Dear all, I am working with a simple Poisson equation to understand better the parallel computing. So far, according to the plot in paraview, I am able to get the same correct solution using a different number of processes. For later use, I want to access the solution data as a unique local sequential numpy array that has as components the value of the solution for each node of the mesh. I thought that u.vector().gather() is the option I need, but when I print it I get different values for each processor. Here is an example for print(uu.vector().gather()) for different N processors : N= 1 [2. 2. 2.01686578 2.02107396 2.01943246 2.02655103 2. 1.98313432 2.01309658 2.02310037 1.98056756 2. 1.97892594 1.98690342 1.97344897 1.97689964] N=2 [2. 2. 2.01686578 2.02107396 2.01943246 2.02655103 2. 1.98313432 2.01309658 2.02310037 1.98056756 2. 1.97892594 1.98690342 1.97344897 1.97689964] [2. 2. 2.01788253 2.01556306 2.02651517 2. 2.01725592 1.98544718 2.02588859 2. 2.01137299 1.98085025 1.98009714 1.9850916 1.97727273 1.98118216] N=4 [1.97689956 1.98690345 2.01309647 2.02655104 2.02310037 2. 2. 2. 1.98313422 2. 1.97892604 2.01686572 2.02107399 2.01943249 1.98056736 1.97344906] [1.97689956 1.98690345 2.01309647 2.02655104 2.02310037 2. 2. 2. 1.98313422 2. 1.97892604 2.01686572 2.02107399 2.01943249 1.98056736 1.97344906] [2. 2. 2.01788253 2. 2.01556304 2.02651515 2.01137299 1.98085017 1.98509166 1.97727273 1.98118219 1.98009727 2.01725589 2.02588851 1.98544706 2. ] [2. 2. 2.01788253 2. 2.01556304 2.02651515 2.01137299 1.98085017 1.98509166 1.97727273 1.98118219 1.98009727 2.01725589 2.02588851 1.98544706 2. ] What I would like to have is that for each processor the output coincide with the sequential solution for N=1, i.e. [2. 2. 2.01686578 2.02107396 2.01943246 2.02655103 2. 1.98313432 2.01309658 2.02310037 1.98056756 2. 1.97892594 1.98690342 1.97344897 1.97689964] Could someone please suggest how to do it? Thank you in advance, best regards, Luca Mechelli -- Luca Mechelli Wissenschaftlicher Mitarbeiter Arbeitsgruppe Numerik Fachbereich Mathematik und Statistik Universität Konstanz Fach D 198 D-78457 Konstanz Telefon: +49-(0) 7531-88-4637