Lock free hash map. Mar 15, 2014 · There's also a lock free hashmap implementati...

Lock free hash map. Mar 15, 2014 · There's also a lock free hashmap implementation in java based on a state machine which should be possible to port to c++ with enough effort. Improved with bug fixes and a real build system. Implement Fixed-Size Memory Pool Allocator 2. Hash tries are a trie-based data structure with nearly ideal characteristics for the implementation of hash maps. May 14, 2019 · 文章浏览阅读1. at(5) which is indeed lock-free. Our design performs a factor of 7 or greater faster than a standard blocking approach. LockFreeHashMap This is an implementation of the lock-free hash map created by Dr. It is not a general-use HashMap and currently has slow write performance for write heavy uses. Map delivers exceptional speed, scalability Jun 10, 2025 · Lock-freedom offers significant advantages in terms of algorithm design, performance and scalability. Our experimental results show that our lock-free cuckoo hashing performs consistently better than two efficient lock-based hashing algorithms, the chained and the hopscotch hash-map, in different access pattern scenarios. A fundamental building block&#160;in software development is the usage of hash map data structures. A rust implementation of lock free cuckoo hashmap. - boundary/high-scale-lib I've run some benchmarks of evmap against a standard Rust HashMap protected by a reader-writer lock, as well as against chashmap — a crate which provides "concurrent hash maps, based on bucket-level multi-reader locks". Nov 24, 2017 · Lock-free algorithms tend to have more synchronization instructions in total, but all threads tend to be able to make progress at all times. I'm not sure it's lock-free, but hopefully you're interested in good multithreading performance, not particularly in lock-freeness. Proposal Checkpoint Poster Final Report Summary We implemented a concurrent extensible hash table library in C++ including three versions: a lock-free extensible hash table using CAS, which is based on a split-order list, a coarse-grained lock-based version, and a fine-grained lock-based version based on a two-level locking mechanism. This creates hotspots so that a map using read/write bin locks will show contention, while one supporting lock-free reads will show super-linear performance due to hardware cache effects. Jul 12, 2021 · README ¶ lockfree Golang lock-free concurrent Hashmap Table of Contents Overview Hashmap Queue Stack Benchmark Overview Golang's native data structures (such as map, List) are not designed to be thread-safe at first place. The total workload (10 threads) amounts to 100,000 keys, and 300,000 map operations. Getting Started This crate is available GitHub is where people build software. Oct 1, 2023 · I’ve stumbled across a fascinating article about arena memory management in C and how it’s used to write a concurrent lock free hashmap. However, if are using iterators you have to be careful to avoid deadlocks (i. Contribute to datenlord/lockfree-cuckoohash development by creating an account on GitHub. Map is a blazing-fast, memory-efficient HashMap library for . I’ve used lock-free tables similar to this one in real projects. However, to use it concurrently (and safely), one must put a lock on it. The hash table works on 32 bit keys and 32 bit values (although 0xffffffff is reserved for both keys and values). Aug 27, 2022 · Comprehensive C++ Hashmap Benchmarks 2022 Where I've spent way too much time creating benchmarks of C++ hashmaps Posted on August 27, 2022 High performance: our wait-free hash map design outperforms, by a factor of 15 or more, state of the art non-blocking designs. The source code can be seen on github The algorithm is not trivial at all with many interesting subtleties, like the key and the value being in adjacent entries in the array to reduce cache-misses, or the entry on the array for each key being "immutable" once assigned. Sep 17, 2025 · By leveraging lock-free data structures, the platform can process and analyze tweets simultaneously, providing insights in real-time. Contribute to NobodyXu/lock-free-hashmap development by creating an account on GitHub. After some bad experiences I'm skeptical about lock-free thread-safe structures, but having readable, clear code makes auditing the code for correctness much easier, and more, convinces me that the writer was able to understand their own code. Feb 1, 2016 · They come in three flavors: Junction’s Linear map is similar to the simple lock-free hash table I published a while ago, except that it also supports resizing, deleting entries, and templated key/value types. (By default 32 attempts to find a bucket are 接着，这个数据结构的实现需要是True Lock-free的。