using c++ code in wpf

Question

HELLO, i wish to know if there is a way to use c++ methods, performing special operations in wpf ? thank you

Vulpes · Answer

Well, I'm glad that you've managed to come up with a solution for this even if you're not sure why it didn't work before. A profiler is a tool which traces through your code and tells you how long each method took to execute, how much memory is being used and so on. This enables you to identify any performance bottlenecks in your code and, hopefully, address them. Well known profilers for .NET code include Redgate ANTS and JetBrains dotTrace.

Vulpes · Answer

I'm afraid it doesn't alter the basic problem. In fact, if it's open source, it increases the likelihood that it will be class-based unmanaged C++ which is the most difficult to access from C# code. However, if it's a popular open source library, then it's possible that somebody may have already built a .NET wrapper for it so I'd look into that before you do anything else.

Vulpes · Answer

It depends on which flavor of C++ you're talking about. If it's a COM dll, then you can use COM interop. If it's essentially a bunch of C functions, you can use P/Invoke. If it's a .NET dll written in C++/CLI, you can add a reference to it as you would with a C# dll. However, if it's a 'class-based' unmanaged C++ dll, then the only way I can think of is to write a wrapper for it using 'mixed mode' C++/CLI but only expose the .NET part. You can then add a reference to the C++/CLI dll in the usual way.

Sanju Singh · Answer

thanks vulpes. That was valuable information for me. I will read more on that.

Sanju Singh · Answer

hello Vulpes . I have made changes in the code and now it works fine. However i don't see the logic of the slow down. The methods of class 'alglib' i was calling are them self dependent on the methods from another class(with same name and functionality).what i did is just used the internally used class object and its data members. The code runs fine now. what is profiling ?

Vulpes · Answer

Have you tried profiling the code to see where the bottleneck lies?

Sanju Singh · Answer

the index gives a unique tag for each point in the kd-tree. building a kd tree is working fine. the size of the tree remains same for each iteration. when called first time loop for same size of kd-tree run for few secs but for 10+ mins when called next time.

Vulpes · Answer

The only insight I can offer is that the size and composition of the kdtree will affect the speed of this method and hence the loop: alglib.kdtreequeryaknn(kd, temp, 1, false, tolarence); and 'kd' itself is determined by this method: alglib.kdtreebuildtagged(pointCloud3, index,3,0,2,out kd); So is pointCloud3 always of a similar size each time the method is called and does the 'index' parameter have any bearing on the number of points that are being processed?

Sanju Singh · Answer

// the method is here : private void getClosestPoint2() { closestPoint.Clear(); double[,] r = new double[0, 0]; int[] tag = new int[0]; double[] temp = new double[3]; alglib.kdtree kd; alglib.kdtreebuildtagged(pointCloud3, index,3,0,2,out kd); for (int i = 0; i { temp[0] = pointCloud1[i, 0]; temp[1] = pointCloud1[i, 1]; temp[2] = pointCloud1[i, 2]; // search for the closest points alglib.kdtreequeryaknn(kd, temp, 1, false, tolarence); .... ..... closestPoint.Add(i,tag[0]); } }

Sanju Singh · Answer

vulpes i need some help here. I am using this library functions for my work. in a for loop i call a method which gives me an array of doubles.the loop runs 100,000 times on an average. the problem is that in first iteration/ function call the loop runs at normal speed how ever if called again it runs very slow ! can you tell me what can cause such situation ? your inputs will be of great value to me. thank you

Sanju Singh · Answer

Vulpes, i explored this library and looks like methods of my interest are available here. However there are some performance issues.Anyway, thanks a lot for this information.

Vulpes · Answer

There seems to be a few of these 'approximate nearest neighbor' libraries around and I've found one here which supports C#: http://www.alglib.net/other/nearestneighbors.php However, there are some performance & license limitations on the free version which might not be acceptable for the application you're developing.

Sanju Singh · Answer

ok. the library is ANN (approximate nearest neighbor) library. I searched but could not fined something parallel to it for c#. basically i want to reduce the cost of searching closest point and this library uses kd-tree which makes the operation of 0(ln(n)). If you come across something close , please inform. your inputs will be of great help. thank you. link for the library is here: http://www.cs.umd.edu/~mount/ANN/

Sanju Singh · Answer

hello Vulpes. I have a different situation. I have got an open source library which does my task. However the library is coded in c++. I compiled the code. Now how do i use this code in my wpf project ?

Vulpes · Answer

Can you post the signatures for these 4 methods - I'm not bothered about the code within them - so I can see what needs to be done to call them using P/Invoke. It's worrying me that you're calling them methods rather than functions as this suggests they're instance members of a C++ class or struct. If they are then you won't be able to use P/Invoke - you'll need to write a wrapper instead. Also, if they're not in a dll just now, you'll need to create one.

Sanju Singh · Answer

i have four methods written in a c ++ file which perform a particular operation. so, ithink i need to use th P/Invoke method. can you explain a little more how can i do this ? thank you

Sanju Singh · Answer

thanks vulpes but i have no idea of writing c++/cll wrappers.

Prasham Sabadra · Answer

Hi Sanju, Please have a look once http://www.codeguru.com/cpp/cpp/cpp_managed/general/article.php/c16355/Using-WPF-with-Managed-C.htm may this will help you.