Suggestions wanted for solution to "MLMG failed" 2nd #4675

APTX-4869-core · 2025-09-25T13:47:59Z

APTX-4869-core
Sep 25, 2025

Hello AMReX Team!

I encountered another MLMG failed problem during my simulation which is the residual blowing up after 6200 steps.

And before MLMG failed, it ran 6200 steps smoothly, so it seemed to be a sudden crash of the solver.

How can I adjust my settings to avoid this problem? Any advice is appreciable, thanks in advance sincerely!

Since I can run such many steps, I think the problem may not be serious and does not involve code problems or boundary conditions.

And my settings for the simulation is following:

amr.n_cell                      =  256 256  # Grid cells at coarsest AMRlevel
amr.max_level                   =  0           # Max AMR level in hierarchy

nodal_proj.proj_tol                = 1.e-10
nodal_proj.proj_abs_tol            = 1.e-10
#nodal_proj.max_fmg_iter = 0
nodal_proj.mg_max_coarsening_level = 0  # Default = 20 if multigrid is used
nodal_proj.bottom_solver           = hypre
nodal_proj.bottom_verbose          = 1
#nodal_proj.agglomeration = 1    # Do agglomeration on AMR Level 0?
#nodal_proj.consolidation = 1    # Do consolidation?

mac_proj.bottom_solver             = hypre
mac_proj.bottom_verbose            = 1 
#mac_proj.mg_max_coarsening_level   = 0  # No. of GMG coarsening level before calling hypre
mac_proj.mac_tol                   = 1.e-10
mac_proj.mac_abs_tol               = 1.e-10
#mac_proj.max_fmg_iter = 1     # of F-cycles before switching to V.  To do pure V-cycle, set to 0
#mac_proj.agglomeration = 1    # Do agglomeration on AMR Level 0?
#mac_proj.consolidation = 1    # Do consolidation?

hypre.hypre_solver                 = BoomerAMG
hypre.bamg_verbose                 = 1
#hypre.hypre_preconditioner = BoomerAMG  # BoomerAMG can't use preconditioned
#hypre.adjust_singular_matrix = true
#hypre.bamg_max_levels = 20  # Default = 20 in AMReX, but default = 25 in Hypre.
#hypre.bamg_strong_threshold = 0.25 in 2D, 0.57 in 3D, in elasticity problem = 0.9
hypre.bamg_coarsen_type            = 6  # Default = 6 in AMReX, default = 10 in Hypre
hypre.bamg_cycle_type              = 1  # Default = 1
hypre.bamg_relax_type              = 6  # Default = 6
hypre.bamg_relax_order              = 1  # Default = 1, default = 0 in Hypre
hypre.bamg_interp_type              = 6  # Default = 0 in AMReX, default = 6 in Hypre

And the log is following:

Advancing grids at level 0 : starting time = 3.116417353 with dt = 0.0005
Cells num in 0 th level = 65536
Total cells num = 65536
NavierStokes::advance(): before velocity update:
max(abs(u/v))  = 0.01638292415  0.01301560138
max(abs(gpx/gpy/p)) = 73.1065296  88.57824711  0.5278943266
... predict edge velocities
... mac_projection
... mac_project at level 0
MLMG: Initial rhs               = 0.5967878719
MLMG: Initial residual (resid0) = 0.5967878719
MLMG: Final Iter. 9 resid, resid/bnorm = 5.180811335e-11, 8.681160559e-11
MLMG: Timers: Solve = 0.005362014 Iter = 0.005167489 Bottom = 0.0003311190001
SUM of DIV(U_edge) = -7.22219223087503e-15
NavierStokesBase:mac_project(): lev: 0, time: 0.005930962
... advect velocities
... advect scalars
... update scalars
reinit level-set func...
... update velocities 
... Diffusion::diffuse_velocity() lev: 0
MLMG: Initial rhs               = 12.82855807
MLMG: Initial residual (resid0) = 0.001222950721
MLMG: Final Iter. 3 resid, resid/bnorm = 1.609387623e-10, 1.254535088e-11
MLMG: Timers: Solve = 0.002548343 Iter = 0.002184033 Bottom = 2.506999999e-05
Diffusion::diffuse_velocity(): lev: 0, time: 0.002990486
NavierStokes:velocity_diffusion_update(): lev: 0, time: 0.003015697
compute_surface_tension...
heavi derive's norm = 127.9836201
tension's norm = 73.38251608
NavierStokes::advance(): before nodal projection 
max(abs(u/v))  = 0.01638239079  0.01301611786
max(abs(gpx/gpy/p)) = 73.1065296  88.57824711  0.5278943266
... Projection::level_project() at level 0
Nodal Projection:
 >> Before projection:
  * On lev 0 max(abs(rhs)) = 558.4852429

