scala bitset performance

December 12th, 2020

Learn more. scala> s res1: scala.collection.immutable.BitSet = BitSet(1, 64, 128) I suppose it makes sense to keep this implementation around for performance reasons but I'd prefer to hide it better. Bitsets are sets of non-negative integers and are represented as variable-size arrays of bits packed into 64-bit words. Since the compiler performs type checking at compile time instead of runtime, it lets the developer notice and resolve errors at the compile time itself. Performance characteristics of sequence types: Performance characteristics of set and map types: Footnote: 1 Assuming bits are densely packed. books i’ve written. Advantages Can reason abstractly about code Can map a BitSet to a BitSet without typing “toBitSet” Spokespicture Slightly Caricatured // Fancy, we get a Bitset back! Scala Collections - BitSet Bitset is a common base class for mutable and immutable bitsets. An extra boolean for the lazy val init status bumps to 32 bytes. you may want to add a String to a BitSet and get in return a plain Set[Any]), so the above works only as long as there is a builder available that can build the new collection. You can see the performance characteristics of some common operations on collections summarized in … Since the compiler performs type checking at compile time instead of runtime, it lets the developer notice and resolve errors at the compile time itself. Hi, A stream is a lazy list as it evaluates elements only when it needs to. Understanding the performance of Scala collections classes. That’s often the primary reason for picking one collection type over another. Partially solves scala/bug#11418. scala> val stream=177#::199#::69#::Stream.empty stream: scala.collection.immutable.Stream[Int] = Stream(177, ?) HashSet implements immutable sets and uses hash table. Scala Interview Questions for Experienced – Q. Sign in This is only supported directly for mutable sequences. Partially solves scala/bug#11418. We could let BitSet.fromArray make a copy of the data and keep the BitSetN Review for performance and Java/Java 8/Guava best practices. Vectors allow accessing any element of the sequence in “effectively” constant time. The previous explanations have made it clear that different collection types have different performance characteristics. In my enumeration objects, I have to have code like this: Q.21. Immutable sets offer methods to add or remove elements by returning new Sets, as summarized in below. Adding a new element to a set or key/value pair to a map. The operation is linear, that is it takes time proportional to the collection size. books i’ve written. Bitsets are sets of non-negative integers and are represented as variable-size arrays of bits packed into 64-bit words. src/library/scala/collection/BitSet.scala, test/junit/scala/collection/mutable/BitSetTest.scala. … Method Overriding in Scala is identical to the method overriding in Java but in Scala, the overriding features are further elaborated as here, both methods as well as var or val can be overridden. Adding an element and the end of the sequence. Scala List class … Scala Interview Questions for Experienced – Q. @viktorklang thanks for your suggestions! Maybe use a ScalaCheck test instead of manually coming up with corner cases? I think the following should work (but please do test first). Collections in Scala: Advanced Collections in Scala: Advanced Pranjut Gogoi & Bhavya Aggarwal Knoldus Software LLP Scala Set is a collection of pairwise different elements of the same type. Removing an element from a set or a key from a map. We’ll occasionally send you account related emails. We use optional third-party analytics cookies to understand how you use GitHub.com so we can build better products. 12,13,14,15,16,17,18,19. Add Beam.sendBatch (returns a BitSet of successes), fixes #56. 12,13,14,15,16,17,18,19. Following questions have been asked in GATE CS 2008 exam. IMHO, while "prior art" is a fair enough reason, there is no reason not to "clean" it along the way, unless it defeats performance of course. Might a scala equivalent to bitvector be … Does a minor tweaked solution like the following offer any benefits performance-wise? You want to add an element of type B to your collection with elements of type A, however the addition of an element of type B may not be supported (e.g. They provide constant-time access to their first element as well as the rest of the list, and they have a constant-time cons operation for adding a new element to the front of the list. they're used to gather information about the pages you visit and how many clicks you need to accomplish a task. I'm not sure which underlying type would be faster, if anyone (i.e. java.util.BitSet uses long. @viktorklang me neither, but I feel similar about tailrec method that does side effects :) Scala Interview Questions for Freshers – Q. Already on GitHub? Due to a performance profiling hotspot detailed here, I implemented my own BitSet using Java's BitSet.This is intended to replace the Enumeration.ValueSet.However, it's a bit awkward to use, primarily due to my likely misunderstanding of the relationships between the Enumeration class, Enumeration type and