Hello everybody. As some people have already pointed out, after 13:50, when I'm returning a ReadOnlySpan, the ToString() on line 21 should be removed. I didn't notice because of the implicit operator. If you leave the ToString() in then you still allocate the string you return. - Keep coding
@@roflex2 strings are immutable in C#. Even if you pass down explicitly by reference your can't change the value of the string. You just point to a new string reference type
I'm a systems developer and primarily work with low-level languages like ASM, C, C++, etc., so I don't have a lot of experience on the intricate details of optimizations for managed languages. Explanations like these are invaluable and I find them immeasurably useful so I thank you very much for this.
Yeah typically managed languages have to add complex features to get the same speeds we get using lower level languages. Its a big trade off in my opinion. In those languages you usually either have to swallow performance penalties or readability penalties. In languages like c++, using a pointer isnt going to confuse anyone. So really I prefer those languages, but it is cool to learn the intricacies of these languages. In particular because I use it for a my job
C++ also introduced similar concepts as standard, and before that there were 3rd party libraries providing some kind of span. See std::string_view and std::span
My first thought was, I mean, great, but why do I get the impression that C# has a lot of tricks for solving problems caused by C# in the first place? ;) Why not just have a span method on the string that returns a readonly reference to a section of the string?
@@jeffwilson8246 This whole thread makes as much sense as watching C while only wearing a . I don't get the OP. I understand span and TimeSpan, but I don't see the pun. I am the dummy cause 40+ people saw it. Guess I need to get out of my static internal scope of thought.
If anyone else is watching this post C# 13 the bits mentioned around 12:10 are no longer accurate afaik, since the support for those things were added in in C# 13 ps. love the video, even though it is getting old, it was still very educational
When I first watched Microsoft themselves explain Span, I was lost and confused. They have a knack for making something sound way more convoluted and complex than needed when they explain new concepts. This video made it all click instantly. Thank you very much, I can't wait to start using Span in my own work.
ye microsoft love overcomplicating every single one of their examples.....they need to hire people to teach them to keep things simple. Especially for their documentation.
I'm so impressed by these explanations. Honestly, the best thing to happen for a junior dev, is to find your channel. Great explanations, very helpful videos with in-depth knowledge and analysis. Thank you, please keep doing them!!
I love these types of videos that explain the standard classes in the framework that help you write more efficent code. These are the types of things I don't stumble upon when researching how to solve a problem. I would love to see more videos like these!
To me, these are the best technical videos on the net, even though about 95 percent of them are over my head. This video, however, was worthy of getting a bowl of popcorn, sitting back and just watching. Thanks a bunch, Nick.
Thank you for this video. As Unity 2021 LTS now supports spans this gave a really good introduction and explanation on how to use them. Also the ref struct is valuable information since I have some very short lived structs for triangles and other mesh-related objects that only live for the duration of the method.
Didn't learn anything new in this, but I'm impressed by your presentation. I would have more quickly learned how Span works if this was the first video I saw about it.
if I understand this well, when you use the span, like: Readonly dateAsSpan = _dateAsText; you make a new variable called "dateAsSpan" but it's not allocating new memory for the "value" itself (in the heap), but instead just basically stores a reference, similarly when in c (normal C, not ++ or sharp) if I had a function like this void double_it(int *j) { j *=2 } using "int *j" instead of "int j" (* means that you pass by memory address reference instead of value)
When you talk about allocation, it's important to stress that span doesn't really copy the source memory on the stack. The span object itself - containing probably a starting pointer and a max size - is created on the stack.
