[Trilinos-Users] small question concerning ML
Riccardo Rossi
rrossi at cimne.upc.edu
Thu Mar 21 03:40:41 MDT 2013
Dear list,
i am trying to use ILU0 smoother together with ML to see if it can improve
convergence, with a problem which corresponds to a pde size of 4
the thing is that if i use the following
ML_Epetra::SetDefaults("NSSA", MLList, options, params);
MLList.set("PDE equations", mNumDof);
MLList.set("null space: add default vectors", true);
MLList.set("aggregation: type","Uncoupled");
it works correctly
but if i put the following settings
MLList.set("PDE equations", mNumDof);
MLList.set("null space: add default vectors", true);
MLList.set("aggregation: type","Uncoupled"); <----- up to this
point exactly identical
MLList.set("smoother: type","IFPACK");
MLList.set("smoother: ifpack type", "ILU");
MLList.set("smoother: ifpack overlap", 0);
MLList.sublist("smoother: ifpack list").set("fact: level-of-fill",
0);
MLList.set("ML output",5);
MLList.set("print unused",1);
than it does not even try to iterate and gives the output posted at the end
of the email (provding at the end a wrong result):
can anyone give a hint of what can i be doing wrong? changing overlap and
level of fill does not improve the situation
also commenting the line
MLList.set("null space: add default vectors", true);
does not help
any suggestion is welcome
thank you in advance
Riccardo
System Solve Time : 5.44
Building Time : 2.86
ML_Aggregate_Coarsen (level 0) begins
ML_Aggregate_CoarsenUncoupled : current level = 0
ML_Aggregate_CoarsenUncoupled : current eps = 0.000000e+00
Aggregation(UVB) : Total nonzeros = 25542464 (Nrows=438016)
Aggregation(UVB) : Amalgamated matrix done
Aggregation(UC) : Phase 0 - no. of bdry pts = 0
Aggregation(UC) : Phase 1 - nodes aggregated = 71810 (109504)
Aggregation(UC) : Phase 1 - total aggregates = 5698
Aggregation(UC_Phase2_3) : Phase 1 - nodes aggregated = 71027
Aggregation(UC_Phase2_3) : Phase 1 - total aggregates = 5698
Aggregation(UC_Phase2_3) : Phase 2a- additional aggregates = 237
Aggregation(UC_Phase2_3) : Phase 2 - total aggregates = 5935
Aggregation(UC_Phase2_3) : Phase 2 - boundary nodes = 1226
Aggregation(UC_Phase2_3) : Phase 3 - leftovers = 0 and singletons = 0
ML_Aggregate_Coarsen (level 1) begins
ML_Aggregate_CoarsenUncoupled : current level = 1
ML_Aggregate_CoarsenUncoupled : current eps = 0.000000e+00
Aggregation(UVB) : Total nonzeros = 4840413 (Nrows=23740)
Aggregation(UVB) : Amalgamated matrix done
Aggregation(UC) : Phase 0 - no. of bdry pts = 0
Aggregation(UC) : Phase 1 - nodes aggregated = 3526 (5935)
Aggregation(UC) : Phase 1 - total aggregates = 97
Aggregation(UC_Phase2_3) : Phase 1 - nodes aggregated = 3526
Aggregation(UC_Phase2_3) : Phase 1 - total aggregates = 97
Aggregation(UC_Phase2_3) : Phase 2a- additional aggregates = 25
Aggregation(UC_Phase2_3) : Phase 2 - total aggregates = 122
Aggregation(UC_Phase2_3) : Phase 2 - boundary nodes = 2
Aggregation(UC_Phase2_3) : Phase 3 - leftovers = 0 and singletons = 0
ML_Aggregate_Coarsen (level 2) begins
ML_Aggregate_CoarsenUncoupled : current level = 2
ML_Aggregate_CoarsenUncoupled : current eps = 0.000000e+00
Aggregation(UVB) : Total nonzeros = 97790 (Nrows=488)
Aggregation(UVB) : Amalgamated matrix done
Aggregation(UC) : Phase 0 - no. of bdry pts = 0
Aggregation(UC) : Phase 1 - nodes aggregated = 94 (122)
Aggregation(UC) : Phase 1 - total aggregates = 5
Aggregation(UC_Phase2_3) : Phase 1 - nodes aggregated = 94
Aggregation(UC_Phase2_3) : Phase 1 - total aggregates = 5
Aggregation(UC_Phase2_3) : Phase 2a- additional aggregates = 1
Aggregation(UC_Phase2_3) : Phase 2 - total aggregates = 6
Aggregation(UC_Phase2_3) : Phase 2 - boundary nodes = 0
Aggregation(UC_Phase2_3) : Phase 3 - leftovers = 0 and singletons = 0
Smoothed Aggregation : operator complexity = 1.193356e+00.
Amesos (level 3) : NumGlobalRows = 24
Amesos (level 3) : NumGlobalNonzeros = 576
Amesos (level 3) : Fill-in = 100 %
Amesos (level 3) : Building KLU
Amesos (level 3) : Time for factorization = 0.000393867 (s)
*******************************************************
***** Problem: Epetra::CrsMatrix
***** Preconditioned GMRES (with condnum) solution
***** ML (L=4, ~/IFPACK_post0, ~/Amesos_KLU_3)
***** No scaling
*******************************************************
iter: 0 residual = 1.000000e+00
***************************************************************
Warning: the GMRES Hessenberg matrix is ill-conditioned. This may
indicate that the application matrix is singular. In this case, GMRES
may have a least-squares solution.
Solver: gmres_condnum
number of iterations: 1
Actual residual = 3.0313e+00 Recursive residual = 3.0313e+00
Calculated Norms Requested Norm
-------------------------------------------- --------------
||r||_2 / ||r0||_2: 1.000000e+00 1.000000e-08
-----------------------------------------------------
Warning : The Hessenberg matrix is too small
Analysis of the Hessenberg matrix:
smallest eigenvalue (in module) = 1.000000e+00
largest eigenvalue (in module) = 1.000000e+00
***************************************************************
estimated condition number = 1.000000e+00
-----------------------------------------------------
Solution time: 0.594218 (sec.)
total iterations: 1
Linear solver
--
Dr. Riccardo Rossi, Civil Engineer
Member of Kratos Team
International Center for Numerical Methods in Engineering - CIMNE
Campus Norte, Edificio C1
c/ Gran Capitán s/n
08034 Barcelona, España
Tel: (+34) 93 401 56 96
Fax: (+34) 93.401.6517
web: www.cimne.com
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