[Trilinos-Users] [EXTERNAL] Belos PCG with ML preconditioner problem
Raymond Tuminaro
rstumin at sandia.gov
Tue Jul 8 17:38:14 MDT 2014
Markus,
This matrix looks pretty small to me. Could you just send it to me in a file (along with the right hand side)? I can
see if I have any troubles solving it ... and then we can work from there.
-Ray
On 07/08/14 15:54, Berndt, Markus wrote:
> We are having a problem with Belos PCG with ML preconditioning and I am hoping somebody on this list has an idea what
> might be wrong.
>
> The linear problem we are solving is symmetric positive definite (to be specific, it is the pressure projection
> equation). We are using the same matrix (an Epetra_FECrsMatrix) for Belos PCG as well as to initialize the ML
> preconditioner.
>
> During the CG iteration the code stops with the following exception:
>
> terminate called after throwing an instance of 'Belos::PCPGIterateFailure'
> what(): <...>/include/BelosPCPGIter.hpp:794:
>
> Throw number = 1
>
> Throw test that evaluated to true: alpha(0,0) <= zero
>
> Belos::CGIter::iterate(): non-positive value for alpha encountered!
>
> This is for pretty much any setup we choose for ML, except when we set number of levels = 1 and choose symmetric
> Gauss-Seidel as a coarse grid solver (or other symmetric smoothers). This should result in a symmetric preconditioner
> and it does indeed. As soon as we set the max number of levels > 1, we see the error above.
>
> In the rest of this email I am attaching some debug output that includes the all the parameters used for ML setup. We
> think we should have set things up such that the ML preconditioner should be symmetric, but perhaps there is a problem.
> We don't see it.
>
> We appreciate any help!
>
> Thanks
>
> - Markus
>
> ------------------------------------------------------------------------------
> Using `cg' for eigen-computations
> ***
> *** ML_Epetra::MultiLevelPreconditioner
> ***
> Matrix has 242 rows and 3.8440e+03 nonzeros, distributed over 1 process(es)
> The linear system matrix is an Epetra_CrsMatrix
> ** Leaving column map of Main linear system matrix unchanged
> Default values for `SA'
> Maximum number of levels = 10
> Using increasing levels. Finest level = 0, coarsest level = 9
> Number of applications of the ML cycle = 1
> Number of PDE equations = 1
> Aggregation threshold = 0.0000e+00
> Max coarse size = 16
> R and P smoothing : P = (I-\omega A) P_t, R = P^T
> R and P smoothing : \omega = 1.3330e+00/lambda_max
> Null space type = default (constants)
> Null space dimension = 1
> -----------------------------------------------------------------------
> ML_Gen_MultiLevelHierarchy (level 0) : Gen Restriction and Prolongator
> -----------------------------------------------------------------------
> ML_Aggregate_Coarsen (level 0) begins
> ML_Aggregate_CoarsenMIS : current level = 0
> ML_Aggregate_CoarsenMIS : current eps = 0.000000e+00
> Aggregation(MIS) : Total nonzeros = 3844 (Nrows=242)
> Aggregation(MIS) : Phase 1 - nodes aggregated = 242
> Aggregation(MIS) : Phase 1 - total aggregates = 16
> Aggregation(MIS) : Phase 2a- additional aggregates = 0
> Aggregation(MIS) : Phase 2 - total aggregates = 16
> Aggregation(MIS) : Phase 2 - boundary nodes = 0
> Aggregation(MIS) : Phase 3 - leftovers = 0 and singletons = 0
> Communicating phase 2/3 info
> Calling ML_Operator_UnAmalgamateAndDropWeak
> Aggregation(MIS) : QR factorization - too small aggregates = 0
> Gen_Prolongator (level 0) : Max eigenvalue = 2.1838e+00
>
> Prolongator/Restriction smoother (level 0) : damping factor #1 = 6.1041e-01
> Prolongator/Restriction smoother (level 0) : ( = 1.3330e+00 / 2.1838e+00)
>
> Smoothed Aggregation : operator complexity = 1.026015e+00.
> Time to build the hierarchy = 2.1720e-03 (s)
> Number of actual levels : 2
>
> Smoother (level 0) : # global rows = 2.e+02, # estim. global nnz = 4.e+03, # nnz
> per row = 16.
> Smoother (level 0) : IFPACK, type=`IC',
> Smoother (level 0) : both,overlap=0
> Smoother (level 0) : level-of-fill=0.0000e+00,rel. threshold=1.0000e+00,abs.
> threshold=0.0000e+00
> Smoother (level 0) : Setup time : 6.2299e-04 (s)
>
> WARNING **********************************************************************
> You have requested to keep the finest level smoother from a previous
> solve. In order to reuse part or all of the incomplete factorization
> from smoother "IC", you must also specify the smoother options
> "reuse numeric factorization" and/or "reuse symbolic factorization".
> Not doing so may result in memory leaks or crashes.
