On Wed, 3 May 2017 at 09:29, Hoang Giang Bui <[email protected]> wrote:
> Dear Jed > > If I understood you correctly you suggest to avoid penalty by using the > Lagrange multiplier for the mortar constraint? In this case it leads to the > use of discrete Lagrange multiplier space. Do you or anyone already have > experience using discrete Lagrange multiplier space with Petsc? > Yes - this is similar to solving incompressible Stokes in which the pressure is a Lagrange multiplier enforcing the div(v)=0 constraint. Robust preconditioners for this problem are constructed using PCFIELDSPLIT. Thanks, Dave > There is also similar question on stackexchange > > https://scicomp.stackexchange.com/questions/25113/preconditioners-and-discrete-lagrange-multipliers > > Giang > > On Sat, Apr 29, 2017 at 3:34 PM, Jed Brown <[email protected]> wrote: > >> Hoang Giang Bui <[email protected]> writes: >> >> > Hi Barry >> > >> > The first block is from a standard solid mechanics discretization based >> on >> > balance of momentum equation. There is some material involved but in >> > principal it's well-posed elasticity equation with positive definite >> > tangent operator. The "gluing business" uses the mortar method to keep >> the >> > continuity of displacement. Instead of using Lagrange multiplier to >> treat >> > the constraint I used penalty method to penalize the energy. The >> > discretization form of mortar is quite simple >> > >> > \int_{\Gamma_1} { rho * (\delta u_1 - \delta u_2) * (u_1 - u_2) dA } >> > >> > rho is penalty parameter. In the simulation I initially set it low (~E) >> to >> > preserve the conditioning of the system. >> >> There are two things that can go wrong here with AMG: >> >> * The penalty term can mess up the strength of connection heuristics >> such that you get poor choice of C-points (classical AMG like >> BoomerAMG) or poor choice of aggregates (smoothed aggregation). >> >> * The penalty term can prevent Jacobi smoothing from being effective; in >> this case, it can lead to poor coarse basis functions (higher energy >> than they should be) and poor smoothing in an MG cycle. You can fix >> the poor smoothing in the MG cycle by using a stronger smoother, like >> ASM with some overlap. >> >> I'm generally not a fan of penalty methods due to the irritating >> tradeoffs and often poor solver performance. >> >> > In the figure below, the colorful blocks are u_1 and the base is u_2. >> Both >> > u_1 and u_2 use isoparametric quadratic approximation. >> > >> > >> > Snapshot.png >> > < >> https://drive.google.com/file/d/0Bw8Hmu0-YGQXc2hKQ1BhQ1I4OEU/view?usp=drive_web >> > >> > >> > >> > Giang >> > >> > On Fri, Apr 28, 2017 at 6:21 PM, Barry Smith <[email protected]> >> wrote: >> > >> >> >> >> Ok, so boomerAMG algebraic multigrid is not good for the first block. >> >> You mentioned the first block has two things glued together? AMG is >> >> fantastic for certain problems but doesn't work for everything. >> >> >> >> Tell us more about the first block, what PDE it comes from, what >> >> discretization, and what the "gluing business" is and maybe we'll have >> >> suggestions for how to precondition it. >> >> >> >> Barry >> >> >> >> > On Apr 28, 2017, at 3:56 AM, Hoang Giang Bui <[email protected]> >> wrote: >> >> > >> >> > It's in fact quite good >> >> > >> >> > Residual norms for fieldsplit_u_ solve. >> >> > 0 KSP Residual norm 4.014715925568e+00 >> >> > 1 KSP Residual norm 2.160497019264e-10 >> >> > Residual norms for fieldsplit_wp_ solve. >> >> > 0 KSP Residual norm 0.000000000000e+00 >> >> > 0 KSP preconditioned resid norm 4.014715925568e+00 true resid norm >> >> 9.006493082896e+06 ||r(i)||/||b|| 1.000000000000e+00 >> >> > Residual norms for fieldsplit_u_ solve. >> >> > 0 KSP Residual norm 9.999999999416e-01 >> >> > 1 KSP Residual norm 7.118380416383e-11 >> >> > Residual norms for fieldsplit_wp_ solve. >> >> > 0 KSP Residual norm 0.000000000000e+00 >> >> > 1 KSP preconditioned resid norm 1.701150951035e-10 true resid norm >> >> 5.494262251846e-04 ||r(i)||/||b|| 6.100334726599e-11 >> >> > Linear solve converged due to CONVERGED_ATOL iterations 1 >> >> > >> >> > Giang >> >> > >> >> > On Thu, Apr 27, 2017 at 5:25 PM, Barry Smith <[email protected]> >> wrote: >> >> > >> >> > Run again using LU on both blocks