其实不存在什么True Lock-free，只是现在很多号称Lock free的实现其实压根不是Lock-free。并不是说没有用到mutex库就是Lock-free，这里wiki [1]有详细说明。但是通俗来说，你可以通过这种方法来分析自己的系统是不是Lock-free：假设程序运行的操作系统的任务 Aug 18, 2020 · A key role of a hash map is the ability to balance workloads by dynamically adjusting its internal data structures in order to provide the fastest possible access to the information. util. /// Note: This class currently assumes key and value are simple types that need no calls to the destructor. They are most useful for inter process communication, and often scale much better than lock-based structures with the number of operations and threads. This library is a Rust implementation, using epoch-based memory management to compensate for the lack of garbage collection. The code implements a lock free hash table using linear probing. Safety: our design goals help us achieve a high degree of safety; our design avoids the hazards of lock-based designs. Sep 3, 2022 · A Golang lock-free thread-safe HashMap optimized for fastest read access. Google Tech TalksMarch 28, 2007ABSTRACTI present a lock-free concurrent Hash Table implementation with better single-thread performance than most Hash Tables Lock free hashmap in Rust. Benchmark Hashmap Task set for each concurrent thread is to Set () 10,000 keys, Get () these 10,000 keys, and finally Del () all these keys. This is opposed to the traditional blocking - Attempt to fetch ``target_free`` free nodes from global lists - Attempt to pull any node from a global list and remove it from the hashmap - Attempt to pull any node from any CPU's list and remove it from the hashmap The number of nodes to borrow from the global list in a batch, ``target_free``, depends on the size of the map. May 30, 2013 · 无锁HashMap的难点与突破 HashMap主要有 插入 、 删除 、 查找 以及 ReHash 四种基本操作。 一个典型的HashMap实现，会用到一个数组，数组的每项元素为一个节点的链表。 Jun 16, 2025 · Stop Using RwLocks: How I Built a 30 Million ops/ sec Lock-Free HashMap in Pure Rust (and Why You Should Too) Your critical path is bottlenecked by an RwLock<HashMap<K, V>>. &#160;This work extends a previous lock-free hash map to support a Lock-free hash tables. It was inspired by Cliff Click’s non-blocking hash map in Java, but has a few differences. Aug 30, 2014 · Some years ago, Cliff Click came up with a resizable lock-free HashMap, which is a pretty cool feat. A node contains value, next ptr, and char array This is an atomic lock-free hash map implementation. Jun 5, 2013 · I’ve used lock-free tables similar to this one in real projects. . NET. GitHub Gist: instantly share code, notes, and snippets. Progress guarantees read operations are wait free population oblivious update operations are lock free Low memory footprint Very high lookup performance Reference implementation in Java Core hash table algorithm separate from Map / Set implementations Map implementation supports null keys and values (i. After migrating to a lock-free hash table, the worst-case framerate of the game improved from 4 FPS to 10 FPS when running in this mode. The structure itself requires no changes! Nov 28, 2023 · This is a write-oriented operation, and hence is NOT lock-free. The leapfrog crate contains two hash map implementations, HashMap, which is a single-threaded HashMap, and LeapMap, which is fast, concurrent version of the HashMap, where all operations can be performed concurrently from any number of threads. It’s built to outperform Dictionary<TKey,TValue> and ConcurrentDictionary<TKey,TValue> by providing SIMD acceleration, lock-free concurrency, and custom hashing algorithms. Around 150k messages/second are coming into the system via UDP. 10年前，cliff click博士就为关联 数据结构 ConcurrentHashMap 给出了一个采用open Address的无阻塞实现（NonBlockingHashMap）。其中为了减少线程之间执行顺序的依赖而采用的算法充满技巧性。这个算法宣称是无锁， 几乎可以保证任何时候停止某个特定线程都不会导致整体进程的停止 (极端情况下，这一点还是会 Jun 9, 2025 · I'm trying to implement a lock-free hashmap in C. Open addressing offers low memory overhead and improved cache locality when compared with node-based alternatives. L4 (Lock-Free on Read) Hashtable is a C++ library that provides a fixed-size hashtable, where keys and values are arbitrary bytes. Sep 28, 2015 · Shlomi Steinberg — Personal webpage This is prototype code to create a simple lock-free hash-map; the usage of this hash map has to be temporay cache-like, where you usualy write elements only once, you want to be fast, have virtually no memory fragmentation and know already approximately how many k/v pairs you will insert (or at least can tune through time). Contribute to bytbox/hashmap. The evmap benchmarks are unfortunately broken (1, 2), but since the author's aim is to be an influencer he refused to retract them. A collection of high-performance lock-free data structures for Rust. On the Latedays cluster consisting of two six-core Xeon E5-2620 processors, our 24-thread implementation achieved ~13x speedup over a C++11 std::unordered_map and is competitive with Intel’s concurrent_hash_map with little degradation in performance over various workloads. 