MLMG: Initial rhs               = 558.4852429
MLMG: Initial residual (resid0) = 558.4852429
MLMG: Final Iter. 3 resid, resid/bnorm = 4.024514055e-11, 7.206124255e-14
MLMG: Timers: Solve = 0.068301952 Iter = 0.06821853 Bottom = 0.068024045
 >> After projection:
  * On lev 0 max(abs(rhs)) = 166.3876701

Projection::level_project(): lev: 0, time: 0.068546319
NavierStokes::advance(): exiting.
max(abs(u/v))  = 0.01638236868  0.01301609567
max(abs(gpx/gpy/p)) = 73.09805955  88.60526426  0.5279254238
Advancing grids at level 0 : starting time = 3.116917353 with dt = 0.0005
Cells num in 0 th level = 65536
Total cells num = 65536
NavierStokes::advance(): before velocity update:
max(abs(u/v))  = 0.01638236868  0.01301609567
max(abs(gpx/gpy/p)) = 73.09805955  88.60526426  0.5279254238
... predict edge velocities
... mac_projection
... mac_project at level 0
MLMG: Initial rhs               = 0.5973230279
MLMG: Initial residual (resid0) = 0.5973230279
MLMG: Final Iter. 9 resid, resid/bnorm = 5.17526022e-11, 8.664089578e-11
MLMG: Timers: Solve = 0.005336564 Iter = 0.005139429 Bottom = 0.000328149
SUM of DIV(U_edge) = -1.3780836310379e-14
NavierStokesBase:mac_project(): lev: 0, time: 0.005842508
... advect velocities
... advect scalars
... update scalars
reinit level-set func...
... update velocities 
... Diffusion::diffuse_velocity() lev: 0
MLMG: Initial rhs               = 12.8302711
MLMG: Initial residual (resid0) = 0.001222641547
MLMG: Final Iter. 3 resid, resid/bnorm = 1.617680781e-10, 1.260831333e-11
MLMG: Timers: Solve = 0.002494662 Iter = 0.002149552 Bottom = 2.509999996e-05
Diffusion::diffuse_velocity(): lev: 0, time: 0.002963116
NavierStokes:velocity_diffusion_update(): lev: 0, time: 0.002986826
compute_surface_tension...
heavi derive's norm = 127.9848434
tension's norm = 73.40817604
NavierStokes::advance(): before nodal projection 
max(abs(u/v))  = 0.01638179441  0.01301660943
max(abs(gpx/gpy/p)) = 73.09805955  88.60526426  0.5279254238
... Projection::level_project() at level 0
Nodal Projection:
 >> Before projection:
  * On lev 0 max(abs(rhs)) = 557.736831

MLMG: Initial rhs               = 557.736831
MLMG: Initial residual (resid0) = 557.736831
MLMG: Failing to converge after 3 iterations. resid, resid/bnorm = 3.226109411e+31, 5.784286122e+28

zingale · 2025-09-26T13:00:39Z

zingale
Sep 26, 2025
Collaborator

doesn't this means that you are not doing multigrid at all?

nodal_proj.mg_max_coarsening_level = 0  # Default = 20 if multigrid is used

but instead just setting up the linear system and passing it to hypre?

3 replies

WeiqunZhang Sep 26, 2025
Maintainer

I believe @zingale is right. It uses hypre. So you might try to tweak the hypre parameters.