to see what happens. >> >> > >> >> > >> >> > > On Apr 27, 2017, at 2:14 AM, Hoang Giang Bui <[email protected]> >> >> wrote: >> >> > > >> >> > > I have changed the way to tie the nonconforming mesh. It seems the >> >> matrix now is better >> >> > > >> >> > > with -pc_type lu the output is >> >> > > 0 KSP preconditioned resid norm 3.308678584240e-01 true resid >> norm >> >> 9.006493082896e+06 ||r(i)||/||b|| 1.000000000000e+00 >> >> > > 1 KSP preconditioned resid norm 2.004313395301e-12 true resid >> norm >> >> 2.549872332830e-05 ||r(i)||/||b|| 2.831148938173e-12 >> >> > > Linear solve converged due to CONVERGED_ATOL iterations 1 >> >> > > >> >> > > >> >> > > with -pc_type fieldsplit -fieldsplit_u_pc_type hypre >> >> -fieldsplit_wp_pc_type lu the convergence is slow >> >> > > 0 KSP preconditioned resid norm 1.116302362553e-01 true resid >> norm >> >> 9.006493083520e+06 ||r(i)||/||b|| 1.000000000000e+00 >> >> > > 1 KSP preconditioned resid norm 2.582134825666e-02 true resid >> norm >> >> 9.268347719866e+06 ||r(i)||/||b|| 1.029073984060e+00 >> >> > > ... >> >> > > 824 KSP preconditioned resid norm 1.018542387738e-09 true resid >> norm >> >> 2.906608839310e+02 ||r(i)||/||b|| 3.227237074804e-05 >> >> > > 825 KSP preconditioned resid norm 9.743727947637e-10 true resid >> norm >> >> 2.820369993061e+02 ||r(i)||/||b|| 3.131485215062e-05 >> >> > > Linear solve converged due to CONVERGED_ATOL iterations 825 >> >> > > >> >> > > checking with additional -fieldsplit_u_ksp_type richardson >> >> -fieldsplit_u_ksp_monitor -fieldsplit_u_ksp_max_it 1 >> >> -fieldsplit_wp_ksp_type richardson -fieldsplit_wp_ksp_monitor >> >> -fieldsplit_wp_ksp_max_it 1 gives >> >> > > >> >> > > 0 KSP preconditioned resid norm 1.116302362553e-01 true resid >> norm >> >> 9.006493083520e+06 ||r(i)||/||b|| 1.000000000000e+00 >> >> > > Residual norms for fieldsplit_u_ solve. >> >> > > 0 KSP Residual norm 5.803507549280e-01 >> >> > > 1 KSP Residual norm 2.069538175950e-01 >> >> > > Residual norms for fieldsplit_wp_ solve. >> >> > > 0 KSP Residual norm 0.000000000000e+00 >> >> > > 1 KSP preconditioned resid norm 2.582134825666e-02 true resid >> norm >> >> 9.268347719866e+06 ||r(i)||/||b|| 1.029073984060e+00 >> >> > > Residual norms for fieldsplit_u_ solve. >> >> > > 0 KSP Residual norm 7.831796195225e-01 >> >> > > 1 KSP Residual norm 1.734608520110e-01 >> >> > > Residual norms for fieldsplit_wp_ solve. >> >> > > 0 KSP Residual norm 0.000000000000e+00 >> >> > > .... >> >> > > 823 KSP preconditioned resid norm 1.065070135605e-09 true resid >> norm >> >> 3.081881356833e+02 ||r(i)||/||b|| 3.421843916665e-05 >> >> > > Residual norms for fieldsplit_u_ solve. >> >> > > 0 KSP Residual norm 6.113806394327e-01 >> >> > > 1 KSP Residual norm 1.535465290944e-01 >> >> > > Residual norms for fieldsplit_wp_ solve. >> >> > > 0 KSP Residual norm 0.000000000000e+00 >> >> > > 824 KSP preconditioned resid norm 1.018542387746e-09 true resid >> norm >> >> 2.906608839353e+02 ||r(i)||/||b|| 3.227237074851e-05 >> >> > > Residual norms for fieldsplit_u_ solve. >> >> > > 0 KSP Residual norm 6.123437055586e-01 >> >> > > 1 KSP Residual norm 1.524661826133e-01 >> >> > > Residual norms for fieldsplit_wp_ solve. >> >> > > 0 KSP Residual norm 0.000000000000e+00 >> >> > > 825 KSP preconditioned resid norm 9.743727947718e-10 true resid >> norm >> >> 2.820369990571e+02 ||r(i)||/||b|| 3.131485212298e-05 >> >> > > Linear solve converged due to CONVERGED_ATOL iterations 825 >> >> > > >> >> > > >> >> > > The residual for wp block is zero since in this first step the rhs >> is >> >> zero. As can see in the output, the multigrid does not perform well to >> >> reduce the residual in the sub-solve. Is my observation right? what >> can be >> >> done to improve this? >> >> > > >> >> > > >> >> > > Giang >> >> > > >> >> > > On Tue, Apr 25, 2017 at 12:17 AM, Barry Smith <[email protected]> >> >> wrote: >> >> > > >> >> > > This can happen in the matrix is singular or nearly singular or >> if >> >> the factorization generates small pivots, which can occur for even >> >> nonsingular problems if the matrix is poorly scaled or just plain >> nasty. >> >> > > >> >> > > >> >> > > > On Apr 24, 2017, at 5:10 PM, Hoang Giang Bui <[email protected] >> > >> >> wrote: >> >> > > > >> >> > > > It took a while, here