[ENH] Parallelize SAX and PAA transformers

[aadya940]

Related to #2972

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[hadifawaz1999]

Nice addition @aadya940 !

Could you run examples comparing the old and new code in terms of output accuracy ? to make sure the algorithm didnt change Also can we benchmark the time gain ? like see how faster it becomes as plot in function of n samples length of the series etc.

[aadya940]

@hadifawaz1999 Yes sure

[hadifawaz1999]

nothing is dead code @aadya940 :) just probably inconsistent usage of prange, but code works fine

[aadya940]

@hadifawaz1999 By dead code I meant it has no effect on the output and gives identical results in terms of speed and accuracy to if there was a single prange since numba ignores other nested prange :)

[hadifawaz1999]

@hadifawaz1999 By dead code I meant it has no effect on the output and gives identical results in terms of speed and accuracy to if there was a single prange since numba ignores other nested prange :)

if am not mistaken numba considers a prange as a normal range when its nested, so its simply useless usage of prange nested yes

[aadya940]

LGTM! The changes suggested have been made.

[aadya940]

@baraline Any updates here?

[baraline]

Will take a look tomorrow

[MatthewMiddlehurst]

The inverse is parallelised for PAA but not SAX, any reason for that?