>
> Amesos (level 1) : NumGlobalRows = 16
> Amesos (level 1) : NumGlobalNonzeros = 100
> Amesos (level 1) : Fill-in = 3.9062e+01 %
> Amesos (level 1) : Building KLU
> Amesos (level 1) : Time for factorization = 8.2016e-05 (s)
>
> WARNING: Parameter "ML print final list" -1 [unused] is unused
> WARNING: Parameter "coarse: list" [unused] is unused
> WARNING: Parameter "aggregation: list (level 0)" [unused] is unused
> WARNING: Parameter "aggregation: list (level 1)" [unused] is unused
> WARNING: Parameter "aggregation: list (level 2)" [unused] is unused
> WARNING: Parameter "aggregation: list (level 3)" [unused] is unused
> WARNING: Parameter "aggregation: list (level 4)" [unused] is unused
> WARNING: Parameter "aggregation: list (level 5)" [unused] is unused
> WARNING: Parameter "aggregation: list (level 6)" [unused] is unused
> WARNING: Parameter "aggregation: list (level 7)" [unused] is unused
> WARNING: Parameter "aggregation: list (level 8)" [unused] is unused
> WARNING: Parameter "aggregation: list (level 9)" [unused] is unused
> WARNING: Parameter "smoother: list (level 0)" [unused] is unused
> ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> +++ Printing ML parameter list "SA default values" on pid 0
> ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> default values = SA
> max levels = 10
> prec type = MGV
> increasing or decreasing = increasing
> aggregation: type = Uncoupled-MIS
> aggregation: damping factor = 1.3330e+00
> eigen-analysis: type = cg
> eigen-analysis: iterations = 10
> smoother: sweeps = 1
> smoother: damping factor = 1.0000e+00
> smoother: pre or post = both
> smoother: type = IC
> ML output = 10
> print unused = -1
> ML print initial list = -1
> ML print final list = -1
> read XML = 0 [default]
> ML debug mode = 0 [default]
> output prefix = [default]
> analyze memory = 0 [default]
> cycle applications = 1 [default]
> zero starting solution = 1 [default]
> ML label = not-set [default]
> low memory usage = 0 [default]
> PDE equations = 1 [default]
> ML validate depth = 5 [default]
> ML validate parameter list = 1 [default]
> profile: operator iterations = 0 [default]
> filter: type = 0 [default]
> filter: mask = 0 [default]
> use crs matrix storage = 0 [default]
> aggregation: aggressive = 5.0000e-01 [default]
> aggregation: threshold = 0.0000e+00 [default]
> aggregation: next-level aggregates per process = 128 [default]
> aggregation: symmetrize = 0 [default]
> energy minimization: enable = 0 [default]
> aggregation: smoothing sweeps = 1 [default]
> R and P smoothing: type = classic [default]
> aggregation: aux: enable = 0 [default]
> aggregation: block scaling = 0 [default]
> aggregation: use tentative restriction = 0 [default]
> null space: type = default vectors [default]
> null space: scaling = 0 [default]
> x-coordinates = 0 [default]
> y-coordinates = 0 [default]
> z-coordinates = 0 [default]
> repartition: enable = 0 [default]
> smoother: Aztec options = Teuchos::RCP<std::vector<int, std::allocator<int> >
> >{ptr=0x3935640,node=0x3935660,strong_count=2,weak_count=0} [default]
> smoother: Aztec params = Teuchos::RCP<std::vector<double, std::allocator<double> >
> >{ptr=0x39356a0,node=0x39356c0,strong_count=2,weak_count=0} [default]
> smoother: Aztec as solver = 0 [default]
> smoother: MLS polynomial order = -97 [default]
> smoother: polynomial order = -97 [default]
> smoother: MLS alpha = -2.0000e+00 [default]
> smoother: Chebyshev alpha = -2.0000e+00 [default]
> smoother: ParaSails levels = 0 [default]
> smoother: ParaSails matrix = 0 [default]
> smoother: ParaSails threshold = 1.0000e-02 [default]
> smoother: ParaSails filter = 5.0000e-02 [default]
> smoother: ParaSails load balancing = 0.0000e+00 [default]
> smoother: ParaSails factorized = 0 [default]
> smoother: ifpack type = Amesos [default]
> smoother: ifpack overlap = 0 [default]
> smoother: ifpack level-of-fill = 0.0000e+00 [default]
> smoother: ifpack relative threshold = 1.0000e+00 [default]
> smoother: ifpack absolute threshold = 0.0000e+00 [default]
> smoother: Block Chebyshev number of blocks = -1 [default]
> smoother: Block Chebyshev block list = 0 [default]
> smoother: Block Chebyshev block starts = 0 [default]
> smoother: chebyshev solve normal equations = 0 [default]
