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In this micro talk, I'll review the basic theory behind hash functions and hash tables, show you the new internal data structures that Ruby 2.0 uses to save keys and values, and present some performance data that proves this optimization exists and how much time it will actually save you.
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In the micro talk titled "Why Hashes Will Be Faster in Ruby 2.0," Pat Shaughnessy delves into the internal mechanics of hash functions and hash tables in Ruby, particularly focusing on the enhancements introduced in Ruby 2.0 that improve hash performance. This presentation highlights the evolution of hash implementation from previous versions to Ruby 2.0. Key points discussed include: - **Understanding Hashes**: Shaughnessy begins with a brief overview, reminding the audience that as Ruby developers, they are already familiar with hashes and their basic operations. He emphasizes the internal implementation of hash objects rather than basic usage. - **Hash Tables Explained**: The talk explains that Ruby utilizes hash tables, which consist of bins or buckets to store key-value pairs. Each bin is determined by a hash function that transforms a value into a hash value, which is then mapped to a specific bin using modulus operations. - **Collision Handling**: The speaker describes how collisions are managed in hash tables, with multiple entries allowed in the same bin through linked lists, illustrating the design's efficiency. - **Improvements in Ruby 2.0**: The core team in Ruby 2.0 made significant changes to enhance performance. The malloc function, which allocates memory, was eliminated during the insertion process, and keys and values are now stored directly in an array at the top level of the hash. This makes the hash structure more compact and eliminates overhead associated with pointers. - **Performance Evaluation**: Shaughnessy presents performance data comparing various hash sizes, illustrating faster insertions in Ruby 2.0 compared to earlier versions, especially when dealing with up to six entries. - **Real-world Testing**: To corroborate the improvements in speed, Shaughnessy tested a Rails application, finding a performance enhancement of over 2.5% under typical use cases. He highlights that while hashes may appear minimal, they are integral to numerous underlying operations in Ruby and Rails applications. - **Conclusion and Further Interest**: Shaughnessy concludes by expressing excitement about Ruby's internal workings and encourages those interested to explore his upcoming book, "Ruby Under a Microscope." Ultimately, the talk underscores Ruby 2.0's enhancements in how hashes function efficiently, significantly reducing performance bottlenecks while ensuring backwards compatibility.
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