Book Image

Mastering Apache Spark 2.x - Second Edition

Book Image

Mastering Apache Spark 2.x - Second Edition

Overview of this book

Apache Spark is an in-memory, cluster-based Big Data processing system that provides a wide range of functionalities such as graph processing, machine learning, stream processing, and more. This book will take your knowledge of Apache Spark to the next level by teaching you how to expand Spark’s functionality and build your data flows and machine/deep learning programs on top of the platform. The book starts with a quick overview of the Apache Spark ecosystem, and introduces you to the new features and capabilities in Apache Spark 2.x. You will then work with the different modules in Apache Spark such as interactive querying with Spark SQL, using DataFrames and DataSets effectively, streaming analytics with Spark Streaming, and performing machine learning and deep learning on Spark using MLlib and external tools such as H20 and Deeplearning4j. The book also contains chapters on efficient graph processing, memory management and using Apache Spark on the cloud. By the end of this book, you will have all the necessary information to master Apache Spark, and use it efficiently for Big Data processing and analytics.
Table of Contents (21 chapters)
Title Page
Credits
About the Author
About the Reviewer
www.PacktPub.com
Customer Feedback
Preface
10
Deep Learning on Apache Spark with DeepLearning4j and H2O

Memory management beyond the Java Virtual Machine Garbage Collector


Note

The JVM Garbage Collector is in support of the whole object's life cycle management the JVM provides. Whenever you see the word new in Java code, memory is allocated in a JVM memory segment called heap.

Java completely takes care of memory management and it is impossible to overwrite memory segments that do not belong to you (or your object). So if you write something to an object's memory segment on the heap (for example by updating a class property value of type Integer, you are changing 32 bit on the heap) you don't use the actual heap memory address for doing so but you use the reference to the object and either access the object's property or use a setter method.

So we've learned about new allocated memory on the heap, but how does it ever get freed? This is where the Java Garbage collector kicks in. It continuously monitors how many active references to a certain object on the heap exist and once no more references...