APTX-4869-core Sep 28, 2025
Author

Thanks for the advice of @zingale and @WeiqunZhang!
I turned off the hypre in the params to give it all to the MLMG, but it failed after 1200 steps, and the tolerance is set to 1e-12.
If I set it to 1e-10, it would fail after 900 steps...
Should I enlarge the iteration steps more than 100?
And the params and log are following:

amr.n_cell`                      =  256 256  # Grid cells at coarsest AMRlevel
amr.max_level                   =  0           # Max AMR level in hierarchy

nodal_proj.proj_tol                = 1.e-12
nodal_proj.proj_abs_tol            = 1.e-12
#nodal_proj.max_fmg_iter = 0
nodal_proj.mg_max_coarsening_level = 20 
nodal_proj.bottom_verbose          = 1
#nodal_proj.agglomeration = 1    # Do agglomeration on AMR Level 0?
#nodal_proj.consolidation = 1    # Do consolidation?

mac_proj.bottom_verbose            = 1 
#mac_proj.mg_max_coarsening_level   = 0  # No. of GMG coarsening level before calling hypre
mac_proj.mac_tol                   = 1.e-12
mac_proj.mac_abs_tol               = 1.e-12
#mac_proj.max_fmg_iter = 1     # of F-cycles before switching to V.  To do pure V-cycle, set to 0
#mac_proj.agglomeration = 1    # Do agglomeration on AMR Level 0?
#mac_proj.consolidation = 1    # Do consolidation?

NavierStokes::advance(): before nodal projection 
max(abs(u/v))  = 0.02057512795  0.02410152857
max(abs(gpx/gpy/p)) = 245.9147371  161.5098177  1.519241919
... Projection::level_project() at level 0
Nodal Projection:
Before projection:
On lev 0 max(abs(rhs)) = 1054.991952

