Unable to include bitset.pxi

[Chin-Hung Lin]

Hello,

Sage version: 9.0, Release Date 2020-01-01

installed through arch linux package manager

I tried to run the code below in Jupyter

%%cython

include "sage/data_structures/bitset.pxi"

but then it returns a long list of error and I believe the most relevant one is as below.  

(If necessary, I can provide the full error message.)

Could someone help and give me some advice?  

PS I have checked that the bitset.pxi on my machine is the same as the lastest version on the develop branch.

https://github.com/sagemath/sage/blob/develop/src/sage/data_structures/bitset.pxi

RuntimeError: Error compiling Cython file:

------------------------------------------------------------

...

    """

    if size <= 0:

        raise ValueError("bitset capacity must be greater than 0")

    bits.size = size

    bits.limbs = (size - 1) / (8 * sizeof(mp_limb_t)) + 1

                                                     ^

------------------------------------------------------------

/usr/lib/python3.8/site-packages/sage/data_structures/bitset.pxi:84:54: Cannot assign type 'double' to 'mp_size_t'

[Chin-Hung Lin]

I am able to resolve the issue by modifying 

bits.limbs = (size - 1) / (8 * sizeof(mp_limb_t)) + 1

to integer division

bits.limbs = (size - 1) // (8 * sizeof(mp_limb_t)) + 1

However, I doubt that this is the correct way to fix it?  

1. If this is correct, should I send initiate a ticket to correct th code on SageMath?

2. If not, what is the better way to avoid this error?

[Dima Pasechnik]

On Sun, Feb 2, 2020 at 5:51 AM Chin-Hung Lin <jephi...@gmail.com> wrote:
>
> I am able to resolve the issue by modifying
>
> bits.limbs = (size - 1) / (8 * sizeof(mp_limb_t)) + 1
>
> to integer division
>
> bits.limbs = (size - 1) // (8 * sizeof(mp_limb_t)) + 1
>
>
> However, I doubt that this is the correct way to fix it?
> 1. If this is correct, should I send initiate a ticket to correct th code on SageMath?

this appears to be a kind of bug in the %%cython magic, which fails to
take into account
that in Python 3 '/' is no longer integer division.

I've opened a ticket - probably we need to make sure that *.pxi files
do not contain Python2-only code.
https://trac.sagemath.org/ticket/29139

> 2. If not, what is the better way to avoid this error?
>

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