Great explanation, Nick, yet again! Thank you for taking the time, in your very informative videos, to show us what's happening "behind the scenes". On the heap, stack, etc. 🙏🏻
hey Nick, I have been watching your videos for a while. Just want to thank you so much for the learnings I got from them. You cannot imagine how helpful you are to people like me. I am using these learnings in a software solution I am developing myself already for a year. Again, thanks!!! Andre from Portugal
Should we refer to the _Span_ Slice method's start _index_ as... *"Spandex"* ? 😜 When a (male) programmer is very good at using Span... is he "SpanKing" ? 👑 (Or even Span heh). 🤴🏻
Great vid Nick, and there's me still working in c#7, .NET 4.8 & WinForms... I'm so far behind these days, but good to see new features in c#. I just wish the company I worked for didn't work on 15-20 year old projects...
Isn't the ReadonlySpan allocating at least a copy of the string on the heap? For example, consider: string s = "123"; ReadOnlySpan span = s; Console.WriteLine(int.Parse(span.Slice(0,2))); s = "321"; Console.WriteLine(int.Parse(span.Slice(0,2))); produces: 12 12 Oh, since strings are immutable in this language, the second time we assign to »s« we actually perform a second heap allocation, and »span« can happily use the address to which »s« pointed to when »span« was defined. And some smart-pointer-like stuff.
Even before tuples you could use *out* or *ref* parameters to return multiple valuess without the need of making a new type every time. I miss both of those greatly when I have to work in java (among lots of other things).
Sure. You also can return Monad like F# Descriminated Unions. In nutshell this is the simple value containers, but technically it incapsulated multiple values indeed. Tuples is the famous example of monads.
@@Qrzychu92 If want to return two unrelated things, they belong in seperate methods entirely. If it was co-ordinates or something like that, then Tuple would be fine.
You should have maybe ran the test with a changing date every time. Strings in c# are instantiated once per instance and re-used. So "foo" in variable a and "foo" in variable b are both the same "foo" in memory. This likely will show a more realistic real world use case.
Great video. I believe application only stops (completely) for GC when using workstation GC as opposed to server GC - you should compare the differences as they are quite striking and too long to go into here.
6:15 - You could access String as an array too! But if you would try to change even just one char like that: string myString = "Hello!"; myString [0] = 'h'; // This will not be compiled! It still would allocate a whole new string. StringBuilder do not behave like that tho so you could do that: var sb = new StringBuilder("Hello!"); sb[0] = 'h';
Thank you Nick. Your videos are easy to understand, neat and to the point. I looked on your web site at the courses and wanted to know if the Dependency injection was based on a third party app. I was unable to locate a way to contact you there.
In order to make use of the Span 'value' you still need to convert it ToString(), which as you say loses the value in Span, unless the resulting string is a concatination of a bunch of Span.Slice functions. So you could take the fact that Span is basically an Array and then join them together to produce the final result.
As you can see in the pinned comment the ToString() in the method that returns a ReadOnlySpan was a mistake. You don't need it and if you don't use it you don't allocate until the final ToString()
In your last example you changed the return type but forgot to remove the ToString call from the method, negating the performance benefit. But thanks for explaining Span (and ref struct) in an understandable way; neither of those ever made sense to me until now!
Nice! I learned a new C# feature. Span look like pointers, so I'd have liked to know what would have happened if dateAsText had changed, and make sure if span really works like pointers. (: BTW i appreciate your video.
I **think** there is a little bug at the end of the video. Line 21 you are calling and returning `ToString()` As I just learned in your video, this would allocate memory on the heap requiring GC at some point. Again, this is all stuff I learned from YOU. So thank you
With respect to writing a Span to the console, I presume you can use Console.Write(char) while maintaining its benefits? Indeed, perhaps there's a built in Console.WriteLine(Span) method? (I've not checked)
There is but that wasn’t the point of the exercise. I assume that the user needs a concrete string back so I don’t break the code contract. Even the span overload does a ToString internally and allocates the string so it’s not magic
Another great video Nick! A small question - is there a way to split Span into array\list of Spans? Or actually, what is the best way to do it, without iterating by myself over the Span?
Huh, I do understand that returning the Span is advantageous but in your example you return 'yearAsText.ToString()' althought the return type is 'ReadOnlySpan'. What happened there? Some implicit conversion?
