Rounding the output of self.get_weight()

[TheRolf]

• TSPLIB 95 version: 0.7.1
• Python version: 3.7
• Operating System: Win10 x64

Description

Is there a reason all edge weights get automatically rounded? Could this be optional?
Could you please emphasise the fact that the function get_weight() returns rounded values? The documentation says it returns floats, which makes the user think the precise value is returned.

[songofroland]

I had the same issue.

Documentation suggests that this function returns float however this line rounds it up to an int.

def euclidean(start, end, round=utils.nint):
    """Return the Euclidean distance between start and end.
    This is capable of performing distance calculations for EUC_2D and
    EUC_3D problems. If ``round=math.ceil`` is passed, this is suitable for
    CEIL_2D problems as well.
    :param tuple start: *n*-dimensional coordinate
    :param tuple end: *n*-dimensional coordinate
    :param callable round: function to use to round the result
    :return: rounded distance
    """
    if len(start) != len(end):
        raise ValueError('dimension mismatch between start and end')

    square_distance = sum(d * d for d in utils.deltas(start, end))
    distance = math.sqrt(square_distance)

    return round(distance)

Should I create a PR for this?

[Matej-Chmel]

I have no idea why this hasn't been implemented yet but for now there is a workaround that anybody who stumbles upon this can use.

Before using the library, remove the rounding with this code.

import functools
import tsplib95 as tsp

tsp.distances.TYPES["EUC_2D"] = functools.partial(tsp.distances.euclidean, round=lambda x: x)

Similar fix can be applied to other edge weight types.