prostate.csv"))
val sparkDF = hc.asDataFrame(frame).withColumn("CAPSULE", $"CAPSULE" cast "string")
val Array(trainingDF, testingDF) = sparkDF.randomSplit(Array(0.8, 0.2))

Create a H2OAutoML instance and configure it according your use case via provided setters. If feature columns are not specified explicitly, all columns excluding label, fold, weight and ignored columns are considered as features.

import ai.h2o.sparkling.ml.algos.H2OAutoML
val automl = new H2OAutoML()
automl.setLabelCol("CAPSULE")
automl.setIgnoredCols(Array("ID"))

By default, AutoML goes through a huge space of H2O algorithms and their hyper-parameters which requires some time. If you wish to speed up the training phase, you can exclude some H2O algorithms and limit the number of trained models.

automl.setExcludeAlgos(Array(ai.h2o.automl.Algo.GLM))
automl.setMaxModels(10)

Train the AutoML model. The training phase returns the best model according to the sortMetric. If it’s not specified, the sortMetric is chosen automatically.

automl.setSortMetric("AUC")
val model = automl.fit(trainingDF)

You can also get raw model details by calling the getModelDetails() method available on the model as:

model.getModelDetails()

Run Predictions

model.transform(testingDF).show(false)

Python

First, let’s start PySparkling Shell as

./bin/pysparkling

Start H2O cluster inside the Spark environment

from pysparkling import *
hc = H2OContext.getOrCreate(spark)

Parse the data using H2O and convert them to Spark Frame

import h2o
frame = h2o.import_file("https://raw.githubusercontent.com/h2oai/sparkling-water/master/examples/smalldata/prostate/prostate.csv")
sparkDF = hc.asSparkFrame(frame)
sparkDF = sparkDF.withColumn("CAPSULE", sparkDF.CAPSULE.cast("string"))
[trainingDF, testingDF] = sparkDF.randomSplit([0.8, 0.2])

Create a H2OAutoML instance and configure it according your use case via provided setters or named constructor parameters. If feature columns are not specified explicitly, all columns excluding label, fold, weight and ignored columns are considered as features.

from pysparkling.ml import H2OAutoML
automl = H2OAutoML(labelCol="CAPSULE", ignoredCols=["ID"])

By default, AutoML goes through a huge space of H2O algorithms and their hyper-parameters which requires some time. If you wish to speed up the training phase, you can exclude some H2O algorithms and limit the number of trained models.

automl.setExcludeAlgos(["GLM"])
automl.setMaxModels(10)

Train the AutoML model. The training phase returns the best model according to the sortMetric. If it’s not specified, the sortMetric is chosen automatically.

automl.setSortMetric("AUC")
model = automl.fit(trainingDF)

You can also get raw model details by calling the getModelDetails() method available on the model as:

model.getModelDetails()

Run Predictions

model.transform(testingDF).show(truncate = False)

Enabling XGBoost Models when Running Sparkling Water in a Distributed Environment (YARN)

The multi-node XGBoost algorithm is considered as an experimental feature of AutoML. Thus the XGBoost algorithm is disabled for AutoML by default when running Sparkling Water in a distributed environment (e.g. on YARN). When Sparkling Water is run in the local mode, XGBoost is enabled.

Scala

To enable the algorithm on YARN, sparkling-shell has to be executed with the extra driver option as:

./bin/sparkling-shell --conf spark.driver.extraJavaOptions=-Dsys.ai.h2o.automl.xgboost.multinode.enabled=true

Python

To enable the algorithm on YARN, pysparkling has to be executed with the extra driver option as:

./bin/pysparkling --conf spark.driver.extraJavaOptions=-Dsys.ai.h2o.automl.xgboost.multinode.enabled=true

The statement above also holds for executing Sparkling Water with the external backend and connecting Sparkling Water to an existing H2O cluster. Other configuration steps are not necessary for enabling XGBoost in AutoML.