Use rounding instead of // in convert_str_time

[DamienTOQUER]

Change integer division to rounding for str to frame conversion. Solve #137

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📚 Documentation preview 📚: https://mdacli--138.org.readthedocs.build/en/138/

[hejamu]

Thanks for catching this @DamienTOQUER! This fix would however change the floor behaviour of the code.

Example:
convert_str_time("1ps", 0.1): old = 9, PR = 10
convert_str_time("10ps", 1): old = 10, PR = 10
convert_str_time("12.7ps", 1): old = 12, PR = 13 <-- here
convert_str_time("0.5ps", 1): old = 0, PR = 0

A safer way would be to do:

return int(np.floor(np.round(val / dt, 9)))

[hejamu]

@DamienTOQUER can you add a test for this? Also feel free to add yourself to AUTHORS.rst

@PicoCentauri can you take a look at the cases above if this is now all expected behavior?

[PicoCentauri]

Thanks for this fix. I think we might fix the tests as well.

[PicoCentauri]

Merge when your are happy @hejamu

[hejamu]

@DamienTOQUER Sorry for nitpicking, just one more thing. The docs look weird now (https://mdacli--138.org.readthedocs.build/en/138/api/utils.html)

Try something like

    Notes
    -----
    If we don't use the 9 digits then the floating point behaviour of np.floor would be unstable, i.e.:

    >>> np.floor(0.9999999999999999)
    0.0

[DamienTOQUER]

The note was a bit weird in the docs, so I tried to update it to make it clearer