Extracting boundary values in parallel

General
1

Hi,

I am running this code using mpirun:

import dolfin as dl
from mpi4py import MPI

comm = MPI.COMM_WORLD
mesh = dl.RectangleMesh(comm,dl.Point(0,0),dl.Point(1,1),100,100)

V = dl.FunctionSpace(mesh,'CG',1)
f = dl.Expression('(1-sin(x[0]))*(1-cos(x[1]))', degree=2)

u = dl.Function(V)
u = dl.project(f,V)

out_boundary = lambda x, on_boundary: on_boundary and dl.near(x[1],1, 1E-14)

I would like to evaluate f on the out_boundary and collect this information on rank=0. The issue is that this boundary is shared among all processes. Does anyone know what is the correct way to do this?

Thank you very much for the help.

3

What you state is the easiest way to do what you require: Evaluate f on each process which contains out_boundary then communicate that information to rank 0.

4

Thank you Nate! Do you know how to check which process contains a point?

5

See, e.g., Implementation — FEniCSx tutorial

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