MLMG: Initial rhs               = 1054.991952
MLMG: Initial residual (resid0) = 1054.991952
MLCGSolver_BiCGStab: Initial error (error0) =        0.0001903207432
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 4.228027309e-17
MLCGSolver_BiCGStab: Initial error (error0) =        1.972563596e-05
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 4.0256922e-17
MLCGSolver_BiCGStab: Initial error (error0) =        3.185287126e-06
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 4.570507525e-17
MLCGSolver_BiCGStab: Initial error (error0) =        7.070533021e-07
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 1.286888373e-17
MLCGSolver_BiCGStab: Initial error (error0) =        1.539852001e-06
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 5.586691685e-17
MLCGSolver_BiCGStab: Initial error (error0) =        1.536488687e-06
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 1.292058631e-17
MLCGSolver_BiCGStab: Initial error (error0) =        1.327775287e-06
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 1.370561243e-17
MLCGSolver_BiCGStab: Initial error (error0) =        1.095398739e-06
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 1.359253986e-17
MLCGSolver_BiCGStab: Initial error (error0) =        8.886786415e-07
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 1.582357194e-17
MLCGSolver_BiCGStab: Initial error (error0) =        7.166210296e-07
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 3.116553327e-17
MLCGSolver_BiCGStab: Initial error (error0) =        5.767525712e-07
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 5.73681439e-18
MLCGSolver_BiCGStab: Initial error (error0) =        4.64021983e-07
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 2.495685334e-17
MLCGSolver_BiCGStab: Initial error (error0) =        3.734244751e-07
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 4.540999234e-17
MLCGSolver_BiCGStab: Initial error (error0) =        3.006619888e-07
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 2.338518159e-17
MLCGSolver_BiCGStab: Initial error (error0) =        2.42211391e-07
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 1.536803344e-17
MLCGSolver_BiCGStab: Initial error (error0) =        1.952329008e-07
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 1.694756589e-17
MLCGSolver_BiCGStab: Initial error (error0) =        1.574511012e-07
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 6.107276829e-17
MLCGSolver_BiCGStab: Initial error (error0) =        1.270459426e-07
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 5.290088246e-17
MLCGSolver_BiCGStab: Initial error (error0) =        1.025617416e-07
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 9.073346208e-18
MLCGSolver_BiCGStab: Initial error (error0) =        8.283360071e-08
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 2.122035969e-17
MLCGSolver_BiCGStab: Initial error (error0) =        6.692859985e-08
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 2.780808776e-17
MLCGSolver_BiCGStab: Initial error (error0) =        5.40989737e-08
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 2.19795691e-17
MLCGSolver_BiCGStab: Initial error (error0) =        4.37448624e-08
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 4.786392757e-17
MLCGSolver_BiCGStab: Initial error (error0) =        3.538466611e-08
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 4.383151853e-17
MLCGSolver_BiCGStab: Initial error (error0) =        2.863143121e-08
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 8.667194521e-17
MLCGSolver_BiCGStab: Initial error (error0) =        2.317402158e-08
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 3.234796462e-17
MLCGSolver_BiCGStab: Initial error (error0) =        1.876208967e-08
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 4.408787226e-17
MLCGSolver_BiCGStab: Initial error (error0) =        1.519406801e-08
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 2.636987073e-17
MLCGSolver_BiCGStab: Initial error (error0) =        1.230756437e-08
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 4.935669998e-17
MLCGSolver_BiCGStab: Initial error (error0) =        9.971672112e-09
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 1.166527262e-17
MLCGSolver_BiCGStab: Initial error (error0) =        8.080808095e-09
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 3.038919393e-17
MLCGSolver_BiCGStab: Initial error (error0) =        6.549770542e-09
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 9.866526612e-18
MLCGSolver_BiCGStab: Initial error (error0) =        5.309771728e-09
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 9.736536886e-18
MLCGSolver_BiCGStab: Initial error (error0) =        4.30525095e-09
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 3.15218139e-17
MLCGSolver_BiCGStab: Initial error (error0) =        3.491312422e-09
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 5.923135147e-17
MLCGSolver_BiCGStab: Initial error (error0) =        2.831663879e-09
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 7.987607584e-17
MLCGSolver_BiCGStab: Initial error (error0) =        2.296957117e-09
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 6.330237555e-17
MLCGSolver_BiCGStab: Initial error (error0) =        1.863451284e-09
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 1.387178423e-17
MLCGSolver_BiCGStab: Initial error (error0) =        1.5119354e-09
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 2.991955858e-17
MLCGSolver_BiCGStab: Initial error (error0) =        1.226859431e-09
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 4.477282495e-17
MLCGSolver_BiCGStab: Initial error (error0) =        9.956331663e-10
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 2.920811539e-17
MLCGSolver_BiCGStab: Initial error (error0) =        8.080602039e-10
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 3.998680113e-17
MLCGSolver_BiCGStab: Initial error (error0) =        6.5588087e-10
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 1.847424442e-17
MLCGSolver_BiCGStab: Initial error (error0) =        5.324028553e-10
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 1.213808016e-17
MLCGSolver_BiCGStab: Initial error (error0) =        4.322026524e-10
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 2.242818907e-17
MLCGSolver_BiCGStab: Initial error (error0) =        3.508841704e-10
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 2.992815652e-17
MLCGSolver_BiCGStab: Initial error (error0) =        2.848834728e-10
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 1.701313647e-17
MLCGSolver_BiCGStab: Initial error (error0) =        2.313107436e-10
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 8.730610113e-18
MLCGSolver_BiCGStab: Initial error (error0) =        1.878224857e-10
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 6.451252872e-17
MLCGSolver_BiCGStab: Initial error (error0) =        1.525179244e-10
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 2.913011461e-17
MLCGSolver_BiCGStab: Initial error (error0) =        1.238551572e-10
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 7.82649913e-17