I would like to argue that stack allocations are not guaranteed, stack itself even is not guaranteed to exists, and stack alloca are just an implementation detail, that may well be changed in the future.
Stack allocations are not guaranteed by the C# language. But they are extremely predictable/deterministic in the CLR. And that will almost guaranteed never change, as it will have a massive performance impact on everything that runs on the CLR
Could someone advise, why he is talking about the stack? It seems Span or ReadOnlySpan doesn't allocate in stack? You need to use stackalloc to place something in stack first
C# is a glom of 5-7 languages. The $MSFT team implemented ALL the ideas from the typical Advanced Programming Language Design textbook into the SAME LANGUAGE.
I guess that Parse method have span override. But what is happening if we need to use method which will except string. I guess it will have implicit conversion there.
If the method needs a string then the return string will be allocated but you can prevent any potential allocation during the mid-way processing in the method, depending on the workload. Also yeah, int.Parse has a span overload, including many other things that used to accept string.
Hello everybody. As some people have already pointed out, after 13:50, when I'm returning a ReadOnlySpan, the ToString() on line 21 should be removed. I didn't notice because of the implicit operator. If you leave the ToString() in then you still allocate the string you return.
- Keep coding
Great video. But where could I check source code?
@@lipatovsa7 The source code is available to my Patreons
Thought you were just testing if we paid attention!
@@nickchapsas What would be the benefit/differences in using method(in string text) method(ref string text) ?
@@roflex2 strings are immutable in C#. Even if you pass down explicitly by reference your can't change the value of the string. You just point to a new string reference type
I'm a systems developer and primarily work with low-level languages like ASM, C, C++, etc., so I don't have a lot of experience on the intricate details of optimizations for managed languages. Explanations like these are invaluable and I find them immeasurably useful so I thank you very much for this.
Yeah typically managed languages have to add complex features to get the same speeds we get using lower level languages. Its a big trade off in my opinion. In those languages you usually either have to swallow performance penalties or readability penalties. In languages like c++, using a pointer isnt going to confuse anyone. So really I prefer those languages, but it is cool to learn the intricacies of these languages. In particular because I use it for a my job
C++ also introduced similar concepts as standard, and before that there were 3rd party libraries providing some kind of span. See std::string_view and std::span
@@minciNashu arent those features kind of just bloat though. We have void* and thats all we really need
My first thought was, I mean, great, but why do I get the impression that C# has a lot of tricks for solving problems caused by C# in the first place? ;) Why not just have a span method on the string that returns a readonly reference to a section of the string?
@@mikicerise6250Did you have a second thought?
Span is a really under-rated feature, not just for performance, but also my favourite pun in C# - TimeSpan
Spantastic pun 😉
If you have a dog... it's probably a Spaniel ? 🐕
Lately the news has been so dull I've tuned into Cspan
@@jeffwilson8246 This whole thread makes as much sense as watching C while only wearing a .
I don't get the OP. I understand span and TimeSpan, but I don't see the pun. I am the dummy cause 40+ people saw it. Guess I need to get out of my static internal scope of thought.
If anyone else is watching this post C# 13 the bits mentioned around 12:10 are no longer accurate afaik, since the support for those things were added in in C# 13
ps. love the video, even though it is getting old, it was still very educational
When I first watched Microsoft themselves explain Span, I was lost and confused. They have a knack for making something sound way more convoluted and complex than needed when they explain new concepts. This video made it all click instantly. Thank you very much, I can't wait to start using Span in my own work.
The same is true for their documentation
ye microsoft love overcomplicating every single one of their examples.....they need to hire people to teach them to keep things simple. Especially for their documentation.
I'm so impressed by these explanations. Honestly, the best thing to happen for a junior dev, is to find your channel. Great explanations, very helpful videos with in-depth knowledge and analysis. Thank you, please keep doing them!!
