Packages developed or maintained

• UFL/FFC(x)/DOLFIN(x)
• DOLFINx_MPC
• scifem
• io4dolfinx (adios4dolfinx)
• fenicsx_ii
• DOLFIN(x)-adjoint
• networks_fenicsx

mesh = dolfinx.mesh.create_unit_square(comm, 10, 10)
tdim = mesh.topology.dim
tol = 1e-14

# Divide cell into three regions
tags = (4,5,8)
cell_map = mesh.topology.index_map(tdim)
num_cells_local = cell_map.size_local + cell_map.num_ghosts
markers = np.full(num_cells_local, tags[0],  dtype=np.int32)
markers[dolfinx.mesh.locate_entities(
    mesh, tdim, lambda x: x[0] <= 0.5+tol)] = tags[1]
markers[dolfinx.mesh.locate_entities(
    mesh, tdim, lambda x: x[1] <= 0.5+tol)] = tags[2]
cells = np.arange(num_cells_local, dtype=np.int32)
ct = dolfinx.mesh.meshtags(mesh, tdim, cells, markers)

# Create a piecewise constant (per region) function space
V = create_space_of_simple_functions(mesh, ct, tags)
u = dolfinx.fem.Function(V)
u.x.array[0] = 3.2
u.x.array[1] = 5.5
u.x.array[2] = 4.2
assert len(u.x.array) == 3

from scifem import closest_point_projection
points, ref_points = closest_point_projection(
    mesh,
    closest_cells,
    points,
    tol_x=1e-7,
)

Based on simplex projections^2,3,4