data division only works if len(trajectory)%n_parts==0

[v9lgraf]

sites = SitesData(
    structure=s,
    trajectory=trajectory,
    floating_specie='Li',n_parts=10
)

Executing the code above throws an error.

This is resolved by instead running:

sites = SitesData(
    structure=s,
    trajectory=trajectory,
    floating_specie='Li',n_parts=6
)

Note that len(trajectory) == 12378. The error is resolved because 12378%6 == 0.

12378%10 != 0 that's why the first code snippet throws an error

This took a while to figure out though and is not robust. This error should be anticipated. Often the MD step number is not divisible by 10

One idea to solve this is clipping some of the final frames from the trajectory so that len(trajectory)%10==0. That would at most mean the loss of 0.18 ps of simulation, that is fine considering ~100 ps are run typically. However, when such clipping occurs a warning message should be displayed saying something like"In the course of the data analysis your simulation time was shortened by 0.xx ps"

[v1kko]

Yes I agree, dropping some timesteps to make it divisible by n_parts sounds like the way to implement this.
Together with a warning message, and perhaps even a toggle to turn the warning message off: no_warn_truncate=False|True as a keyword to SitesData.

what do you think @stefsmeets ?

[stefsmeets]

Another option is to have uneven parts, e.g. for 38 with n_parts=4: 10, 10, 9, 9