The Fastest Way to Modify a List in C# | Coding Demo

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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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24 июн 2024

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Комментарии : 27

@zoran-horvat Год назад

Become a patron and get access to source code and exclusive live streams: www.patreon.com/posts/fastest-way-to-c-81380759

@leethompson1216 11 дней назад

Thanks a lot - Great explanation!

@muhammedemin6842 Год назад

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! 🙌🏻👏🏻

@zoran-horvat Год назад

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...

@michaltomorowicz596 Год назад

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!

@10199able Год назад

I find spans very helpful during string manipulation, because I dont have to create new strings on the heap :)

@zoran-horvat Год назад

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.

@Sp1tfire100 8 месяцев назад

Great and easy to understand explanation. Thanks a lot👍

@Wil_Bloodworth Месяц назад

You might want to read the Liskov Substitution Principle again as it only applies to derived/child classes not just any general substitution. Span does not inherit/derive from List so this has nothing to do with the LSP principle and you're not violating LSP with your example. Maybe Barbara watches your channel and she can comment. LOL

@zoran-horvat Месяц назад

LSP is not about classes but about types. So much about who should read the principle again. Regarding my video, I am not sure which timestamp in the video you are referring to. Before clarifying, be aware that assigning a list to a span without recreating the object makes the list a subtype of a span, quite formally. It is the same effect as what you would accomplish by defining a custom implicit cast operator without a direct subclass relationship. Any cast operation defines a subtype relationship, and implicit cast does that with full formality. Now with a lowered cynicism on your side and more seriousness, I would like to hear which timestamp in the video should cause concern.

@julianocs87 7 месяцев назад

Great video. Interesting insights on Spans. I'm always looking for opportunities to use them.

@_NguyenManhToan_ Год назад

Thank you very much!

@quantume7143 Год назад

Great video! :)

@timur2887 2 месяца назад

spans are ref structs, containing a pointer to data and a length for its slice, so they allocated on stack only

@muhammedalikhan7559 3 месяца назад

Legend! ❤

@_NguyenManhToan_ Год назад

Great video ❤❤❤❤❤❤

@mumk 3 месяца назад

interesting video, thank you sir

@kmsskyquake7330 7 месяцев назад

very helpfull video , but other than that i am genuinely curious about your typing speed beacuse ,it looked extremly high in the video !!😄😄

@matheosmattsson2811 7 месяцев назад

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?

@zoran-horvat 7 месяцев назад

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.

@matheosmattsson2811 7 месяцев назад

@@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!

@srkidd12 7 месяцев назад

What about altering properties in the items that are within the Span? That likely ok? Not removing/adding items themselves.

@zoran-horvat 7 месяцев назад

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.