So firedrake_0 is the object prefix of your SNES object?
> On Sep 17, 2024, at 10:37 AM, miguel.salazar <miguel.sala...@corintis.com> > wrote: > > >In my reading, it says > >Residual norms for firedrake_0_ solve. > > 0 KSP Residual norm 4.621368953027e+02 > > > so the residual in the first (0th) split does correspond to the > > outer-most KSP residual norm (not printed but equal to the SNES at the > > first iteration of Newton. > > > It is the residual norm of the first field of the first field that is 1 > > >Residual norms for firedrake_0_fieldsplit_0_ solve. > > 0 KSP Residual norm 1.000000000000e+00 > > Residual norms for firedrake_0_ solve. > 0 KSP Residual norm 4.621368953027e+02 > > Is the residual of the outer solve (it is being printed). > > Residual norms for firedrake_0_fieldsplit_0_ solve. > 0 KSP Residual norm 1.000000000000e+00 > > Is the residual of the first field. I am not sure what you are referring to > with “the residual norm of the first field of the first field” > > Thanks, > Miguel > > > > > > > MIGUEL ANGEL SALAZAR DE TROYA > Head of Software Engineering > miguel.sala...@corintis.com <mailto:miguel.sala...@corintis.com> > Corintis SA > EPFL Innovation Park Building C > 1015 Lausanne > <2024-08-1609_02_11-re_mailmigrationfromgoogletooffice365-sebastien.go...@corintis.com-co_4456a1bf-dd3e-46b7-85f9-21f278e66a79.png> > Here at Corintis we care for your privacy. That is why we have taken > appropriate measures to ensure that the data you have provided to us is > always secure. > From: Barry Smith <bsm...@petsc.dev <mailto:bsm...@petsc.dev>> > Date: Tuesday, 17 September 2024 at 16:24 > To: miguel.salazar <miguel.sala...@corintis.com > <mailto:miguel.sala...@corintis.com>> > Cc: petsc-users@mcs.anl.gov <mailto:petsc-users@mcs.anl.gov> > <petsc-users@mcs.anl.gov <mailto:petsc-users@mcs.anl.gov>> > Subject: Re: [petsc-users] Residual at the fieldsplit level > > > Initial residual: 462.13689530272404 > 0 SNES Function norm 4.621368953027e+02 > Residual norms for firedrake_0_ solve. > 0 KSP Residual norm 4.621368953027e+02 > Residual norms for firedrake_0_fieldsplit_0_ solve. > 0 KSP Residual norm 1.000000000000e+00 > 1 KSP Residual norm 3.501082228626e-15 > Residual norms for firedrake_0_fieldsplit_1_ solve. > 0 KSP Residual norm 0.000000000000e+00 > 1 KSP Residual norm 0.000000000000e+00 > 1 KSP Residual norm 1.612167203819e-12 > 1 SNES Function norm 1.599350481360e-12 > ``` > > Using the fieldsplit additive preconditioner, the problem converges in a > single KSP iteration, as expected. However, I do not understand why the > residual of fieldsplit_0 (1e+0) does not coincide with the outer residual > (462.13689530272404). It should be the case given that only fieldsplit_0 has > a non-zero residual contribution. The fact that it is just 1 is suspicious. > Is there something about how the fieldsplit works that I am missing? > > In my reading, it says > Residual norms for firedrake_0_ solve. > 0 KSP Residual norm 4.621368953027e+02 > > so the residual in the first (0th) split does correspond to the > outer-most KSP residual norm (not printed but equal to the SNES at the first > iteration of Newton. > > It is the residual norm of the first field of the first field that is 1 > > Residual norms for firedrake_0_fieldsplit_0_ solve. > 0 KSP Residual norm 1.000000000000e+00 > > Or am I missing something > > Barry > > > > > > > > Initial residual: 462.13689530272404 > 0 SNES Function norm 4.621368953027e+02 > Residual norms for firedrake_0_ solve. > 0 KSP Residual norm 4.621368953027e+02 > Residual norms for firedrake_0_ solve. > 0 KSP unpreconditioned resid norm 4.621368953027e+02 true resid norm > 4.621368953027e+02 ||r(i)||/||b|| 1.000000000000e+00 > Residual norms for firedrake_0_fieldsplit_0_ solve. > 0 KSP Residual norm 1.000000000000e+00 > Residual norms for firedrake_0_fieldsplit_0_ solve. > 0 KSP none resid norm 1.000000000000e+00 true resid norm > 3.501082228626e-15 ||r(i)||/||b|| 3.501082228626e-15 > 1 KSP Residual norm 3.501082228626e-15 > 1 KSP none resid norm 3.501082228626e-15 true resid norm > 3.501082228626e-15 ||r(i)||/||b|| 3.501082228626e-15 > Residual norms for firedrake_0_fieldsplit_1_ solve. > 0 KSP Residual norm 0.000000000000e+00 > Residual norms for firedrake_0_fieldsplit_1_ solve. > 0 KSP none resid norm 0.000000000000e+00 true resid norm > 0.000000000000e+00 ||r(i)||/||b|| inf > 1 KSP Residual norm 0.000000000000e+00 > 1 KSP none resid norm 0.000000000000e+00 true resid norm > 0.000000000000e+00 ||r(i)||/||b|| inf > 1 KSP Residual norm 1.612167203819e-12 > 1 KSP unpreconditioned resid norm 1.612167203819e-12 true resid norm > 1.589286585800e-12 ||r(i)||/||b|| 3.438995245681e-15 > 1 SNES Function norm 1.599350481360e-12 > > > > On Sep 17, 2024, at 1:04 AM, miguel.salazar <miguel.sala...@corintis.com > <mailto:miguel.sala...@corintis.com>> wrote: > > These are the new options (with ksp_monitor_true_residual) > > solver_mumps_assembled = { > "ksp_type": "preonly", > "ksp_monitor": None, > "ksp_monitor_true_residual": None, > "pc_type": "python", > "pc_python_type": "firedrake.AssembledPC", > "assembled_pc_type": "lu", > "assembled_pc_factor_mat_solver_type": "mumps", > "assembled_mat_mumps_icntl_14": 200, > "assembled_mat_mumps_icntl_24": 1, > } > solver_fieldsplit = { > "mat_type": "matfree", > "snes_monitor": None, > "snes_type": "newtonls", > "ksp_type": "fgmres", > "ksp_monitor_true_residual": None, > "ksp_rtol": 1e-1, > "ksp_monitor": None, > "pc_type": "fieldsplit", > "pc_fieldsplit_type": "additive", > "fieldsplit_0": solver_mumps_assembled, > "fieldsplit_1": solver_mumps_assembled, > } > > And this is the output > > Initial residual: 462.13689530272404 > 0 SNES Function norm 4.621368953027e+02 > Residual norms for firedrake_0_ solve. > 0 KSP Residual norm 4.621368953027e+02 > Residual norms for firedrake_0_ solve. > 0 KSP unpreconditioned resid norm 4.621368953027e+02 true resid norm > 4.621368953027e+02 ||r(i)||/||b|| 1.000000000000e+00 > Residual norms for firedrake_0_fieldsplit_0_ solve. > 0 KSP Residual norm 1.000000000000e+00 > Residual norms for firedrake_0_fieldsplit_0_ solve. > 0 KSP none resid norm 1.000000000000e+00 true resid norm > 3.501082228626e-15 ||r(i)||/||b|| 3.501082228626e-15 > 1 KSP Residual norm 3.501082228626e-15 > 1 KSP none resid norm 3.501082228626e-15 true resid norm > 3.501082228626e-15 ||r(i)||/||b|| 3.501082228626e-15 > Residual norms for firedrake_0_fieldsplit_1_ solve. > 0 KSP Residual norm 0.000000000000e+00 > Residual norms for firedrake_0_fieldsplit_1_ solve. > 0 KSP none resid norm 0.000000000000e+00 true resid norm > 0.000000000000e+00 ||r(i)||/||b|| inf > 1 KSP Residual norm 0.000000000000e+00 > 1 KSP none resid norm 0.000000000000e+00 true resid norm > 0.000000000000e+00 ||r(i)||/||b|| inf > 1 KSP Residual norm 1.612167203819e-12 > 1 KSP unpreconditioned resid norm 1.612167203819e-12 true resid norm > 1.589286585800e-12 ||r(i)||/||b|| 3.438995245681e-15 > 1 SNES Function norm 1.599350481360e-12 > > The true residual is very low. (3.501082228626e-15) > > > MIGUEL ANGEL SALAZAR DE TROYA > Head of Software Engineering > miguel.sala...@corintis.com <mailto:miguel.sala...@corintis.com> > Corintis SA > EPFL Innovation Park Building C > 1015 Lausanne > > <2024-08-1609_02_11-re_mailmigrationfromgoogletooffice365-sebastien.go...@corintis.com-co_4456a1bf-dd3e-46b7-85f9-21f278e66a79.png> > Here at Corintis we care for your privacy. That is why we have taken > appropriate measures to ensure that the data you have provided to us is > always secure. > From: Barry Smith <bsm...@petsc.dev <mailto:bsm...