A port of NumPy to .Net

History:

In early 2018, I was tasked with porting a python/numpy application to .NET. There was no documentation available on the python source and I needed to produce binary compatible output.

I started out by trying to write custom code to do the numpy manipulations but that quickly became too difficult, so I searched for any solution that would allow .NET to perform numpy operations. I ran across this public repository.
I believe it is an abandoned effort to wrap the underlying C based numpy code in .NET interop code. It was originally worked on by Enthought Corporation under contract to Microsoft. I am not sure of the reasons, but this project was abandoned before it was finished. I was not able to figure out how to use this repository in any way, but that may have been user error on my part.

https://github.com/numpy/numpy-refactor

My initial goal was to review this source for some tips on how the numpy manipulations were done so that I could use it in my custom code.

I was getting desperate, so on a whim, I grabbed a couple of the C functions and tried to port them to C#. Generally, I did a global replace of NULL to null nd -> to . and then had to convert pointers to class references and for the most part it compiled. I slowly converted the dozens of C macros to C# functions.
Eventually I was able to get something to work so I started doing a few more functions. Before long I had most of the C code ported into a .NET DLL.

Next, I took the C# code from this repository and tried to connect it to this newly ported DLL. This involved unwinding the enormous amount of C interop code that the Enthought team wrote. Since both the DLL and higher layer library were now in C#, lots of things became simpler and it became easy to step through the code and debug it. It took several months to port this code and make it work correctly.

I ported enough of this code to complete my original porting task and then I added many more functions to help complete the testing. As a result, I believe I have a pure .NET numpy whose core logic is largely complete and correct.

Cool features:

python is a scripted language and C# is compiled language. Much of the numpy syntax is not compilable in C#, especially the slicing syntax. As the next best thing, I turned the python slicing sytax into a string which is parsed into compatible slice values. For example:

in python, a statement like this:

index = 2
a = arr[:,:index]

becomes a C# statement like this:

ndarray a = arr[":", ":" + index.ToString()] as ndarray;

or the shortcut form where casting to ndarray is not necessary:

ndarray a = arr.A(":", ":" + index.ToString());

Unit tests:

I have unit tests in python and I have similarly named unit tests in C#. I grabbed the generated output from the python tests and assert that the C# version produces the same results.

If the unit tests in the C# code are set for ignore, it is because they currently do not work 100% correctly and need to be debugged.