I love these types of videos that explain the standard classes in the framework that help you write more efficent code. These are the types of things I don't stumble upon when researching how to solve a problem. I would love to see more videos like these!
To me, these are the best technical videos on the net, even though about 95 percent of them are over my head. This video, however, was worthy of getting a bowl of popcorn, sitting back and just watching. Thanks a bunch, Nick.
I'm a senior developer with 10+ years of experience and I learn so much from your videos thanks in advance
Thank you for this video.
As Unity 2021 LTS now supports spans this gave a really good introduction and explanation on how to use them.
Also the ref struct is valuable information since I have some very short lived structs for triangles and other mesh-related objects that only live for the duration of the method.
Didn't learn anything new in this, but I'm impressed by your presentation. I would have more quickly learned how Span works if this was the first video I saw about it.
Great video. This is a topic I've been half-aware of for a while, but seeing it in context helps a lot.
if I understand this well, when you use the span, like:
Readonly dateAsSpan = _dateAsText;
you make a new variable called "dateAsSpan" but it's not allocating new memory for the "value" itself (in the heap), but instead just basically stores a reference, similarly when in c (normal C, not ++ or sharp) if I had a function like this
void double_it(int *j) { j *=2 }
using "int *j" instead of "int j" (* means that you pass by memory address reference instead of value)
When you talk about allocation, it's important to stress that span doesn't really copy the source memory on the stack. The span object itself - containing probably a starting pointer and a max size - is created on the stack.
Very true👆He should explaine it, otherwise it's misleading
As usual, you explain the nuts and bolts, the theory, and the benefits, all better than the documentation and anything else I’ve found.
this is the first explanation of Span that made sense to me.
thank you!!
Great explanation, Nick, yet again! Thank you for taking the time, in your very informative videos, to show us what's happening "behind the scenes". On the heap, stack, etc. 🙏🏻
Span is a powerful structure but has some limitation, what about Memory and what is the difference between them
hey Nick, I have been watching your videos for a while. Just want to thank you so much for the learnings I got from them. You cannot imagine how helpful you are to people like me. I am using these learnings in a software solution I am developing myself already for a year. Again, thanks!!!
Andre from Portugal
Nothing new under the sun but very well explained. It's useful to have this kind of videos around, proper knowledge should be distributed like this.
This is... I can't believe how many times this could've helped me...
Had missed the memo on this one. Thanks, this was really informative!
4:18 benchy was such a cute name 😍😂 didn't see that coming
Curious to learn how it deals with byte arrays, compared to working with strings like you demo'd.
That memory view in rider is awesome
Its nice to see that D is benefiting C#
Wow, I never see before but I will us it in the next projects -- thank you.
Should we refer to the _Span_ Slice method's start _index_ as... *"Spandex"* ? 😜
When a (male) programmer is very good at using Span... is he "SpanKing" ? 👑
(Or even Span heh). 🤴🏻
wtf
Great vid Nick, and there's me still working in c#7, .NET 4.8 & WinForms... I'm so far behind these days, but good to see new features in c#. I just wish the company I worked for didn't work on 15-20 year old projects...
don't worry, it's the same for me. Working with .Net framework 4.6.1 ! But i never stop learning new technologies. It is the only way
@@aminejadid2702 Same here, but I'm now losing interest doing it in my spare time, so unless I do it at work I lose the new skill.
Add the System.Memory Nuget package. It's not everything that you get with core, but you get some benefit.
@@harag9 You can always find a better job.
.net 4.0 for me at work 🤣
you should make a follow up video on ref structs if you haven't already.
I really appreciate your content Nick, helped me a lot improve the way i code :)
Your video's are awesome. I very much appreciate the technical in-depth explanations of them. Thanks a ton!
Isn't the ReadonlySpan allocating at least a copy of the string on the heap?