接着，这个数据结构的实现需要是 True Lock-free 的。 其实不存在什么True Lock-free，只是现在很多号称Lock free的实现其实压根不是Lock-free。 并不是说没有用到mutex库就是Lock-free，这里wiki [1]有详细说明。 In this work, we designed a scalable, persistent hash map, PMap, optimized around large graph processing workloads. The table may also be concurrently resized to allow more elements to be inserted. Implemented using multi-level hash-tables (in a tree fashion) with ordered buckets. Contribute to Kanbenn/lockfree-map development by creating an account on GitHub. * Writers are sharded, but take a lock that only locks part of the map. Mar 7, 2026 · This page documents the internal cht (concurrent hash table) module that serves as moka's primary storage layer. In order to make something lock-free, at least one thread has to make progress after some time. A typical HashMap implementation uses an array where each element of the array is a linked list of nodes. A hash map size must be provided statically. Nice article! And particularly nice code. Performance We've run some benchmarks of concache against a standard Rust HashMap protected by a reader-writer lock, as well as against chashmap — a crate which provides "concurrent hash maps, based on bucket-level multi-reader locks". Two hash functions are assumed - one for hashing the key, and a second-order hash function for hashing hash values in case of hash collisions. For this list, we can use the operation method mentioned above to execute insert 、 delete as well as Find operating. To the best of our knowledge, our proposal is the first concurrent hash map design that puts together the following Jan 5, 2026 · Lock-Free Concurrent HashMap A high-performance, thread-safe hash map implementation in C++ using lock-free algorithms and atomic operations. Achieves up to 22. ConcurrentHashMap from the java SDK. You can check out his * Readers are always wait-free. The messages are updates against a set of 100k fixed keys. A fork of Cliff Click's High Scale Library. I think it’s generally understood that lock-free concurrency is usually considered as one of the harder problems in existence. A lock-free map. , a thread should not try to insert or erase a key while holding an iterator). 1). 0+ 87KB 1. Originally, this implementation here and recently here was created for Java, using garbage collection where necessary. Difficulties and breakthroughs in lock-free HashMap HashMap has four basic operations: insert, delete, find, and ReHash. L4 HashTable is optimized for lookup operations. Lock free hash maps I am working on a rule engine type of system. The foundation for most thread safe operations are atomic operations on std::shared_ptr. can be used as drop-in replacement for HashMap) Map / Set implementations support Apr 1, 2021 · An important contribution of the new hash map design is the ability to support the concurrent expansion of hash levels together with the removal of keys without violating the lock-free property and the consistency of the design. Design Thread-Safe Bounded Blocking Queue 3. The load factor of the table is set to 50% in the code, and the table size must be a power May 11, 2018 · 37 I don't see how your request is possible, at least not without some exceedingly clever lock-free data structures; what should happen if multiple threads need to insert new values that hash to the same location? In previous work, I've used a RwLock<HashMap<K, Mutex<V>>>. Cliff Click. Entries from the map CANNOT be deleted. Contribute to rolag/lockfreehashmap-rs development by creating an account on GitHub. OVERVIEW A hash table is a fundamental data structure which offers rapid storage and retrieval operations. This work extends a previous lock-free hash map design to also support lock-free compression. Contribute to dustinxie/lockfree development by creating an account on GitHub. Concurrent inserts, deletes, and lookups are supported by this hash table. It covers the SegmentedHashMap, BucketArray, pointer-tag semantics, linear probing, rehashing, and epoch-based memory reclamation. e. Nov 1, 2025 · This work redesigns a previous lock-free hash map to fully exploit the properties of the ERA theorem and to leverage the characteristics of multi-core cache-based architectures by minimizing the number of cache misses, which are a significant bottleneck in multi-core environments. Our multiprocessor data structure allows a large number of threads to concurrently insert, get, and remove information. - jfalkner/lockfree Thread-safe, lock-free hashmap in go. In one case, a game I worked on was bottlenecked by heavy contention on a shared lock whenever the memory tracker was enabled. Instead, it relies on the low-level Compare-And-Swap (CAS) operation to process concurrent A Golang lock-free thread-safe HashMap optimized for fastest read access. 