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Amesos Interfaces to sparse direct solvers

Amesos Interfaces to sparse direct solvers. October 15, 2003 8:30 – 9:30 a.m. Ken Stanley. Overview. Background Simplifying AX = B Getting started: Amesos_Umfpack Amesos options Other Amesos interfaces Status Future Work and Discussion Summary. Background. Solvers Sandia Users

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Amesos Interfaces to sparse direct solvers

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  1. AmesosInterfaces to sparse direct solvers October 15, 2003 8:30 – 9:30 a.m. Ken Stanley

  2. Overview • Background • Simplifying AX = B • Getting started: Amesos_Umfpack • Amesos options • Other Amesos interfaces • Status • Future Work and Discussion • Summary

  3. Background • Solvers • Sandia Users • Challenges

  4. Background - Solvers • PSPACES [Gupta]; f90; mpi; SPD; unsupported • WSSMP [Gupta]; binary; mpi; general; • WGSMP [Gupta]; binary; mpi; SPD • SPOOLES [Ashcraft];public domain;c; unsupported • SuperLU [Li,Demmel];serial;c;general • UMFPACK [Davis];serial;c;general;robust • Unnamed [Ng];parallel;f77;SPD; • MUMPS [Amestoy];f90;general/SPD; • Ksparse [Kundert]; • SNL_MPFRONT [Benner];parallel • OTHERS: y12M, Boeing, MA57, MA43, DPSLDLT, DPSLDU, PARDISO, Shen, Dearholt, SPLU, Lusol, LUSOL, XYT

  5. Background – Sandia Users • Tuminaro – ML, etc. • Shadid – MP Salsa • Williams – Sierra • Hoekstra – Xyce • Pierson – • Dohrman – • Schultz - GOMA • Many – Aztec • Many more

  6. Background - Challenges • No single solver dominates • Different interfaces • Unique data distribution requirements • Academic quality • Sporadic development, bugs, untested features, changing interfaces • Sandia modifications not consistently adopted • Imperfect heuristics • Interface changes between revisions

  7. Simplifying AX = B • Example • Clean, consistent interface • Single point of contact • Evaluation

  8. Simplifying AX = BExample Epetra_LinearProblem Problem( A, x, b); Amesos_Umfpack A_direct( Problem, ParamList ) ; A_direct.SymbolicFactorization( ) ; A_direct.NumericFactorization( ) ; A_direct.Solve( ) ;

  9. Simplifying AX = B Single point of contact • Isolate; report bugs; follow-up • Prompt bug fixes without maintaining third party code • Encourage developers to adopt Trilinos practices • Autotools; CVS; regression testing; bug tracking; etc. • Regression testing • Check for memory leaks

  10. Simplifying AX = B Evaluation • Solvers • Platforms • Matrices • Features • Our goal is to find the bugs before you do

  11. Getting started: Building Umfpack • Amesos User Guide: http://software.sandia.gov/trilinos/packages/amesos • Build UMFPACK • Download from UMFPACK website • Modify make.inc (see: Trilinos3PL/config/UMFPACKv4.1) • “make” ; Check output of example run • Future Work • autotool UMFPACK; • Trilinos/packages/UMFPACK ? • -lumfpack?

  12. Getting started: Building Amesos_Umfpack • Amesos User Guide: http://software.sandia.gov/trilinos/packages/amesos • Build Amesos_Umfpack • “./configure –enable-amesos –enable-amesos-umfpack –with-trilinos3PLdir=/home/userid/Trilinos3PL” • “make” • “cd amesos/test; source AmesosUmfpackShort.exe”

  13. Getting started: Calling Amesos_Umfpack Epetra_CrsMatrix A; Epetra_Vector x, b; AMESOS::Parameter::List ParamList ; Epetra_LinearProblem Problem( A, x, b); Amesos_Umfpack A_direct( Problem, ParamList ) ; A_direct.SymbolicFactorization( ) ; A_direct.NumericFactorization( ) ; A_direct.Solve( ) ; Future Work: Factory Method, Trilinos::Parameter::List