I send you the output >> >> > > > >> >> > > > 0 KSP preconditioned resid norm 3.129073545457e+05 true resid >> norm >> >> 9.015150492169e+06 ||r(i)||/||b|| 1.000000000000e+00 >> >> > > > 1 KSP preconditioned resid norm 7.442444222843e-01 true resid >> norm >> >> 1.003356247696e+02 ||r(i)||/||b|| 1.112966720375e-05 >> >> > > > 2 KSP preconditioned resid norm 3.267453132529e-07 true resid >> norm >> >> 3.216722968300e+01 ||r(i)||/||b|| 3.568130084011e-06 >> >> > > > 3 KSP preconditioned resid norm 1.155046883816e-11 true resid >> norm >> >> 3.234460376820e+01 ||r(i)||/||b|| 3.587805194854e-06 >> >> > > > Linear solve converged due to CONVERGED_ATOL iterations 3 >> >> > > > KSP Object: 4 MPI processes >> >> > > > type: gmres >> >> > > > GMRES: restart=1000, using Modified Gram-Schmidt >> >> Orthogonalization >> >> > > > GMRES: happy breakdown tolerance 1e-30 >> >> > > > maximum iterations=1000, initial guess is zero >> >> > > > tolerances: relative=1e-20, absolute=1e-09, divergence=10000 >> >> > > > left preconditioning >> >> > > > using PRECONDITIONED norm type for convergence test >> >> > > > PC Object: 4 MPI processes >> >> > > > type: lu >> >> > > > LU: out-of-place factorization >> >> > > > tolerance for zero pivot 2.22045e-14 >> >> > > > matrix ordering: natural >> >> > > > factor fill ratio given 0, needed 0 >> >> > > > Factored matrix follows: >> >> > > > Mat Object: 4 MPI processes >> >> > > > type: mpiaij >> >> > > > rows=973051, cols=973051 >> >> > > > package used to perform factorization: pastix >> >> > > > Error : 3.24786e-14 >> >> > > > total: nonzeros=0, allocated nonzeros=0 >> >> > > > total number of mallocs used during MatSetValues calls >> =0 >> >> > > > PaStiX run parameters: >> >> > > > Matrix type : Unsymmetric >> >> > > > Level of printing (0,1,2): 0 >> >> > > > Number of refinements iterations : 3 >> >> > > > Error : 3.24786e-14 >> >> > > > linear system matrix = precond matrix: >> >> > > > Mat Object: 4 MPI processes >> >> > > > type: mpiaij >> >> > > > rows=973051, cols=973051 >> >> > > > Error : 3.24786e-14 >> >> > > > total: nonzeros=9.90037e+07, allocated nonzeros=9.90037e+07 >> >> > > > total number of mallocs used during MatSetValues calls =0 >> >> > > > using I-node (on process 0) routines: found 78749 nodes, >> limit >> >> used is 5 >> >> > > > Error : 3.24786e-14 >> >> > > > >> >> > > > It doesn't do as you said. Something is not right here. I will >> look >> >> in depth. >> >> > > > >> >> > > > Giang >> >> > > > >> >> > > > On Mon, Apr 24, 2017 at 8:21 PM, Barry Smith <[email protected] >> > >> >> wrote: >> >> > > > >> >> > > > > On Apr 24, 2017, at 12:47 PM, Hoang Giang Bui < >> [email protected]> >> >> wrote: >> >> > > > > >> >> > > > > Good catch. I get this for the very first step, maybe at that >> time >> >> the rhs_w is zero. >> >> > > > >> >> > > > With the multiplicative composition the right hand side of >> the >> >> second solve is the initial right hand side of the second solve minus >> >> A_10*x where x is the solution to the first sub solve and A_10 is the >> lower >> >> left block of the outer matrix. So unless both the initial right hand >> side >> >> has a zero for the second block and A_10 is identically zero the right >> hand >> >> side for the second sub solve should not be zero. Is A_10 == 0? >> >> > > > >> >> > > > >> >> > > > > In the later step, it shows 2 step convergence >> >> > > > > >> >> > > > > Residual norms for fieldsplit_u_ solve. >> >> > > > > 0 KSP Residual norm 3.165886479830e+04 >> >> > > > > 1 KSP Residual norm 2.905922877684e-01 >> >> > > > > Residual norms for fieldsplit_wp_ solve. >> >> > > > > 0 KSP Residual norm 2.397669419027e-01 >> >> > > > > 1 KSP Residual norm 0.000000000000e+00 >> >> > > > > 0 KSP preconditioned resid norm 3.165886479920e+04 true resid >> >> norm 7.963616922323e+05 ||r(i)||/||b|| 1.000000000000e+00 >> >> > > > > Residual norms for fieldsplit_u_ solve. >> >> > > > > 0 KSP Residual norm 9.999891813771e-01 >> >> > > > > 1 KSP Residual norm 1.512000395579e-05 >> >> > > > > Residual norms for fieldsplit_wp_ solve. >> >> > > > > 0 KSP Residual norm 8.192702188243e-06 >> >> > > > > 1 KSP Residual norm 0.000000000000e+00 >> >> > > > > 1 KSP preconditioned resid norm 5.252183822848e-02 true resid >> >> norm 7.135927677844e+04 ||r(i)||/||b|| 8.960661653427e-02 >> >> > > > >> >> > > > The outer residual norms are still wonky, the preconditioned >> >> residual norm goes from 3.165886479920e+04 to 5.252183822848e-02 which >> is a >> >> huge drop but the 7.963616922323e+05 drops very much less >> >> 7.135927677844e+04. This is not normal. >> >> > > > >> >> > > > What if you just use -pc_type lu for the entire system (no >> >> fieldsplit), does the true residual drop to almost zero in the first >> >> iteration (as it should?). Send the output. >> >> > > > >> >> > > > >> >> > > > >> >> > > > > Residual norms for fieldsplit_u_ solve. >> >> > > > > 0 KSP Residual norm 6.946213936597e-01 >> >> > > > > 1 KSP Residual norm 1.195514007343e-05 >> >> > > > > Residual norms for fieldsplit_wp_ solve. >> >> > > > > 0 KSP Residual norm 1.025694497535e+00 >> >> > > > > 1 KSP Residual norm 0.000000000000e+00 >> >> > > > > 2 KSP preconditioned resid norm 8.785709535405e-03 true resid >> >> norm 1.419341799277e+04 ||r(i)||/||b|| 1.782282866091e-02 >> >> > > > > Residual norms for fieldsplit_u_ solve. >> >> > > > > 0 KSP Residual norm 7.255149996405e-01 >> >> > > > > 1 KSP Residual norm 6.583512434218e-06 >> >> > > > > Residual norms for fieldsplit_wp_ solve. >> >> > > > > 0 KSP Residual norm 1.015229700337e+00 >> >> > > > > 1 KSP Residual norm 0.000000000000e+00 >> >> > > > > 3 KSP preconditioned resid norm 7.110407712709e-04 true resid >> >> norm 5.284940654154e+02 ||r(i)||/||b|| 6.636357205153e-04 >> >> > > > > Residual norms for fieldsplit_u_ solve. >> >> > > > > 0 KSP Residual norm 3.512243341400e-01 >> >> > > > > 1 KSP Residual norm 2.032490351200e-06 >> >> > > > > Residual norms for fieldsplit_wp_ solve. >> >> > > > > 0 KSP Residual norm 1.282327290982e+00 >> >> > > > > 1 KSP Residual norm 0.000000000000e+00 >> >> > > > > 4 KSP preconditioned resid norm 3.482036620521e-05 true resid >> >> norm 4.291231924307e+01 ||r(i)||/||b|| 5.388546393133e-05 >> >> > > > > Residual norms for fieldsplit_u_ solve. >> >> > > > > 0 KSP Residual norm 3.423609338053e-01 >> >> > > > > 1 KSP Residual norm 4.213703301972e-07 >> >> > > > > Residual norms for fieldsplit_wp_ solve. >> >> > > > > 0 KSP Residual norm 1.157384757538e+00 >> >> > > > > 1 KSP Residual norm 0.000000000000e+00 >> >> > > > > 5 KSP preconditioned resid norm 1.203470314534e-06 true resid >> >> norm 4.544956156267e+00 ||r(i)||/||b|| 5.707150658550e-06 >> >> > > > > Residual norms for fieldsplit_u_ solve. >> >> > > > > 0 KSP Residual norm 3.838596289995e-01 >> >> > > > > 1 KSP Residual norm 9.927864176103e-08 >> >> > > > > Residual norms for fieldsplit_wp_ solve. >> >> > > > > 0 KSP Residual norm 1.066298905618e+00 >> >> > > > > 1 KSP Residual norm 0.000000000000e+00 >> >> > > > > 6 KSP preconditioned resid norm 3.331619244266e-08 true resid >> >> norm 2.821511729024e+00 ||r(i)||/||b|| 3.543002829675e-06 >> >> > > > > Residual norms for fieldsplit_u_ solve. >> >> > > > > 0 KSP Residual norm 4.624964188094e-01 >> >> > > > > 1 KSP Residual norm 6.418229775372e-08 >> >> > > > > Residual norms for fieldsplit_wp_ solve. >> >> > > > > 0 KSP Residual norm 9.800784311614e-01 >> >> > > > > 1 KSP Residual norm 0.000000000000e+00 >> >> > > > > 7 KSP preconditioned resid norm 8.788046233297e-10 true resid >> >> norm 2.849209671705e+00 ||r(i)||/||b|| 3.577783436215e-06 >> >> > > > > Linear solve converged due to CONVERGED_ATOL iterations 7 >> >> > > > > >> >> > > > > The outer operator is an explicit matrix. >> >> > > > > >> >> > > > > Giang >> >> > > > > >> >> > > > > On Mon, Apr 24, 2017 at 7:32 PM, Barry Smith < >> [email protected]> >> >> wrote: >> >> > > > > >> >> > > > > > On Apr 24, 2017, at 3:16 AM, Hoang Giang Bui < >> [email protected]> >> >> wrote: >> >> > > > > > >> >> > > > > > Thanks Barry, trying with -fieldsplit_u_type lu gives better >> >> convergence. I still used 4 procs though, probably with 1 proc it >> should >> >> also be the same. >> >> > > > > > >> >> > > > > > The u block used a Nitsche-type operator to connect two >> >> non-matching domains. I don't think it will leave some rigid body >> motion >> >> leads to not sufficient constraints. Maybe you have other idea? >> >> > > > > > >> >> > > > > > Residual norms for fieldsplit_u_ solve. >> >> > > > > > 0 KSP Residual norm 