The Fastest Way to Modify a List in C# | Coding Demo
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- čas přidán 10. 05. 2024
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LINQ is too slow to be of use when modifying lists/arrays, and for loop is not applicable to both, nor is it the fastest either. Watch this demo and learn how to modify contents of an array and a list uniformly, and still with running time that is way below other methods.
In this demo, we will measure performance of iterating through an array and through a list, using common for loop, a LINQ expression, and a span. The rest of the demo is dedicated to measuring performance of operations that mutate content of an array or a list.
Each experiment is followed by a benchmark and explanation of the results gathered by running the benchmark. Eventually, spans will be a clean winner in all respects: execution speed, minimum memory footprint, random access to memory locations, universal support for arrays and lists.
And there will be more! You will learn the dangers that hide behind using a span created from a list, and how to avoid making a bug.
Chapters:
00:00 Intro
00:46 Improving iteration performance
04:02 Improving performance of modifying a list
06:14 Using a span for fast list modification
09:27 Analysis and comment on performance data
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I find spans very helpful during string manipulation, because I dont have to create new strings on the heap :)
True, string class is imposing needless overhead, and it is often paid in bulks. String manipulation was a recurring topic at the time when spans first appeared.
I really like your teaching syle and examples. I used spans on a project yesterday and I've seen the difference. Thanks a lot, you are great! 🙌🏻👏🏻
I am just about to apply spans to a large code base. I was postponing that process, because it will not be easy to complete - but with expected 50%+ reduced execution time, the decision is clear...
Great video, many thanks. Really appreciate mentions of not only the perf gains but also the potential dangers of this approach... Looking forward to the future content already!
Great and easy to understand explanation. Thanks a lot👍
Great video. Interesting insights on Spans. I'm always looking for opportunities to use them.
Legend! ❤
Thank you very much!
Great video! :)
spans are ref structs, containing a pointer to data and a length for its slice, so they allocated on stack only
interesting video, thank you sir
Great video ❤❤❤❤❤❤
very helpfull video , but other than that i am genuinely curious about your typing speed beacuse ,it looked extremly high in the video !!😄😄
What about altering properties in the items that are within the Span? That likely ok? Not removing/adding items themselves.
Span is just a reference to an array. It doesn't cause reallocation of the array, but only gives you access to the elements. In that light, only getting or setting the values through the span does not cause any issues.
Good video! This may be a stupid question, but how does creating a Span from a list not allocate any new memory if the List is originally on the Heap but a Span is always on the Stack? I may have misunderstood something (probably), but could you briefly explain what happens during that "conversion"? Is the List copied from the Heap to the Stack or is the Span on the Stack just referencing memory on the Heap?
You have some good questions here, and I will try to give a short answer. Nevertheless, I would suggest that you read the documentation for spans very carefully.
Span is a struct on the stack which only references (inside!) An array on heap. That prevents collection of the array and lets you perform optimized operations using that span, faster than using regular access.
There are many consequences. One is that changing the list may cause the list object to reference a new array in memory while span still holds the old one. You may think you are modifying the list, but you are not. As soon as the span goes out of scope, the old array will be subject to collection.
@@zoran-horvat Thank you for the quick answer :) So a Span is simply a struct containing pointers and basic logic for reading (and modifying) already allocated memory through references? If I understand correctly :D I will read up on spans!
i don't understand listofspan transform.. and whre is the actual implementation?
cant use CollectionsMarshall