  14. Amesos options • Same structure different data • Multiple solves • Blocked right hand sides • Parameter control • Different solver • Matrix format

  15. Amesos options: Same Structure Different Data Epetra_LinearProblem Problem( A, x, b); Amesos_Umfpack A_direct( Problem, ParamList ) ; A_direct.SymbolicFactorization( ) ; for ( ) { // Modifications to the non-zero values of A A_direct.NumericFactorization( ) ; A_direct.Solve( ) ; }

  16. Amesos options: Multiple Solves Epetra_LinearProblem Problem( A); Amesos_Umfpack A_direct( Problem, ParamList ) ; A_direct.SymbolicFactorization( ) ; A_direct.NumericFactorization( ) ; for ( ) { Problem.SetLHS(x); Problem.SetRHS(b); A_direct.Solve( ) ; }

  17. Amesos Options: Blocked right hand sides Epetra_CrsMatrix A; Epetra_MultiVector x, b; AMESOS::Parameter::List ParamList ; Epetra_LinearProblem Problem( A, x, b); Amesos_Umfpack A_direct( Problem, ParamList ) ; A_direct.SymbolicFactorization( ) ; A_direct.NumericFactorization( ) ; A_direct.Solve( ) ;

  18. Amesos Options: Parameter control Epetra_LinearProblem Problem( A, x, b); Amesos_UmfpackA_direct( Problem, ParamList ) ; A_direct.SymbolicFactorization( ) ; ParamList.SetParam( “UmfpackOrder”, 2 ); for ( ) { // Modifications to the non-zero values of A A_direct.NumericFactorization( ) ; A_direct.Solve( ) ; }

  19. Amesos Options: Matrix format • Interface accepts any Epetra_RowMatrix • Current implementation accepts any Epetra_CrsMatrix

  20. Other Amesos Interfaces • Klu – Serial, unblocked, for circuit matrices • SuperLUdist – Distributed; limited Amesos release • MUMPS – Distributed; F90; limited Amesos release • DSCPACK – Distributed; Symmetric • Use distributed code for problems • that are too large to solve on one processor -or- • take more than one minute to factor • Others – WSMP, Benner, Ksparse, Ng

  21. Status • Nightly testing on four platforms: • Atlantis/IRIX, • Stratus/OSF, • Herouxsmp/Linux, • Paunchy/SunOS • Full support for three packages: Amesos_Umfpack, Amesos_Klu and Amesos_Dscpack • Other packages: Epetra_SLU, SuperludistOO, Amesos_Mumps, Amesos_Superludist • One example code: example/AmesosDscpack

  22. Future Work • Capabilities • Ease of use • Single point of contact

  23. Future Work - Capabilities • Amesos_Superludist • Amesos_Mumps, Amesos_SuperLU, Amesos_Ksparse, Amesos_Benner, Amesos_Ng, Amesos_Wsmp • Expose capabilities to users • Support transpose for all solvers • Support row matrix interface • Support Epetra_VbrMatrix in DSCPACK • Extra precision iterative refinement

  24. Future Work – Ease of use • Examples (TSF extended; TSF core; etc.) • Pre-built libraries? (-lamesos, -lumfpack, -lsuperludist) • Autotools use by third party developers • Factory Method

  25. Future Work – Single point of contact • Encourage developers to adopt Trilinos practices • Autotools; CVS; regression testing; bug tracking; nightly testing; etc. • Trilinos package? • Isolate, report bugs, follow-up • Migration to latest revisions • Add testing based on the Amesos_BaseSolver class • More features • More matrices • Parameter control • Test error conditions

  26. Discussion • Your needs? • Platforms • Packages • Features • Interface

  27. Amesos Value Added • Simple, consistent interface • Short learning curve • Easy to switch solvers • Interface to third party developers • Evaluation • Bug workarounds

  28. Summary • Amesos is driven by your needs • Tell me what you need • Give me your matrices • Simple, consistent interface • Start with Amesos_Umfpack • Switch to parallel codes for large matrices • Matrices that don’t fit in memory • Factorizations that take over a minute • Experiment with different solvers

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