84x speedup over mutex-based implementations on read-heavy workloads. Contribute to yang222-q/blaze_robot_system development by creating an account on GitHub. Faster. It's a great choice for a lot of use cases. Jun 9, 2025 · What you learned You navigated the trip-wires of atomic memory ordering, tamed epoch-based reclamation, and crafted a zero-lock hashmap that flies on modern hardware. Medical Care Robot Coordination System. Issuing this question verifies my thought. Each must still have its own arena, probably per-thread arenas, and so no implicit locking for allocation. Lock-free Cuckoo Hash Final Report Summary We implemented a fully-concurrent lock-free cuckoo hash table. This is an implementation of the lock-free hash map created by Dr. In this paper, we present a novel, simple and scalable hash trie map design that fully supports the concurrent search, insert and remove operations on hash maps. Lock-Free Stack Implementation and ABA Mitigation What you learned You navigated the trip-wires of atomic memory ordering, tamed epoch-based reclamation, and crafted a zero-lock hashmap that flies on modern hardware. Designed for real-time systems, game engines, caching layers, and data-intensive applications, Faster. moka-cht provides a lock-free hash table called HashMap that supports fully concurrent lookups, insertions, modifications, and deletions. This is a miniature implementation of a concurrent, lock-free (as in lock-less) hash map with weak keys where keys respect reference equality. This hash map is written in a way to make full use of the thread safety facilities offered by C++11. Contribute to boostbob/lockfree-hashmap-list development by creating an account on GitHub. A concurrent lock-free hash map for Rust. Lock free and alternate hash map implementation. However, it is completely lock free and does not use the latter to guarantee concurrent access. Achieves 6. It has its own interior locking, and uses a "generational" system (similar to Java's garbage collector) for memory management. (It doesn't actually free the elements when removing, I'm letting memory leak until it's destroyed). [src] Creates an empty LockFreeHashMap with the specified capacity, using hasher to hash the keys. An alternative would be to use map. May 22, 2018 · HashMap would suit? Have a look at Intel Threading Building Blocks, they have an interesting concurrent map. // We've acquired the resize lock, try to allocate a bigger hash table. Wait-freedom means that all threads make progress in a finite amount of time—an attribute that can be critical in real-time environments. If capacity is 0, the hash map will use the next power of 2 (i. Most (all?) const member functions of ConcurrentHashMap are lock-free Thanks your reply, I also read the code find the answer. would either of those suit your needs or is there a specific reason against them? Jan 29, 2020 · vyukov_hash_map - is a very fast hash map that uses fine grained locking for insert, erase and iteration; find operations are lock-free. Presentation LockFreeHashMap is a Java HashMap implementation based on the Java ConcurrentMap interface. Maybe give DashMap a try instead of tux_lockfree? Nov 23, 2019 · You can exploit this feature and make each bucket of the hashmap a (lock-free) (empty) linked-list, at construction, before the hashmap is used concurently. PMap is a lock-free non-volatile hash map with open addressing. 7k次。本文深入探讨了无锁HashMap的设计与实现，包括原子操作、无锁链表、无锁HashMap的难点与突破，以及具体的实现细节，如插入、查找、删除操作等。 Non-volatile memory (NVM) is an emerging memory technology that provides data persistence and higher densities than conventional DRAM. The hash map will be able to hold at least capacity elements without reallocating. A lock-free hash table that eanble multiple threads can concurrently read/write/delete up to 10M ops/s in mordern computer platform - divfor/atomic_hash DashMap and DashSet If you have data that fits well into a HashMap or HashSet, DashMap is a great choice. It's a lock-free hash map that can be shared between threads. No mutexes, no RWLocks, just pure atomic primitives. Additionally, "reference" Java code is available here and more recently here. Lock-free data structures are data structures that are thread and interrupt safe for concurrent use without having to use mutual exclusion mechanisms. The map provides the same features as the widely used java. In this work, we designed a scalable, persistent hash map, PMap Sep 30, 2023 · As a concurrent hash map For the finale, let’s convert upsert into a concurrent, lock-free hash map. Golang lock-free Hashmap and List. In general, lock-based structures and algorithms are better in low contention situations, and lock-free structures and algorithms are better in high contention situations. This crate provides thread-safe, lock-free implementations of common data structures that can be used in concurrent environments without the overhead of traditional locking mechanisms. The release of Intel Optane DC memory makes NVM a practical and testable technology. 