Panic in RegionAssembly reproducibly

[frehberg]

Occasionally (1:8) I observe a panic condition. I managed to print out the data of RegionAssembly causing the panic, and using this data to create a regression test (see PR)

Code with regresssion test assembling 3668 segments/lines #1126

The panic occures in the the check in file assembly.rs

            debug_assert!(num_segments % 2 == 0, "assembly segments must be eulierian");

The execution path leading to this point of the RegionAssembly occures in the context of bop.sweep() in the following code

impl<T: GeoFloat> BooleanOps for MultiPolygon<T> {
    type Scalar = T;

    fn boolean_op(&self, other: &Self, op: OpType) -> MultiPolygon<Self::Scalar> {
        let spec = BoolOp::from(op);
        let mut bop = Proc::new(spec, self.coords_count() + other.coords_count());
        bop.add_multi_polygon(self, 0);
        bop.add_multi_polygon(other, 1);
        bop.sweep()
    }

Appreciating any hint why this crash occures and how to avoid the panic crash

[urschrei]

#1102, #1103, and #1104 may be related here.

[frehberg]

is the code of RegionAssembly crashing due to a bug in the algorithm, or due to bad input parameters? In case of the latter, how to prevent this?

[urschrei]

It's crashing due to a bug, and a fix is unlikely in the short term.

[frehberg]

hopefully this test #1126 can help you to reproduce the issue and fix the code

[michaelkirk]

I believe this is a dupe of #913

That issue is still open - but let's try to focus any future discussion on this bug there. Note there may be other bugs with the boolean operations - this one in particular is about the "assembly segments must be eulierian", which I believe is caused by a collapse of floating point precision.

Feel free to re-open if I'm mistaken and this represents a different bug.

[michaelkirk]

I just merged #1234 which replaces our BoolOps implementation with one backed by the i_overlay crate. This should resolve the issue you're seeing. Let us know if it recurs. You can use it now if you use the unreleased geo crate, otherwise we expect it to be part of the upcoming v0.29.0 release.