NF - Added cython utility functions

[gabknight]

Utility functions for PTT tracking PR #2596.

Is there a good way to add unit tests on these?

[skoudoro]

Thanks @gabknight,

For the test, you can create a test_fast_numpy.py in utils/tests folder.

Inside the tests, check if np.dot is slower than your function and obtain the same result

[gabknight]

ok, thanks. I needed to change the function declaration from cdef to cpdef for the tests. Cross is 25x faster, dot is 1.5x on the length-3 vectors. There will more gain when doing the tracking in c.

[codecov]

Codecov Report

Merging #2716 (9393354) into master (551fa1c) will increase coverage by 0.00%.
The diff coverage is n/a.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #2716   +/-   ##
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  Coverage   83.83%   83.83%           
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  Files         131      131           
  Lines       18292    18293    +1     
  Branches     2979     2980    +1     
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+ Hits        15335    15336    +1     
  Misses       2220     2220           
  Partials      737      737           

Impacted Files	Coverage Δ
dipy/tracking/streamline.py	93.83% <0.00%> (+0.02%)	⬆️

[skoudoro]

Just waiting for the CI to finish and this PR is ready to be merged.

Thank you @gabknight

[skoudoro]

SMALL NOTE

We need a system to allow pytest to run test on cdef files. In this file, cpdef are used just for the tests. This is not necessary. I suppose we need test as pyx files. Something to explore