5K SLoC LockFreeHashMap-rs A concurrent, lock-free hash map for Rust. // Note the acquire fence synchronizes with the release fence at the end of this block, and hence when 本人目前的工作因为涉及到一些内存中的高并发缓存实现，有用到 Cliff Click 大神早年的作品，即 Java 版的 NonblockingHashMap, 号称可以 scale 到 768 个 CPU。其思路主要是基于基础的 CAS(比较-交换)原语和精心… Here are the 14 titles, each 50 characters or fewer: 1. concurrent. The map and its elements will be destroyed/deallocated upon This hash map is written in a way to make full use of the thread safety facilities offered by C++11. The Rust standard library has an implementation of a HashMap. Mar 18, 2023 · How to insert into Hashmap from multiple threads at the same time? The other solution is to switch to a concurrency-aware hash map implementation like DashMap which handles the synchronisation in a much smarter way. go development by creating an account on GitHub. Also you can check CityHash lib EDIT: Actually TBB's hash map is not lock-free LockFreeHashMap This is an implementation of the lock-free hash map created by Dr. Contribute to anrikus/LockFreeHashMap development by creating an account on GitHub. If the key and value types support atomic operations then the map is lock-free, and when there is no atomic support for either the key or value, then 2 days ago · - * hashmap__for_each_key_entry - iterate over entries associated with given key + * perf_hashmap__for_each_key_entry - iterate over entries associated with given key Aug 20, 2021 · lock-free hashmap. Such a hash map removes entries containing collected keys by either: Inline removal (entries that contain to collected keys are removed as a result of interaction with the map). Mar 24, 2018 · Used in vampire_api LGPL-3. Thanks! A lock-free concurrent hash map, based on the 'folklore' implementation described in "Concurrent Hash Tables: Fast and General (?)!" by Maier et al. That is, multiple threads can call upsert concurrently on the same map. Mar 10, 2026 · LockMap LockMap is a high-performance, thread-safe HashMap implementation that provides fine-grained locking at the key level. Click released a talk about his hash map. Apr 10, 2014 · boost doesn't have hash maps because the STL does. More than 150 million people use GitHub to discover, fork, and contribute to over 420 million projects. When a valid bucket cannot be found get() will return a null pointer. /// Very simple lock free hash map that only allows insertion, retrieval and provides a fixed amount of buckets and fixed storage. As @EdChum stated, if you're using C++11 features, you could use the std::unordered_map, otherwise there's also just the std::map . For example, a lock-free queue can be used to buffer incoming tweets, while a lock-free hash map can be used to aggregate and analyze the data. This solves the first issue: accessing a bucket goes always through a lock-free linked-list. Usage Set a value for a key in the map: Concerning the lock-free hashmap of C, due to MSVC's lack of support for C11, it's written in C++11. Feb 6, 2021 · 文章浏览阅读475次。本文介绍了一个C++实现的True Lock-free HashMap，利用无锁链表处理哈希冲突，采用特殊的内存管理策略解决内存释放问题，以及如何避免ABA问题。通过反向位变换进行哈希桶的扩容，并实现延迟生成桶的机制，确保在高并发下依然保持高效和无锁特性。 Aug 19, 2015 · In this work we present the first design and implementation of a wait-free hash map. 16M ops/sec with balanced read/write performance Mar 16, 2015 · 无锁哈希表 (Lock-Free Hash Table) 是多线程编程中的理想数据结构，但是带有并发插入和删除的实现很少见于开源项目。博主对此做了一个巧妙的设计和实现，本文于此首次阐述设计思想。 通过考察各种基于CAS 原子操作的无锁数据结构实现，目前公认可实现无锁安全的数据结构是数组和单向队列。其他 Thread safe, lock-free data structures in C using GCC's built-in atomics. 🚀 A lock-free concurrent hashmap implementation in Go using atomic operations only. A common solution is to use mutex to synchronize access to data that are shared by multiple threads. This is very inefficient and can lead to deadlocks. hashmap Overview A Golang lock-free thread-safe HashMap optimized for fastest read access. Hash maps are fundamental data structures that associatively map keys to values, offering constant time lookup. 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