MLCGSolver_BiCGStab: Initial error (error0) =        1.005832574e-10
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 1.30505273e-17
MLCGSolver_BiCGStab: Initial error (error0) =        8.168726106e-11
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 2.719435418e-17
MLCGSolver_BiCGStab: Initial error (error0) =        6.634356243e-11
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 8.142643056e-17
MLCGSolver_BiCGStab: Initial error (error0) =        5.388373963e-11
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 4.028943102e-17
MLCGSolver_BiCGStab: Initial error (error0) =        4.376532275e-11
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 1.211266124e-16
MLCGSolver_BiCGStab: Initial error (error0) =        3.554799307e-11
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 1.988352394e-17
MLCGSolver_BiCGStab: Initial error (error0) =        2.887431594e-11
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 1.049107408e-17
MLCGSolver_BiCGStab: Initial error (error0) =        2.345410514e-11
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 6.350143739e-17
MLCGSolver_BiCGStab: Initial error (error0) =        1.905178362e-11
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 5.299986495e-18
MLCGSolver_BiCGStab: Initial error (error0) =        1.547610181e-11
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 4.811836365e-17
MLCGSolver_BiCGStab: Initial error (error0) =        1.257176632e-11
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 8.031822521e-18
MLCGSolver_BiCGStab: Initial error (error0) =        1.021265614e-11
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 4.943581495e-17
MLCGSolver_BiCGStab: Initial error (error0) =        8.296372519e-12
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 2.586313063e-17
MLCGSolver_BiCGStab: Initial error (error0) =        6.739758112e-12
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 5.243655331e-17
MLCGSolver_BiCGStab: Initial error (error0) =        5.475286956e-12
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 5.186758761e-17
MLCGSolver_BiCGStab: Initial error (error0) =        4.448102505e-12
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 1.986294634e-17
MLCGSolver_BiCGStab: Initial error (error0) =        3.613658105e-12
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 7.422193798e-17
MLCGSolver_BiCGStab: Initial error (error0) =        2.935792174e-12
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 6.018983371e-17
MLCGSolver_BiCGStab: Initial error (error0) =        2.385113134e-12
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 2.645948803e-17
MLCGSolver_BiCGStab: Initial error (error0) =        1.937748486e-12
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 2.442610827e-17
MLCGSolver_BiCGStab: Initial error (error0) =        1.574304771e-12
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 2.405209217e-17
MLCGSolver_BiCGStab: Initial error (error0) =        1.279043097e-12
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 3.700551955e-17
MLCGSolver_BiCGStab: Initial error (error0) =        1.039158748e-12
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 4.858458636e-17
MLCGSolver_BiCGStab: Initial error (error0) =        8.442677551e-13
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 5.606237361e-18
MLCGSolver_BiCGStab: Initial error (error0) =        6.859341857e-13
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 5.750266728e-17
MLCGSolver_BiCGStab: Initial error (error0) =        5.573014615e-13
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 1.698601478e-17
MLCGSolver_BiCGStab: Initial error (error0) =        4.527924934e-13
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 4.181310866e-17
MLCGSolver_BiCGStab: Initial error (error0) =        3.678896723e-13
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 5.25350224e-17
MLCGSolver_BiCGStab: Initial error (error0) =        2.98902658e-13
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 8.181488991e-17
MLCGSolver_BiCGStab: Initial error (error0) =        2.428484298e-13
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 4.710132627e-17
MLCGSolver_BiCGStab: Initial error (error0) =        1.973186761e-13
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 2.998427167e-17
MLCGSolver_BiCGStab: Initial error (error0) =        1.603176248e-13
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 3.259905768e-17
MLCGSolver_BiCGStab: Initial error (error0) =        1.302517136e-13
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 5.14796889e-17
MLCGSolver_BiCGStab: Initial error (error0) =        1.05828717e-13
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 1.490825794e-17
MLCGSolver_BiCGStab: Initial error (error0) =        8.599077506e-14
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 2.178774001e-17
MLCGSolver_BiCGStab: Initial error (error0) =        6.986913945e-14
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 2.540373405e-17
MLCGSolver_BiCGStab: Initial error (error0) =        5.676346761e-14
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 4.342917078e-18
MLCGSolver_BiCGStab: Initial error (error0) =        4.612116863e-14
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 4.276024051e-17
MLCGSolver_BiCGStab: Initial error (error0) =        3.747147345e-14
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 4.736768729e-17
MLCGSolver_BiCGStab: Initial error (error0) =        3.044877501e-14
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 6.476951084e-17
MLCGSolver_BiCGStab: Initial error (error0) =        2.4744429e-14
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 5.8779384e-17
MLCGSolver_BiCGStab: Initial error (error0) =        2.010636558e-14
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 9.808596464e-18
MLCGSolver_BiCGStab: Initial error (error0) =        1.633110427e-14
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 6.943728558e-17
MLCGSolver_BiCGStab: Initial error (error0) =        1.326573928e-14
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 4.08828985e-17
MLCGSolver_BiCGStab: Initial error (error0) =        1.078007982e-14
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 3.54454241e-17
MLCGSolver_BiCGStab: Initial error (error0) =        8.756009267e-15
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 1.83002743e-17
MLCGSolver_BiCGStab: Initial error (error0) =        7.11359655e-15
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 7.797291005e-18
MLCGSolver_BiCGStab: Initial error (error0) =        5.774668518e-15
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 3.415178303e-17
MLCGSolver_BiCGStab: Initial error (error0) =        4.695089258e-15
MLCGSolver_BiCGStab: Final: Iteration    2 rel. err. 1.640803689e-17
MLMG: Failed to converge after 100 iterations. resid, resid/bnorm = 2.297383617e-09, 2.177631414e-12
amrex::Abort::22::MLMG failed. !!!
SIGABRT

WeiqunZhang Sep 29, 2025
Maintainer

Hypre should be more stable than MLMG. You should try to use hypre and tweak hypre's parameters.

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