Abstract
An immutable multi-map is a many-to-many map data structure with expected fast insert and lookup operations. This data structure is used for applications processing graphs or many-to-many relations as applied in compilers, runtimes of programming languages, or in static analysis of object-oriented systems. Collection data structures are assumed to carefully balance execution time of operations with memory consumption characteristics and need to scale gracefully from a few elements to multiple gigabytes at least. When processing larger in-memory data sets the overhead of the data structure encoding itself becomes a memory usage bottleneck, dominating the overall performance. In this paper we propose AXIOM, a novel hash-trie data structure that allows for a highly efficient and type-safe multi-map encoding by distinguishing inlined values of singleton sets from nested sets of multi-mappings. AXIOM strictly generalizes over previous hash-trie data structures by supporting the processing of fine-grained type-heterogeneous content on the implementation level (while API and language support for type-heterogeneity are not scope of this paper). We detail the design and optimizations of AXIOM and further compare it against state-of-the-art immutable maps and multi-maps in Java, Scala and Clojure. We isolate key differences using microbenchmarks and validate the resulting conclusions on a case study in static analysis. AXIOM reduces the key-value storage overhead by 1.87 x; with specializing and inlining across collection boundaries it improves by 5.1 x.
Original language | English |
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Title of host publication | PLDI 2018 - Proceedings of the 39th ACM SIGPLAN Conference on Programming Language Design and Implementation |
Publisher | Association for Computing Machinery (ACM) |
Pages | 283-295 |
Number of pages | 13 |
ISBN (Electronic) | 9781450356985 |
DOIs | |
Publication status | Published - 11 Jun 2018 |
Event | 39th ACM SIGPLAN Conference on Programming Language Design and Implementation, PLDI 2018 - Philadelphia, United States Duration: 18 Jun 2018 → 22 Jun 2018 |
Conference
Conference | 39th ACM SIGPLAN Conference on Programming Language Design and Implementation, PLDI 2018 |
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Country/Territory | United States |
City | Philadelphia |
Period | 18/06/18 → 22/06/18 |
Keywords
- Data structures
- Functional programming
- Graph
- Hashtable
- JVM
- Many-to-many relation
- Multi-map
- Optimization
- Performance
- Persistent data structures