[BUG] - Navier Stokes solver hangs in parallel if the domain has negative coordinates

[jcgraciosa]

Describe the bug

• What is the bug?
  The Navier-Stokes solver hangs during solve when run in parallel if the domain has negative coordinates. This is the root of Salam's reported issue in Kaiju.
• What version of the code?
  Latest development branch
• What system are you running the code on?
  Can be replicated in a local Mac installation or in Kaiju
• Steps to reproduce?
  This stripped version of Couette flow can be used to replicate the issue:

import sympy
import underworld3 as uw

Re         = 100
resolution = 16
U_wall     = 1.0
rho        = 1.0
nu         = 1.0 / Re
mu         = rho * nu

width       = 4.0
height      = 1.0

# will cause solve() to hang
minX, maxX  = -width/2., width/2.
minY, maxY  = -height/2., height/2.

# will NOT cause solve() to hang
#minX, maxX  = 0., width
#minY, maxY  = 0., height
#minX, maxX  = 1., 1. + width
#minY, maxY  = 0.5, 0.5 + height

uw.pprint(minX, minY)
uw.pprint(maxX, maxY)

mesh = uw.meshing.UnstructuredSimplexBox(
    minCoords=(minX, minY),
    maxCoords=(maxX, maxY),
    cellSize=1. / resolution,
    qdegree=3,
    regular=False,
)
mesh.dm.view()

v = uw.discretisation.MeshVariable("U", mesh, mesh.dim, degree=2)
p = uw.discretisation.MeshVariable("P", mesh, 1, degree=1, continuous=False)

ns = uw.systems.NavierStokesSLCN(
    mesh, velocityField=v, pressureField=p, rho=rho, order=1
)
ns.constitutive_model = uw.constitutive_models.ViscousFlowModel
ns.constitutive_model.Parameters.viscosity = mu
ns.bodyforce = sympy.Matrix([0, 0])

ns.add_dirichlet_bc((U_wall, 0.0), "Top")
ns.add_dirichlet_bc((0.0,   0.0), "Bottom")

ns.tolerance = 1.0e-6

ns.petsc_options["snes_monitor"] = None
ns.petsc_options["snes_converged_reason"] = None
ns.petsc_options["ksp_monitor"] = None

dx = mesh.get_min_radius()
dt_adv = 1.0 * dx / U_wall
dt_diff = 1.0 * dx**2 / nu
dt = min(dt_adv, dt_diff)

uw.pprint(f"dt: {dt}")

ns.solve(timestep=dt, zero_init_guess=True)

The issue appears with at least 3 procs:

pixi run mpirun -n 3 python3 couette-stripped.py