BUG: Fix order='K' behavior for tobytes

[anirudh2290]

Simplify PyArray_ToString to call PyArray_Ravel internally.
This addresses #16569 (see also: #16291 (comment))

[anirudh2290]

not sure if we need this here just as a micro opt or if there is a deeper reason ?

[anirudh2290]

would appreciate input on a better name here.

[seberg]

Sorry, I see I misjudged this a bit. The current algorithm uses an iterator while ravel would create a copy if this is not already contiguous. I think the safer way might be to:

1. Fast-path when the contiguity is correct (this is the first if and is already correct).
2. Calling ravel will work, but may create an additional copy unfortunately (I somewhat expected we do that anyway, but we don't...), its just one copy more though, maybe we should not care too much...

Avoiding the second copy, can be done by either using the new iterator:

/* no need to handle empty (always contiguous) */
flags = NPY_ITER_READONLY | NPY_ITER_GROWINNER | NPY_ITER_EXTERNAL_LOOP | NPY_ITER_DONT_NEGATE_STRIDES;
iter = NpyIter_New(op,,
                    order, NPY_NO_CASTING, NULL);

prepare_things;
do inner-loop {
    memcpy();
while (iternext())

although that is a bit annoying, but if you would like to get to know that iterator API maybe not a bad exercise.

[seberg]

Or maybe we just put the axis-reorganizing ravel does into an internal helper, so that we do not have to duplicate it.

[anirudh2290]

i was a bit confused about the needs api stuff and the macros for NPY_BEGIN_THREADS_DEF , NPY_BEGIN_THREADS_NDITER etc. My understanding is that we just want to hold the GIL and I wasn't sure if we need any of this stuff.

[shubham11941140]

This will give a wrong result as LHS = 2 whereas the RHS = 3.
When the order of 'x' will be in K, then the tobytes function should hold.

[shubham11941140]

This will give a wrong result as LHS = 2 whereas the RHS = 3.
When the order of 'x' will be in K, then the tobytes function should hold.

[seberg]

The test looks correct to me. If it fails, the code needs fixing, not the test.

[charris]

@anirudh2290 Needs a rebase. Do you want to pursue this?

[anirudh2290]

Hi @charris, I won't be able to pursue this in the near future, feel free to close/reassign.