> filtering: enable = 0 [default]
> dump matrix: enable = 0 [default]
> print hierarchy = -2 [default]
> reuse: enable = 0 [default]
> coarse: list ->
> smoother: type = Amesos-KLU
> smoother: max size = 16
> smoother: pre or post = post
> smoother: sweeps = 1
> smoother: damping factor = 1 [default]
> smoother: add to diag = 1e-12 [default]
> aggregation: list (level 0) ->
> aggregation: type = Uncoupled-MIS [default]
> aggregation: smoothing sweeps = 1 [default]
> aggregation: list (level 1) ->
> aggregation: type = Uncoupled-MIS [default]
> aggregation: smoothing sweeps = 1 [default]
> aggregation: list (level 2) ->
> aggregation: type = Uncoupled-MIS [default]
> aggregation: smoothing sweeps = 1 [default]
> aggregation: list (level 3) ->
> aggregation: type = Uncoupled-MIS [default]
> aggregation: smoothing sweeps = 1 [default]
> aggregation: list (level 4) ->
> aggregation: type = Uncoupled-MIS [default]
> aggregation: smoothing sweeps = 1 [default]
> aggregation: list (level 5) ->
> aggregation: type = Uncoupled-MIS [default]
> aggregation: smoothing sweeps = 1 [default]
> aggregation: list (level 6) ->
> aggregation: type = Uncoupled-MIS [default]
> aggregation: smoothing sweeps = 1 [default]
> aggregation: list (level 7) ->
> aggregation: type = Uncoupled-MIS [default]
> aggregation: smoothing sweeps = 1 [default]
> aggregation: list (level 8) ->
> aggregation: type = Uncoupled-MIS [default]
> aggregation: smoothing sweeps = 1 [default]
> aggregation: list (level 9) ->
> aggregation: smoothing sweeps = 1 [default]
> smoother: list (level 0) ->
> smoother: sweeps = 1 [default]
> smoother: damping factor = 1 [default]
> smoother: pre or post = both [default]
> smoother: type = IC [default]
> smoother: add to diag = 1e-12 [default]
> smoother: ifpack level-of-fill = 0 [default]
> smoother: ifpack overlap = 0 [default]
> smoother: ifpack relative threshold = 1 [default]
> smoother: ifpack absolute threshold = 0 [default]
> smoother: ifpack list ->
> ILU: sweeps = 1 [unused]
> partitioner: map = 0x39432d8 [unused]
> fact: level-of-fill = 0
> fact: relative threshold = 1 [unused]
> fact: absolute threshold = 0 [unused]
> -------------------------------------------------
> ----------- end of ML parameter list ------------
> -------------------------------------------------
>
> Cumulative timing for construction so far:
> - for initial setup = 5.0602e-03 (s)
> - for hierarchy setup = 2.1951e-03 (s)
> - for smoothers setup = 6.2299e-04 (s)
> - for coarse setup = 2.3699e-04 (s)
> - for final setup = 6.2203e-04 (s)
> Total for this setup = 8.9622e-03 (s)
> ------------------------------------------------------------------------------
> ============ ML ============
>
> ============ Belos ============
> Block Size = 1 [unused]
> Maximum Iterations = 250 [unused]
> Convergence Tolerance = 1.0000e-12 [unused]
> Verbosity = 59 [unused]
> Output Frequency = 1 [unused]
>
> Belos::StatusTestGeneralOutput: Failed
> (Num calls,Mod test,State test): (1, 1, Passed Failed Undefined)
> Failed.......OR Combination ->
> OK...........Number of Iterations = 0 < 250
> Unconverged..(2-Norm Imp Res Vec) / (2-Norm Res0)
> residual [ 0 ] = 1.0000e+00 > 1.0000e-12
>
>
> Belos::StatusTestGeneralOutput: Failed
> (Num calls,Mod test,State test): (2, 1, Passed Failed Undefined)
> Failed.......OR Combination ->
> OK...........Number of Iterations = 1 < 250
> Unconverged..(2-Norm Imp Res Vec) / (2-Norm Res0)
> residual [ 0 ] = 9.5492e-01 > 1.0000e-12
>
> terminate called after throwing an instance of 'Belos::PCPGIterateFailure'
> what(): <...>/include/BelosPCPGIter.hpp:794:
>
> Throw number = 1
>
> Throw test that evaluated to true: alpha(0,0) <= zero
>
> Belos::CGIter::iterate(): non-positive value for alpha encountered!
> ============ Belos ============
>
>
>
> --
> Markus Berndt -- LANL CCS-2 -- 505-665-4711
>
>
> _______________________________________________
> Trilinos-Users mailing list
> Trilinos-Users at software.sandia.gov
> https://software.sandia.gov/mailman/listinfo/trilinos-users
>
--
Ray Tuminaro phone: (925) 294-2564
MS 9159 fax: (925) 294-2234
Sandia National Laboratories email: rstumin at sandia.gov
PO Box 969 http://www.cs.sandia.gov/~rstumin
Livermore, CA 94551
More information about the Trilinos-Users
mailing list