@petsc.dev>> > Date: Monday, 16 September 2024 at 19:34 > To: miguel.salazar <miguel.sala...@corintis.com > <mailto:miguel.sala...@corintis.com>> > Cc: petsc-users@mcs.anl.gov <mailto:petsc-users@mcs.anl.gov> > <petsc-users@mcs.anl.gov <mailto:petsc-users@mcs.anl.gov>> > Subject: Re: [petsc-users] Residual at the fieldsplit level > > > Try ksp_monitor_true_residual. Let's see if it is an issue of > preconditioned vs unpreconditioned residual. > > > > > On Sep 16, 2024, at 1:05 PM, miguel.salazar <miguel.sala...@corintis.com > <mailto:miguel.sala...@corintis.com>> wrote: > > Hello, > > I have this simple example on Firedrake to illustrate my point. I am solving > for a two-component poisson equation (uncoupled). Only the first component > has a non-zero residual. > > ``` > import firedrake as fd > from firedrake import inner, grad, dx, sin, pi > > N = 10 > mesh = fd.UnitSquareMesh(N, N) > V = fd.FunctionSpace(mesh, "CG", 1) > W = V * V > u = fd.Function(W) > v = fd.TestFunction(W) > a = inner(grad(u[0]), grad(v[0])) * dx + inner(grad(u[1]), grad(v[1])) * dx > x = fd.SpatialCoordinate(mesh) > f = fd.Function(V) > f.interpolate(fd.Constant(1e4) * sin(x[0] * pi) * sin(2 * x[1] * pi)) > L = f * v[0] * dx > F = a - L > bcs = [fd.DirichletBC(W.sub(0), fd.Constant(2.0), (1,))] > > > def snes_firedrake_residual(F, u, bcs): > for bcs_ in bcs: > bcs_.apply(u) > residual = fd.assemble(F, bcs=bcs, zero_bc_nodes=True) > with residual.dat.vec_ro as r: > print("Initial residual:", r.norm()) > > > snes_firedrake_residual(F, u, bcs) > > > problem = fd.NonlinearVariationalProblem(F, u, bcs=bcs) > solver_mumps_assembled = { > "ksp_type": "preonly", > "ksp_monitor": None, > "pc_type": "python", > "pc_python_type": "firedrake.AssembledPC", > "assembled_pc_type": "lu", > "assembled_pc_factor_mat_solver_type": "mumps", > "assembled_mat_mumps_icntl_14": 200, > "assembled_mat_mumps_icntl_24": 1, > } > solver_fieldsplit = { > "mat_type": "matfree", > "snes_type": "newtonls", > "ksp_type": "fgmres", > "ksp_rtol": 1e-1, > "ksp_monitor": None, > "pc_type": "fieldsplit", > "pc_fieldsplit_type": "additive", > "fieldsplit_0": solver_mumps_assembled, > "fieldsplit_1": solver_mumps_assembled, > } > > solver = fd.NonlinearVariationalSolver(problem, > solver_parameters=solver_fieldsplit) > solver.solve() > ``` > > The PETSc output is as follow > > ``` > Initial residual: 462.13689530272404 > 0 SNES Function norm 4.621368953027e+02 > Residual norms for firedrake_0_ solve. > 0 KSP Residual norm 4.621368953027e+02 > Residual norms for firedrake_0_fieldsplit_0_ solve. > 0 KSP Residual norm 1.000000000000e+00 > 1 KSP Residual norm 3.501082228626e-15 > Residual norms for firedrake_0_fieldsplit_1_ solve. > 0 KSP Residual norm 0.000000000000e+00 > 1 KSP Residual norm 0.000000000000e+00 > 1 KSP Residual norm 1.612167203819e-12 > 1 SNES Function norm 1.599350481360e-12 > ``` > > Using the fieldsplit additive preconditioner, the problem converges in a > single KSP iteration, as expected. However, I do not understand why the > residual of fieldsplit_0 (1e+0) does not coincide with the outer residual > (462.13689530272404). It should be the case given that only fieldsplit_0 has > a non-zero residual contribution. The fact that it is just 1 is suspicious. > Is there something about how the fieldsplit works that I am missing? > > Thanks, > Miguel > > MIGUEL ANGEL SALAZAR DE TROYA > Head of Software Engineering > miguel.sala...@corintis.com <mailto:miguel.sala...@corintis.com> > Corintis SA > EPFL Innovation Park Building C > 1015 Lausanne > > <2024-08-1609_02_11-re_mailmigrationfromgoogletooffice365-sebastien.go...@corintis.com-co_4456a1bf-dd3e-46b7-85f9-21f278e66a79.png> > Here at Corintis we care for your privacy. That is why we have taken > appropriate measures to ensure that the data you have provided to us is > always secure.
