Functional programming: Difference between revisions

Revision as of 21:08, 30 May 2024

Revision as of 09:00, 4 June 2024

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has the mean execution time of 4.76 nanoseconds, while the second one, in which <syntaxhighlight lang="clojure" inline>.equals</syntaxhighlight> is a direct invocation of the underlying [[Java (programming language)|Java]] method, has a mean execution time of 2.8 μs – roughly 12001700 times faster. Part of that can be attributed to the type checking and exception handling involved in the implementation of <syntaxhighlight lang="clojure" inline>even?</syntaxhighlight>, so let's take for instance the [https://github.com/samber/lo lo library] for [[Go (programming language)|Go]], which implements various higher-order functions common in functional programming languages using [[Generic programming|generics]]. In a benchmark provided by the library's author, calling <code>map</code> is 4% slower than an equivalent <code>for</code> loop and has the same [[Memory management|allocation]] profile,<ref>{{Citation |last=Berthe |first=Samuel |title=samber/lo |date=2024-04-29 |url=https://github.com/samber/lo |access-date=2024-04-29}}</ref> which can be attributed to various compiler optimizations, such as [[inlining]].<ref>{{Cite web |title=Go Wiki: Compiler And Runtime Optimizations - The Go Programming Language |url=https://go.dev/wiki/CompilerOptimizations |access-date=2024-04-29 |website=go.dev |language=en}}</ref>

One distinguishing feature of [[Rust (programming language)|Rust]] are ''zero-cost abstractions''. This means that using them imposes no additional runtime overhead. This is achieved thanks to the compiler using [[loop unrolling]], where each iteration of a loop, be it imperative or using iterators, is converted into a standalone [[Assembly language|Assembly]] instruction, without the overhead of the loop controlling code. If an iterative operation writes to an array, the resulting array's elements [[Register allocation|will be stored in specific CPU registers]], allowing for [[Time complexity|constant-time access]] at runtime.<ref>{{Cite web |title=Comparing Performance: Loops vs. Iterators - The Rust Programming Language |url=https://doc.rust-lang.org/book/ch13-04-performance.html |access-date=2024-04-29 |website=doc.rust-lang.org}}</ref>