concrete Enumeration object.. Add Beam.sendBatch (returns a BitSet of successes), fixes #56. When choosing a collection for an application where performance is extremely important, you want to choose the right Scala collection for the algorithm.. This is the main reason for aligning vavr to Scala. Given a set of n positive integers,… A 10x performance difference is a lot! a is quite regular with 2 full words. That’s often the primary reason for picking one collection type over another. Likewise, s -= elem removes elem from the set, and returns the mutated set as a result. Cache hashcode and size on a BitSet library:collections performance #9004 opened May 22, 2020 by mkeskells • Approved 2.12.14 Successfully merging this pull request may close these issues. Sign up for a free GitHub account to open an issue and contact its maintainers and the community. The previous explanations have made it clear that different collection types have different performance characteristics. Suggestions cannot be applied while the pull request is closed. Any hints would be highly appreciated. The operation takes time proportional to the logarithm of the collection size. It will be sufficient to add one import to reach 90% of vavr’s API. Showing Scaladoc and source code in the Scala REPL. The operation takes (fast) constant time. java.lang.String just forgoes the performance optimization of hash code caching when it is 0. s: scala.collection.immutable.BitSet = BitSet(0, 64, 128) scala> a(0) = 2l. This lazy computation enhances program performance. Solution If we go for the same approach here, adding a cache of hashcode to BitSet1 would keep its current footprint of 24 bytes (the var int fits in the padding gap, according to JOL). Scala combines object-oriented and functional programming in one concise, high-level language. Also: Deprecate Beam.propagate Make Tranquilizer's MessageDroppedException a singleton Improve ClusteredBeam tests and add tests involving dropping events Parallelization support: Method calls do not change. As I'm not that familiar with the Scala API as i liked to be, I'm curious if there's already a solution to this problem within scala's API which would help me solve the issue. The operation takes effectively constant time, but this might depend on some assumptions such as maximum length of a vector or distribution of hash keys. s: scala.collection.immutable.BitSet = BitSet(0, 64, 128) scala> a(0) = 2l. Programs can be written in Scala in any of the … Add this suggestion to a batch that can be applied as a single commit. JNI bindings for Zstd native library that provides fast and high compression lossless algorithm for Zstd-jni version uses the base Zstd version with Zstd-jni release appended with a dash, e. jni (4) journals A better compressed bitset in Java. In other words, a Set is a collection that contains no duplicate elements. Benchmarks (spacing is the number of 0s between 1s, so spacing = 0 is 11111..., spacing = 1 is 101010..., etc.). In C, these might be implemented using a bitvector. Showing Scaladoc and source code in the Scala REPL. We could let BitSet.fromArray make a copy of the data and keep the BitSetN std::bitset does overload the << & >> operators, but using these will result in an ASCII encoded file (i.e. I've seen a few questions on Stack Overflow relating to this, such as this question , but it seems there is no standard or easy way to do bitset I/O. Inserting an element at an arbitrary position in the sequence. Selecting the first element of the sequence. BitSet A set of “non-negative integers represented as variable-size arrays of bits packed into 64-bit words.” ... Understanding the performance of Scala collections classes. Q.21. Millions of developers and companies build, ship, and maintain their software on GitHub — the largest and most advanced development platform in the world. to your account. The previous explanations have made it clear that different collection types have different performance characteristics. Scala List class … In my enumeration objects, I have to have code like this: :). We use optional third-party analytics cookies to understand how you use GitHub.com so we can build better products. Scala's static types help avoid bugs in complex applications, and its JVM and JavaScript runtimes let you build high-performance systems with easy access to huge ecosystems of libraries. Elements insertion order is not preserved. which can be used to run Scala programs without installing. Scala Interview Questions for Freshers – Q. GitHub is home to over 50 million developers working together to host and review code, manage projects, and build software together. You can see the performance characteristics of some common operations on collections summarized in … Suggestions cannot be applied on multi-line comments. Understanding the performance of Scala collections classes. That's often the primary reason for picking one collection type over another. Also: Deprecate Beam.propagate Make Tranquilizer's MessageDroppedException a singleton Improve ClusteredBeam tests and add tests involving dropping events Producing a new sequence that consists of all elements except the first one. For immutable sequences, this