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PinnedArrays in API examples
PinnedArrays in API examples
Hello everyone!
Quick question: In the API examples for the 2000A-Series (possibly others, that's the one I know so far
) the arrays passed to the GetValues and GetTimesAndValues methods are pinned (PinnedArray) and have to be fully initialized beforehand.
Why is this necessary and in what situation would it become problematic if not using a pinned array?
Does it have performance/speed implications?
I am using GCLatencyMode.Batch and did not have any trouble so far.
Quick question: In the API examples for the 2000A-Series (possibly others, that's the one I know so far
) the arrays passed to the GetValues and GetTimesAndValues methods are pinned (PinnedArray) and have to be fully initialized beforehand. Why is this necessary and in what situation would it become problematic if not using a pinned array?
Does it have performance/speed implications?
I am using GCLatencyMode.Batch and did not have any trouble so far.
Re: PinnedArrays in API examples
You need to use pinned arrays because you are passing these from your managed code to an unmanaged C++ dll, and their location in memory needs to be fixed so that the dll can safely write to the space.
Martyn
Technical Support Manager
Technical Support Manager
Re: PinnedArrays in API examples
Hey Martyn, thanks for the answer!
I am using unpinned arrays for a while and have not encountered a problem even once.
So I am wondering now, how one would go about writing tests for this scenario
But that's a question for a different forum, I guess
BTW, the quality of your products is immensely appreciated.
I am using unpinned arrays for a while and have not encountered a problem even once.
So I am wondering now, how one would go about writing tests for this scenario
But that's a question for a different forum, I guess
BTW, the quality of your products is immensely appreciated.
Re: PinnedArrays in API examples
for C# you
use a function that allocate 250 array's of random length between 200000 and 300000 integers and write them all with some number not 0
Then exit this function.
Then call this function 100 more times.
So you C# have some cleaning up to do.
Benno
use a function that allocate 250 array's of random length between 200000 and 300000 integers and write them all with some number not 0
Then exit this function.
Then call this function 100 more times.
So you C# have some cleaning up to do.
Benno
Re: PinnedArrays in API examples
Hi bennog!
Interesting idea. If I understand correctly, I would write a C function that does 'something' (like iterating, maybe) over the arrays, and that function, should start to see discrepancies, right?
If I put increments of 1 in the arrays and check on the C side, data would get discontinous.
Thanks for the answer.
Interesting idea. If I understand correctly, I would write a C function that does 'something' (like iterating, maybe) over the arrays, and that function, should start to see discrepancies, right?
If I put increments of 1 in the arrays and check on the C side, data would get discontinous.
Thanks for the answer.
Re: PinnedArrays in API examples
it is only needed where you use managed code like C# that use garbage collect.
And if you fragment the memory on C# and allocate and release a lot of various memory sizes, C# has the nasty habit of moving memory around to different physical addresses. So unmaaged code writes to the wrong addresses.
If you use C or C++ there is no need because these don't have a garbage collect, even C++ smart pointers do not shuffle memory around.
Benno
And if you fragment the memory on C# and allocate and release a lot of various memory sizes, C# has the nasty habit of moving memory around to different physical addresses. So unmaaged code writes to the wrong addresses.
If you use C or C++ there is no need because these don't have a garbage collect, even C++ smart pointers do not shuffle memory around.
Benno
Re: PinnedArrays in API examples
That explains why I have no problems so far, without using the pinned arrays. The GC mode GCLatencyMode.Batch basically disables the GC
Re: PinnedArrays in API examples
Remember Murphy's law
https://en.wikipedia.org/wiki/Murphy%27s_law
That is all I want to add at this moment, in my experience most times sooner than later, at a moment you can not use it.
Benno
https://en.wikipedia.org/wiki/Murphy%27s_law
That is all I want to add at this moment, in my experience most times sooner than later, at a moment you can not use it.
Benno
Re: PinnedArrays in API examples
I'm curious what the decision was, not to use the "fixed" statement here, as it would make "unpinning" of the arrays unnecessary and we could just use regular GC routines.
Re: PinnedArrays in API examples
Probably because fixed keyword only works in unsafe code.
unsafe code makes some programmers scared.
https://docs.microsoft.com/en-us/dotnet ... -statement
And fixed uses pinned do do there job so it also adds an extra layer on top of pinned.
Bemmp
unsafe code makes some programmers scared.
https://docs.microsoft.com/en-us/dotnet ... -statement
And fixed uses pinned do do there job so it also adds an extra layer on top of pinned.
Bemmp
Re: PinnedArrays in API examples
Ah yes, the unsafe-scare 
I totally forgot about that. Good point…
But as I understood it, there's actually more difference between pinning via GCHandle and fixed segments. THE Hans Passant has an interesting answer over at SO, but I am not knowledgeable enough about GC internals to fully grasp it.
I totally forgot about that. Good point…But as I understood it, there's actually more difference between pinning via GCHandle and fixed segments. THE Hans Passant has an interesting answer over at SO, but I am not knowledgeable enough about GC internals to fully grasp it.
Re: PinnedArrays in API examples
I mostly 99% program in C / C++ and only for GUI stuff I use C#
So my C# answers are from some experience but not a lot I guess about 1 or 2k hours in my whole programming history.
Benno
So my C# answers are from some experience but not a lot I guess about 1 or 2k hours in my whole programming history.
Benno
Re: PinnedArrays in API examples
Is not using pinned arrays the reason why one might get the CallbackOnCollectedDelegate error?