For example, consider:
string s = "123";
ReadOnlySpan span = s;
Console.WriteLine(int.Parse(span.Slice(0,2)));
s = "321";
Console.WriteLine(int.Parse(span.Slice(0,2)));
produces:
12
12
Oh, since strings are immutable in this language, the second time we assign to »s« we actually perform a second heap allocation, and »span« can happily use the address to which »s« pointed to when »span« was defined. And some smart-pointer-like stuff.
Your short brought me here. Good stuff!
wohoaaaa!!! now i understand a bit more the use span and garbage collectors....thanks nick!!
So it's like a StringView, providing a view into the string pretty much.
True
For those who are not aware - It's std::string_view (after you #include ) in C++ 17
Amazing delivery. Thank you!
**Everyone** Nice video!
**Me** Wait... A method can return multiple values?!
Tuples!
Even before tuples you could use *out* or *ref* parameters to return multiple valuess without the need of making a new type every time. I miss both of those greatly when I have to work in java (among lots of other things).
Sure. You also can return Monad like F# Descriminated Unions. In nutshell this is the simple value containers, but technically it incapsulated multiple values indeed. Tuples is the famous example of monads.
Yeah but don't. Unless they are related. Like co-ordinates or dates (you would use DateTime instead imo)
@@Qrzychu92 If want to return two unrelated things, they belong in seperate methods entirely. If it was co-ordinates or something like that, then Tuple would be fine.
Very nice explanation. Will surely be helpful in my work. Thanks!
So this is how you use memory tab in Rider!
This is excellent for string manipulations
In comparison to C- span sound like a pair of pointers, and slice moves one of them.
I hope I got the idea of this feature thanks!
You should have maybe ran the test with a changing date every time. Strings in c# are instantiated once per instance and re-used. So "foo" in variable a and "foo" in variable b are both the same "foo" in memory. This likely will show a more realistic real world use case.
Great video. I believe application only stops (completely) for GC when using workstation GC as opposed to server GC - you should compare the differences as they are quite striking and too long to go into here.
Very cool explanation! Thank you!
Brilliantly explained, as per usual.
Excellent video and presentation.
Very good video - has helped to clear up my understanding of Span :)
6:15 - You could access String as an array too!
But if you would try to change even just one char like that:
string myString = "Hello!";
myString [0] = 'h'; // This will not be compiled!
It still would allocate a whole new string. StringBuilder do not behave like that tho so you could do that:
var sb = new StringBuilder("Hello!");
sb[0] = 'h';
The indexer of a string in C# is get only.
What you wrote is invalid code.
@@Dennis19901 Thanks! I pointed out that this line can't be compiled.
Good video, very insightful !
Great Video, thanks for the board explanation, it was awesome!
Thank you Nick. Your videos are easy to understand, neat and to the point. I looked on your web site at the courses and wanted to know if the Dependency injection was based on a third party app. I was unable to locate a way to contact you there.
great example m8 ty for the presentation
Great explanation, Nick 👍
In order to make use of the Span 'value' you still need to convert it ToString(), which as you say loses the value in Span, unless the resulting string is a concatination of a bunch of Span.Slice functions. So you could take the fact that Span is basically an Array and then join them together to produce the final result.
As you can see in the pinned comment the ToString() in the method that returns a ReadOnlySpan was a mistake. You don't need it and if you don't use it you don't allocate until the final ToString()
You are amazing! Thanks for your explanations
Does int.Parse accept a Span? or theres a implicit conversion from Span back to string?
There is an overload with Span yeah
Excellent explanation, Nick! Thank you very much. :)
Marvelous ! To the point. Respect !
In your last example you changed the return type but forgot to remove the ToString call from the method, negating the performance benefit. But thanks for explaining Span (and ref struct) in an understandable way; neither of those ever made sense to me until now!
Nicely explained!
Nice! I learned a new C# feature. Span look like pointers, so I'd have liked to know what would have happened if dateAsText had changed, and make sure if span really works like pointers. (:
BTW i appreciate your video.