produces a new sequence. How to manually declare a type when creating a Scala collection instance. Adding an element to the front of the sequence. In October of 2015 Martin Odersky asked for strawman proposals for a new collections library design for Scala 2.13, which eventually led to the project that we are currently working on, based on his latest proposal. Almost all tests are based on a, the only exception being the one with BitSet(0). Nice idea. How to manually declare a type when creating a Scala collection instance. Principles¶. Suggestions cannot be applied from pending reviews. This might not matter, but it very well might be worth it in places where performance matters. Testing whether an element is contained in set, or selecting a value associated with a key. Cache hashcode and size on a BitSet library:collections performance #9004 opened May 22, 2020 by mkeskells • Approved 2.12.14 Scala BitSet implemented with Java BitSet, for use in Scala Enumerations to replace ValueSet Due to a performance profiling hotspot detailed here, I implemented my own BitSet using Java's BitSet . Our efforts for the next release concentrate on adding more syntactic sugar and missing persistent collections beyond those of Scala. For more information, see our Privacy Statement. This suggestion has been applied or marked resolved. {0,1} = 1 byte), which is ~8x bigger than it would be if using a bit-for-bit encoding. Mutable sets offer in addition methods to add, remove, or update elements, which are summarized in below. Have a question about this project? You can see the performance characteristics of some common operations on collections summarized in … java.lang.String just forgoes the performance optimization of hash code caching when it is 0. Besides += and -= there are also the bulk operations ++= and --= which add or remove all elements of an iterable or an iterator.. The operation s += elem adds elem to the set s as a side effect, and returns the mutated set as a result. (Array[Array[BitSet]]). For a Scala developer that signature makes sense. A comment unrelated to scala: you should really be packing each base as two consequtive bits, it's crazily wasteful not to. Beginning with Scala Programming. I'm not sure which underlying type would be faster, if anyone (i.e. I've optimized my code under this assumption, making sure that just one comparison is done in those cases. This is a BitSet wrapper class to act as a Sieve abstraction for a prime calculator. For mutable sequences it modifies the existing sequence. You must change the existing code in this line in order to create a valid suggestion. We use essential cookies to perform essential website functions, e.g. Some invocations of the operation might take longer, but if many operations are performed on average only constant time per operation is taken. Improves performance of BitSet.iterator by utilising Long.numberOfTrailingZeros (instead of iterating through all integers in range and checking their presence in the BitSet). 11,20. I was wondering how you get away with only storing the current word but no index into it until I saw this. scala> s res1: scala.collection.immutable.BitSet = BitSet(1, 64, 128) I suppose it makes sense to keep this implementation around for performance reasons but I'd prefer to hide it better. Benchmarks (spacing is the number of 0s between 1s, so spacing = 0 is 11111..., spacing = 1 is 101010..., etc.). BitSet A set of “non-negative integers represented as variable-size arrays of bits packed into 64-bit words.” ... Understanding the performance of Scala collections classes. That's often the primary reason for picking one collection type over another. Note: This is an excerpt from the Scala Cookbook (partially re-worded and re-formatted for the internet). Vector is a collection type that provides good performance for all its operations. Only one suggestion per line can be applied in a batch. A Listis a finite immutable sequence. Programming in Scala: Since the Scala is a lot similar to other widely used languages syntactically, it is easier to code and learn in Scala. An extra boolean for the lazy val init status bumps to 32 bytes. Applying suggestions on deleted lines is not supported. You can always update your selection by clicking Cookie Preferences at the bottom of the page. Suggestions cannot be applied while viewing a subset of changes. You can see the performance characteristics of some common operations on collections summarized in the following two tables. byte, int, long). This is Recipe 10.4, “Understanding the performance of Scala collections.” Problem. Lazy evaluation: Allows to delay the transformation operations and thus to calculate or store only if necessary. How to manually declare a type when creating a Scala collection instance. jar lz4-java-1. they're used to log you in. There will be new persistent collections BitSet, several MultiMaps and a PriorityQueue. A comment unrelated to scala: you should really be packing each base as two consequtive bits, it's crazily wasteful not to. Improves performance of BitSet.iterator by utilising Long.numberOfTrailingZeros (instead of iterating through all integers in range and checking their presence in the