[SciPy-Dev] Fast Walsh–Hadamard transform for SciPy ?

[Chaman Agrawal]

Hello everyone,

Reference : Issue #8590 <https://github.com/scipy/scipy/issues/8590>

I wanted to get started with implementing FWHT so I wanted to ask few
things please help.

1) Will it be good to implement it in FFT pack or it should be in the
signal pack.

2) Can I implement it in C or Cython as I am not familiar with Fortran so I
can not implement it like FFT is implemented.

3) If I can implement it in C or Cython please give me an overview of the
structure for the implementation to help me getting started.

If there is any other suggestion/guidance that I might have forgot to ask
for,please provide it. It would be of great help.

Thankyou,
Chaman

On Fri, Mar 23, 2018 at 10:12 AM, Ralf Gommers <ralf.gommers at gmail.com>
wrote:

>
>
> On Thu, Mar 22, 2018 at 12:39 PM, Chaman Agrawal <chaman.ag at gmail.com>
> wrote:
>
>> Hello,
>>
>
> Hi Chaman, your email client seems to be misconfigured, you're starting
> new threads. Can you please have a look at changing that?
>
> Cheers,
> Ralf
>
>
>> Thanks, please send the link ,it would be good to have multiple
>> references.
>>
>> However the important part is where to implement this ,in fftpack or
>> signal as Ralf Gommers <https://github.com/rgommers> mentioned in the
>> issue page.
>>
>> Cheers,
>> Chaman
>> I have my own code for FHT if you are interested
>>
>> On Thu, Mar 22, 2018 at 2:52 PM Chaman Agrawal <chaman.ag at gmail.com <https://mail.python.org/mailman/listinfo/scipy-dev>> wrote:
>>
>> >* Issue #8590 https://github.com/scipy/scipy/issues/8590 <https://github.com/scipy/scipy/issues/8590>
>> *>>* Currently there is no implementation of Fast Walsh–Hadamard transform in
>> *>* SciPy. Although it seems that FWHT is not as general as FFT but it is
>> *>* pretty ubiquitous ,it is there is other maths and science softwares like
>> *>* MATLAB etc. .I would like to contribute towards it. Following are the
>> *>* details about it.
>> *>* Fast Walsh–Hadamard transform
>> *>>* Hadamard transform is an example of a generalized class of Fourier
>> *>* transforms. It performs an orthogonal, symmetric, involutive, linear
>> *>* operation on 2^(m) numbers. It is equivalent to a multidimensional DFT.
>> *>* Time Complexity:
>> *>>* O(nlogn) with Fast Walsh-Hadamard transform (FWHT)
>> *>* Comparison with FFT:
>> *>>* FWHT is very useful for reducing bandwidth storage requirements and
>> *>* spread-spectrum analysis. Compared to the FFT, the FWHT requires less
>> *>* storage space and is faster to calculate because it uses only real
>> *>* additions and subtractions, while the FFT requires complex values. The FWHT
>> *>* is able to represent signals with sharp discontinuities more accurately
>> *>* using fewer coefficients than the FFT.
>> *>* Some Usage examples:
>> *>>* The Hadamard transform is used in data encryption, as well as many signal
>> *>* processing and data compression algorithms, such as JPEG XR and MPEG-4 AVC.
>> *>* It is also a crucial part of Grover's algorithm and Shor's algorithm in
>> *>* quantum computing. The Hadamard transform is also applied in scientific
>> *>* methods such as NMR, mass spectroscopy and crystallography.
>> *>
>>
>>
>>
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>
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