3.129067184300e+05 >> >> > > > > > 1 KSP Residual norm 5.906261468196e-01 >> >> > > > > > Residual norms for fieldsplit_wp_ solve. >> >> > > > > > 0 KSP Residual norm 0.000000000000e+00 >> >> > > > > >> >> > > > > ^^^^ something is wrong here. The sub solve should not be >> >> starting with a 0 residual (this means the right hand side for this sub >> >> solve is zero which it should not be). >> >> > > > > >> >> > > > > > FieldSplit with MULTIPLICATIVE composition: total splits = 2 >> >> > > > > >> >> > > > > >> >> > > > > How are you providing the outer operator? As an explicit >> matrix >> >> or with some shell matrix? >> >> > > > > >> >> > > > > >> >> > > > > >> >> > > > > > 0 KSP preconditioned resid norm 3.129067184300e+05 true >> resid >> >> norm 9.015150492169e+06 ||r(i)||/||b|| 1.000000000000e+00 >> >> > > > > > Residual norms for fieldsplit_u_ solve. >> >> > > > > > 0 KSP Residual norm 9.999955993437e-01 >> >> > > > > > 1 KSP Residual norm 4.019774691831e-06 >> >> > > > > > Residual norms for fieldsplit_wp_ solve. >> >> > > > > > 0 KSP Residual norm 0.000000000000e+00 >> >> > > > > > 1 KSP preconditioned resid norm 5.003913641475e-01 true >> resid >> >> norm 4.692996324114e+01 ||r(i)||/||b|| 5.205677185522e-06 >> >> > > > > > Residual norms for fieldsplit_u_ solve. >> >> > > > > > 0 KSP Residual norm 1.000012180204e+00 >> >> > > > > > 1 KSP Residual norm 1.017367950422e-05 >> >> > > > > > Residual norms for fieldsplit_wp_ solve. >> >> > > > > > 0 KSP Residual norm 0.000000000000e+00 >> >> > > > > > 2 KSP preconditioned resid norm 2.330910333756e-07 true >> resid >> >> norm 3.474855463983e+01 ||r(i)||/||b|| 3.854461960453e-06 >> >> > > > > > Residual norms for fieldsplit_u_ solve. >> >> > > > > > 0 KSP Residual norm 1.000004200085e+00 >> >> > > > > > 1 KSP Residual norm 6.231613102458e-06 >> >> > > > > > Residual norms for fieldsplit_wp_ solve. >> >> > > > > > 0 KSP Residual norm 0.000000000000e+00 >> >> > > > > > 3 KSP preconditioned resid norm 8.671259838389e-11 true >> resid >> >> norm 3.545103468011e+01 ||r(i)||/||b|| 3.932384125024e-06 >> >> > > > > > Linear solve converged due to CONVERGED_ATOL iterations 3 >> >> > > > > > KSP Object: 4 MPI processes >> >> > > > > > type: gmres >> >> > > > > > GMRES: restart=1000, using Modified Gram-Schmidt >> >> Orthogonalization >> >> > > > > > GMRES: happy breakdown tolerance 1e-30 >> >> > > > > > maximum iterations=1000, initial guess is zero >> >> > > > > > tolerances: relative=1e-20, absolute=1e-09, >> divergence=10000 >> >> > > > > > left preconditioning >> >> > > > > > using PRECONDITIONED norm type for convergence test >> >> > > > > > PC Object: 4 MPI processes >> >> > > > > > type: fieldsplit >> >> > > > > > FieldSplit with MULTIPLICATIVE composition: total splits >> = 2 >> >> > > > > > Solver info for each split is in the following KSP >> objects: >> >> > > > > > Split number 0 Defined by IS >> >> > > > > > KSP Object: (fieldsplit_u_) 4 MPI processes >> >> > > > > > type: richardson >> >> > > > > > Richardson: damping factor=1 >> >> > > > > > maximum iterations=1, initial guess is zero >> >> > > > > > tolerances: relative=1e-05, absolute=1e-50, >> >> divergence=10000 >> >> > > > > > left preconditioning >> >> > > > > > using PRECONDITIONED norm type for convergence test >> >> > > > > > PC Object: (fieldsplit_u_) 4 MPI processes >> >> > > > > > type: lu >> >> > > > > > LU: out-of-place factorization >> >> > > > > > tolerance for zero pivot 2.22045e-14 >> >> > > > > > matrix ordering: natural >> >> > > > > > factor fill ratio given 0, needed 0 >> >> > > > > > Factored matrix follows: >> >> > > > > > Mat Object: 4 MPI processes >> >> > > > > > type: mpiaij >> >> > > > > > rows=938910, cols=938910 >> >> > > > > > package used to perform factorization: pastix >> >> > > > > > total: nonzeros=0, allocated nonzeros=0 >> >> > > > > > Error : 3.36878e-14 >> >> > > > > > total number of mallocs used during MatSetValues >> calls >> >> =0 >> >> > > > > > PaStiX run parameters: >> >> > > > > > Matrix type : >> Unsymmetric >> >> > > > > > Level of printing (0,1,2): 0 >> >> > > > > > Number of refinements iterations : 3 >> >> > > > > > Error : 3.36878e-14 >> >> > > > > > linear system matrix = precond matrix: >> >> > > > > > Mat Object: (fieldsplit_u_) 4 MPI processes >> >> > > > > > type: mpiaij >> >> > > > > > rows=938910, cols=938910, bs=3 >> >> > > > > > Error : 3.36878e-14 >> >> > > > > > Error : 3.36878e-14 >> >> > > > > > total: nonzeros=8.60906e+07, allocated >> >> nonzeros=8.60906e+07 >> >> > > > > > total number of mallocs used during MatSetValues >> calls =0 >> >> > > > > > using I-node (on process 0) routines: found 78749 >> >> nodes, limit used is 5 >> >> > > > > > Split number 1 Defined by IS >> >> > > > > > KSP Object: (fieldsplit_wp_) 4 MPI processes >> >> > > > > > type: richardson >> >> > > > > > Richardson: damping factor=1 >> >> > > > > > maximum iterations=1, initial guess is zero >> >> > > > > > tolerances: relative=1e-05, absolute=1e-50, >> >> divergence=10000 >> >> > > > > > left preconditioning >> >> > > > > > using PRECONDITIONED norm type for convergence test >> >> > > > > > PC Object: (fieldsplit_wp_) 4 MPI processes >> >> > > > > > type: lu >> >> > > > > > LU: out-of-place factorization >> >> > > > > > tolerance for zero pivot 2.22045e-14 >> >> > > > > > matrix ordering: natural >> >> > > > > > factor fill ratio given 0, needed 0 >> >> > > > > > Factored matrix follows: >> >> > > > > > Mat Object: 4 MPI processes >> >> > > > > > type: mpiaij >> >> > > > > > rows=34141, cols=34141 >> >> > > > > > package used to perform factorization: pastix >> >> > > > > > Error : -nan >> >> > > > > > Error : -nan >> >> > > > > > Error : -nan >> >> > > > > > total: nonzeros=0, allocated nonzeros=0 >> >> > > > > > total number of mallocs used during >> MatSetValues >> >> calls =0 >> >> > > > > > PaStiX run parameters: >> >> > > > > > Matrix type : >> Symmetric >> >> > > > > > Level of printing (0,1,2): 0 >> >> > > > > > Number of refinements iterations : 0 >> >> > > > > > Error : -nan >> >> > > > > > linear system matrix = precond matrix: >> >> > > > > > Mat Object: (fieldsplit_wp_) 4 MPI processes >> >> > > > > > type: mpiaij >> >> > > > > > rows=34141, cols=34141 >> >> > > > > > total: nonzeros=485655, allocated nonzeros=485655 >> >> > > > > > total number of mallocs used during MatSetValues >> calls =0 >> >> > > > > > not using I-node (on process 0) routines >> >> > > > > > linear system matrix = precond matrix: >> >> > > > > > Mat Object: 4 MPI processes >> >> > > > > > type: mpiaij >> >> > > > > > rows=973051, cols=973051 >> >> > > > > > total: nonzeros=9.90037e+07, allocated >> nonzeros=9.90037e+07 >> >> > > > > > total number of mallocs used during MatSetValues calls =0 >> >> > > > > > using I-node (on process 0) routines: found 78749 >> nodes, >> >> limit used is 5 >> >> > > > > > >> >> > > > > > >> >> > > > > > >> >> > > > > > Giang >> >> > > > > > >> >> > > > > > On Sun, Apr 23, 2017 at 10:19 PM, Barry Smith < >> >> [email protected]> wrote: >> >> > > > > > >> >> > > > > > > On Apr 23, 2017, at 2:42 PM, Hoang Giang Bui < >> >> [email protected]> wrote: >> >> > > > > > > >> >> > > > > > > Dear Matt/Barry >> >> > > > > > > >> >> > > > > > > With your options, it results in >> >> > > > > > > >> >> > > > > > > 0 KSP preconditioned resid norm 1.106709687386e+31 true >> >> resid norm 9.015150491938e+06 ||r(i)||/||b|| 1.000000000000e+00 >> >> > > > > > > Residual norms for fieldsplit_u_ solve. >> >> > > > > > > 0 KSP Residual norm 2.407308987203e+36 >> >> > > > > > > 1 KSP Residual norm 5.797185652683e+72 >> >> > > > > > >> >> > > > > > It looks like Matt is right, hypre is seemly producing >> useless >> >> garbage. >> >> > > > > > >> >> > > > > > First how do things run on one process. If you have similar >> >> problems then debug on one process (debugging any kind of problem is >> always >> >> far easy on one process). >> >> > > > > > >> >> > > > > > First run with -fieldsplit_u_type lu (instead of using >> hypre) to >> >> see if that works or also produces something bad. >> >> > > > > > >> >> > > > > > What is the operator and the boundary conditions for u? It >> could >> >> be singular. >> >> > > > > > >> >> > > > > > >> >> > > > > > >> >> > > > > > >> >> > > > > > >> >> > > > > > >> >> > > > > > > Residual norms for fieldsplit_wp_ solve. >> >> > > > > > > 0 KSP Residual norm 0.000000000000e+00 >> >> > > > > > > ... >> >> > > > > > > 999 KSP preconditioned resid norm 2.920157329174e+12 true >> >> resid norm 9.015683504616e+06 ||r(i)||/||b|| 1.000059124102e+00 >> >> > > > > > > Residual norms for fieldsplit_u_ solve. >> >> > > > > > > 0 KSP Residual norm 1.533726746719e+36 >> >> > > > > > > 1 KSP Residual norm 3.692757392261e+72 >> >> > > > > > > Residual norms for fieldsplit_wp_ solve. >> >> > > > > > > 0 KSP Residual norm 0.000000000000e+00 >> >> > > > > > > >> >> > > > > > > Do you suggest that the pastix solver for the "wp" block >> >> encounters small pivot? In addition, seem like the "u" block is also >> >> singular. >> >> > > > > > > >> >> > > > > > > Giang >> >> > > > > > > >> >> > > > > > > On Sun, Apr 23, 2017 at 7:39 PM, Barry Smith < >> >> [email protected]> wrote: >> >> > > > > > > >> >> > > > > > > Huge preconditioned norms but normal unpreconditioned >> norms >> >> almost always come from a very small pivot in an LU or ILU >> factorization. >> >> > > > > > > >> >> > > > > > > The first thing to do is monitor the two sub solves. Run >> >> with the additional options -fieldsplit_u_ksp_type richardson >> >> -fieldsplit_u_ksp_monitor -fieldsplit_u_ksp_max_it 1 >> >> -fieldsplit_wp_ksp_type richardson -fieldsplit_wp_ksp_monitor >> >> -fieldsplit_wp_ksp_max_it 1 >> >> > > > > > > >> >> > > > > > > > On Apr 23, 2017, at 12:22 PM, Hoang Giang Bui < >> >> [email protected]> wrote: >> >> > > > > > > > >> >> > > > > > > > Hello >> >> > > > > > > > >> >> > > > > > > > I encountered a strange convergence behavior that I have >> >> trouble to understand >> >> > > > > > > > >> >> > > > > > > > KSPSetFromOptions completed >> >> > > > > > > > 0 KSP preconditioned resid norm 1.106709687386e+31 true >> >> resid norm 9.015150491938e+06 ||r(i)||/||b|| 1.000000000000e+00 >> >> > > > > > > > 1 KSP preconditioned resid norm 2.933141742664e+29 true >> >> resid norm 9.015152282123e+06 ||r(i)||/||b|| 1.000000198575e+00 >> >> > > > > > > > 2 KSP preconditioned resid norm 9.686409637174e+16 true >> >> resid norm 9.015354521944e+06 ||r(i)||/||b|| 1.000022631902e+00 >> >> > > > > > > > 3 KSP preconditioned resid norm 4.219243615809e+15 true >> >> resid norm 9.017157702420e+06 ||r(i)||/||b|| 1.000222648583e+00 >> >> > > > > > > > ..... >> >> > > > > > > > 999 KSP preconditioned resid norm 3.043754298076e+12 true >> >> resid norm 9.015425041089e+06 ||r(i)||/||b|| 1.000030454195e+00 >> >> > > > > > > > 1000 KSP preconditioned resid norm 3.043000287819e+12 >> true >> >> resid norm 9.015424313455e+06 ||r(i)||/||b|| 1.000030373483e+00 >> >> > > > > > > > Linear solve did not converge due to DIVERGED_ITS >> iterations >> >> 1000 >> >> > > > > > > > KSP Object: 4 MPI processes >> >> > > > > > > > type: gmres >> >> > > > > > > > GMRES: restart=1000, using Modified Gram-Schmidt >> >> Orthogonalization >> >> > > > > > > > GMRES: happy breakdown tolerance 1e-30 >> >> > > > > > > > maximum iterations=1000, initial guess is zero >> >> > > > > > > > tolerances: relative=1e-20, absolute=1e-09, >> >> divergence=10000 >> >> > > > > > > > left preconditioning >> >> > > > > > > > using PRECONDITIONED norm type for convergence test >> >> > > > > > > > PC Object: 4 MPI processes >> >> > > > > > > > type: fieldsplit >> >> > > > > > > > FieldSplit with MULTIPLICATIVE composition: total >> splits >> >> = 2 >> >> > > > > > > > Solver info for each split is in the following KSP >> >> objects: >> >> > > > > > > > Split number 0 Defined by IS >> >> > > > > > > > KSP Object: (fieldsplit_u_) 4 MPI processes >> >> > > > > > > > type: preonly >> >> > > > > > > > maximum iterations=10000, initial guess is zero >> >> > > > > > > > tolerances: relative=1e-05, absolute=1e-50, >> >> divergence=10000 >> >> > > > > > > > left preconditioning >> >> > > > > > > > using NONE norm type for convergence test >> >> > > > > > > > PC Object: (fieldsplit_u_) 4 MPI processes >> >> > > > > > > > type: hypre >> >> > > > > > > > HYPRE BoomerAMG preconditioning >> >> > > > > > > > HYPRE BoomerAMG: Cycle type V >> >> > > > > > > > HYPRE BoomerAMG: Maximum number of levels 25 >> >> > > > > > > > HYPRE BoomerAMG: Maximum number of iterations PER >> >> hypre call 1 >> >> > > > > > > > HYPRE BoomerAMG: Convergence tolerance PER hypre >> >> call 0 >> >> > > > > > > > HYPRE BoomerAMG: Threshold for strong coupling >> 0.6 >> >> > > > > > > > HYPRE BoomerAMG: Interpolation truncation factor >> 0 >> >> > > > > > > > HYPRE BoomerAMG: Interpolation: max elements per >> row >> >> 0 >> >> > > > > > > > HYPRE BoomerAMG: Number of levels of aggressive >> >> coarsening 0 >> >> > > > > > > > HYPRE BoomerAMG: Number of paths for aggressive >> >> coarsening 1 >> >> > > > > > > > HYPRE BoomerAMG: Maximum row sums 0.9 >> >> > > > > > > > HYPRE BoomerAMG: Sweeps down 1 >> >> > > > > > > > HYPRE BoomerAMG: Sweeps up 1 >> >> > > > > > > > HYPRE BoomerAMG: Sweeps on coarse 1 >> >> > > > > > > > HYPRE BoomerAMG: Relax down >> >> symmetric-SOR/Jacobi >> >> > > > > > > > HYPRE BoomerAMG: Relax up >> >> symmetric-SOR/Jacobi >> >> > > > > > > > HYPRE BoomerAMG: Relax on coarse >> >> Gaussian-elimination >> >> > > > > > > > HYPRE BoomerAMG: Relax weight (all) 1 >> >> > > > > > > > HYPRE BoomerAMG: Outer relax weight (all) 1 >> >> > > > > > > > HYPRE BoomerAMG: Using CF-relaxation >> >> > > > > > > > HYPRE BoomerAMG: Measure type local >> >> > > > > > > > HYPRE BoomerAMG: Coarsen type PMIS >> >> > > > > > > > HYPRE BoomerAMG: Interpolation type classical >> >> > > > > > > > linear system matrix = precond matrix: >> >> > > > > > > > Mat Object: (fieldsplit_u_) 4 MPI >> processes >> >> > > > > > > > type: mpiaij >> >> > > > > > > > rows=938910, cols=938910, bs=3 >> >> > > > > > > > total: nonzeros=8.60906e+07, allocated >> >> nonzeros=8.60906e+07 >> >> > > > > > > > total number of mallocs used during MatSetValues >> >> calls =0 >> >> > > > > > > > using I-node (on process 0) routines: found >> 78749 >> >> nodes, limit used is 5 >> >> > > > > > > > Split number 1 Defined by IS >> >> > > > > > > > KSP Object: (fieldsplit_wp_) 4 MPI processes >> >> > > > > > > > type: preonly >> >> > > > > > > > maximum iterations=10000, initial guess is zero >> >> > > > > > > > tolerances: relative=1e-05, absolute=1e-50, >> >> divergence=10000 >> >> > > > > > > > left preconditioning >> >> > > > > > > > using NONE norm type for convergence test >> >> > > > > > > > PC Object: (fieldsplit_wp_) 4 MPI processes >> >> > > > > > > > type: lu >> >> > > > > > > > LU: out-of-place factorization >> >> > > > > > > > tolerance for zero pivot 2.22045e-14 >> >> > > > > > > > matrix ordering: natural >> >> > > > > > > > factor fill ratio given 0, needed 0 >> >> > > > > > > > Factored matrix follows: >> >> > > > > > > > Mat Object: 4 MPI processes >> >> > > > > > > > type: mpiaij >> >> > > > > > > > rows=34141, cols=34141 >> >> > > > > > > > package used to perform factorization: >> pastix >> >> > > > > > > > Error : -nan >> >> > > > > > > > Error : -nan >> >> > > > > > > > total: nonzeros=0, allocated nonzeros=0 >> >> > > > > > > > Error : -nan >> >> > > > > > > > total number of mallocs used during MatSetValues >> calls =0 >> >> > > > > > > > PaStiX run parameters: >> >> > > > > > > > Matrix type : >> >> Symmetric >> >> > > > > > > > Level of printing (0,1,2): 0 >> >> > > > > > > > Number of refinements iterations : 0 >> >> > > > > > > > Error : -nan >> >> > > > > > > > linear system matrix = precond matrix: >> >> > > > > > > > Mat Object: (fieldsplit_wp_) 4 MPI >> processes >> >> > > > > > > > type: mpiaij >> >> > > > > > > > rows=34141, cols=34141 >> >> > > > > > > > total: nonzeros=485655, allocated nonzeros=485655 >> >> > > > > > > > total number of mallocs used during MatSetValues >> >> calls =0 >> >> > > > > > > > not using I-node (on process 0) routines >> >> > > > > > > > linear system matrix = precond matrix: >> >> > > > > > > > Mat Object: 4 MPI processes >> >> > > > > > > > type: mpiaij >> >> > > > > > > > rows=973051, cols=973051 >> >> > > > > > > > total: nonzeros=9.90037e+07, allocated >> >> nonzeros=9.90037e+07 >> >> > > > > > > > total number of mallocs used during MatSetValues >> calls =0 >> >> > > > > > > > using I-node (on process 0) routines: found 78749 >> >> nodes, limit used is 5 >> >> > > > > > > > >> >> > > > > > > > The pattern of convergence gives a hint that this system >> is >> >> somehow bad/singular. But I don't know why the preconditioned error >> goes up >> >> too high. Anyone has an idea? >> >> > > > > > > > >> >> > > > > > > > Best regards >> >> > > > > > > > Giang Bui >> >> > > > > > > > >> >> > > > > > > >> >> > > > > > > >> >> > > > > > >> >> > > > > > >> >> > > > > >> >> > > > > >> >> > > > >> >> > > > >> >> > > >> >> > > >> >> > >> >> > >> >> >> >> >> > >