BitSet). Zstd Zstd Zstd. Due to a performance profiling hotspot detailed here, I implemented my own BitSet using Java's BitSet.This is intended to replace the Enumeration.ValueSet.However, it's a bit awkward to use, primarily due to my likely misunderstanding of the relationships between the Enumeration class, Enumeration type and concrete Enumeration object.. @diesalbla your implementation seems to be correct, but it is slightly slower in most cases: hasNext is normally invoked twice for each advancement of the iterator (once directly from client code, and once from next()), and in most invocations it does not enter the while loop. WARNING: FOLLOWING CODE HAS NEVER BEEN COMPILED. Prove that Scala is a language statically/strongly typed. Learn more, We use analytics cookies to understand how you use our websites so we can make them better, e.g. Many other operations take linear time. The smallest element of the set, or the smallest key of a map. Vectors are a useful "default" data structure to reach for, but if it's at all possible, working directly with Lists or Arrays or mutable.Buffers might have an order-of-magnitude less performance overhead. ... For example, the bit set containing 3, 2, and 0 would be represented as the integer 1101 in binary, which is 13 in decimal. Can we have some tests with holes in the data or data that does not begin and end on a full word? As I'm not that familiar with the Scala API as i liked to be, I'm curious if there's already a solution to this problem within scala's API which would help me solve the issue. You could wrap this on a BitSet, it should be fine. The subset-sum problem is defined as follows. This suggestion is invalid because no changes were made to the code. As additional information: My program intialises an array of bitmaps, which are seen as an array of BitSet. For mutable sequences it modifies the existing sequence. If we go for the same approach here, adding a cache of hashcode to BitSet1 would keep its current footprint of 24 bytes (the var int fits in the padding gap, according to JOL). By clicking “Sign up for GitHub”, you agree to our terms of service and A bitset is an array of bool but each Boolean value is not stored separately instead bitset optimizes the space such that each bool takes 1 bit space only, so space taken by bitset bs is less than that of bool bs[N] and vector bs(N).However, a limitation of bitset is, N must be known at compile time, i.e., a constant (this limitation is not there with vector and dynamic array) The solution is simple: introduce some boilerplate by hoisting the code out into a named type. Furthermore, we’ve all along been imposing a significant performance penalty by using reflection. 1. Learn more. Scala Collections - BitSet Bitset is a common base class for mutable and immutable bitsets. @linasm I'm not a fan of return in Scala as it breaks last-expr-is-the-result assumptions. I've tried benchmarking the suggested implementation, and it really gives a nice further improvement: However, you helped me realize what can be improved in my implementation, and I was able to get basically the same (within ±1% margin) improvements, with less (and arguably simpler) code (updated the PR): Please let me know what you think, thanks. For immutable sequences, this produces a new sequence. This was not the first redesign for the Scala collections. Conclusion The operation takes amortized constant time. (Array[Array[BitSet]]). The entries in these two tables are explained as follows: The first table treats sequence types–both immutable and mutable–with the following operations: The second table treats mutable and immutable sets and maps with the following operations: The sequence traits Seq, IndexedSeq, and LinearSeq, Conversions Between Java and Scala Collections. Design patterns and beautiful views. How to manually declare a type when creating a Scala collection instance. 11,20. The previous explanations have made it clear that different collection types have different performance characteristics. scala> BitSet(1, 2, 3) map (_.toString.toInt) res0: BitSet = BitSet(1, 2, 3) ! Prove that Scala is a language statically/strongly typed. byte, int, long). Flags will be recomputed often, and read extremely often, so read/write performance are both important. privacy statement. Memory is also a factor, since there might be several million objects with all flags. java.util.BitSet uses long. As additional information: My program intialises an array of bitmaps, which are seen as an array of BitSet. You could wrap this on a BitSet, it should be fine. Finding a Compiler: There are various online IDEs such as GeeksforGeeks IDE, Scala Fiddle IDE etc. You signed in with another tab or window. Any hints would be highly appreciated. Can you add the benchmark code under test/benchmarks? Since we don’t need the second element yet, Scala doesn’t evaluate it. Before submitting this change, I saw return from while all over BitSet implementation: scala/src/library/scala/collection/BitSet.scala, scala/src/library/scala/collection/mutable/BitSet.scala, @linasm I think "prior art" is a valid argument. Design patterns and beautiful views.

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