Hi Nick, great video as usual :)
I **think** there is a little bug at the end of the video.
Line 21 you are calling and returning `ToString()`
As I just learned in your video, this would allocate memory on the heap requiring GC at some point.
Again, this is all stuff I learned from YOU. So thank you
Aaaaaaaaaaaaaaaaaaaaaaand I just saw the pinned comment 🤦🏻♂
Oh well. Guess this shows I'm paying attention and learning stuff
With respect to writing a Span to the console, I presume you can use Console.Write(char) while maintaining its benefits? Indeed, perhaps there's a built in Console.WriteLine(Span) method? (I've not checked)
There is but that wasn’t the point of the exercise. I assume that the user needs a concrete string back so I don’t break the code contract. Even the span overload does a ToString internally and allocates the string so it’s not magic
@@nickchapsas Interesting. Would it be more efficient for the WriteLine method to not allocate a string and just repeatedly call Write(char)?
If int.Parse did not need to input string but span why Console.WriteLine need it?
Another great video Nick!
A small question - is there a way to split Span into array\list of Spans?
Or actually, what is the best way to do it, without iterating by myself over the Span?
Hi, Thanks for your great video,
Please record a view about diagnostics and tracing in .NET 5.
Great vid easy to follow thankyou
Thank you very much
Great presentation, thank you!
Span? I only know Div
Very nice and helpfully 🎉
That is a great video, thanks, Nick. May I ask what IDE you are using?
Huh, I do understand that returning the Span is advantageous but in your example you return 'yearAsText.ToString()' althought the return type is 'ReadOnlySpan'. What happened there? Some implicit conversion?
Thank you
Quality content as always !
good stuff! thanks for sharing.
I would like to argue that stack allocations are not guaranteed, stack itself even is not guaranteed to exists, and stack alloca are just an implementation detail, that may well be changed in the future.
Stack allocations are not guaranteed by the C# language.
But they are extremely predictable/deterministic in the CLR.
And that will almost guaranteed never change, as it will have a massive performance impact on everything that runs on the CLR
Nice, thanks for that!!!
Nice content!
Brilliant as usally, Nick :-)
Hi. Thank you for the tutorials. I have learned a lot. I wanted to know how do you get the results inline. Thank you.
The only problem with this is its assuming ascii strings. Handling unicode cant be done easily with a span
Actually char in C# is a UTF16 character, and strings are UTF16 as well, so this would not be a problem at all
@@viktorgustavsson341 oh interesting. Char is 16 bit. That kinda blows my mind if im being honest
Could someone advise, why he is talking about the stack? It seems Span or ReadOnlySpan doesn't allocate in stack? You need to use stackalloc to place something in stack first
Great video! short and to the point, now you should do on Memory :)
This is great.
So I wonder if there is a similar use of SPAN for a more common task of parsing CSV comma delimited strings?
Yeah that's a great usecase
Thanks from Ukraine! UA
Phenomenal!!!
The stack Size is 1MB. Will it get full?
Great video as always!
in 2:26 how do you get to that debugger window with the memory tab ?
The Span.ToString() method would allocate heap memory because strings are immutable, right?
C# is a glom of 5-7 languages. The $MSFT team implemented ALL the ideas from the typical Advanced Programming Language Design textbook into the SAME LANGUAGE.
this is brillant
perfect
Amazing
May I know which editor you are using? Thank you!
Is Span.Slice.ToArray() slightly faster than Buffer.BlockCopy or byte array copy using unsafe methods? (seems to be yes)
I guess that Parse method have span override. But what is happening if we need to use method which will except string.
I guess it will have implicit conversion there.
If the method needs a string then the return string will be allocated but you can prevent any potential allocation during the mid-way processing in the method, depending on the workload. Also yeah, int.Parse has a span overload, including many other things that used to accept string.