Using PyTrilinos: A Tutorial

1
Using PyTrilinosA Tutorial

• Bill Spotz
• Sandia National Laboratories
• 2006 Trilinos Users Group Meeting
• Nov 8, 2006

2
Outline

• Building PyTrilinos (Teuchos Epetra only)
• Installing PyTrilinos
• Getting help for PyTrilinos
• An interactive exploration of Epetra
• Parameter lists
• Writing scripts to solve problems

3
Building PyTrilinos

• Configure script
• Take a working configure script, and just add
• --enable-python
• For our purposes, restrict to Teuchos and Epetra
• --disable-default-packages \
• --enable-teuchos \
• --enable-epetra
• You may need to be explicit about the C
  compiler
• CXXg
• Think about where you want to install
• --prefixPREFIX
• Building
• Invoking configure and make should do the trick

4
Installing PyTrilinos

• Install command
• sudo make install
• If no prefix specified, then PyTrilinos is
  installed where your python knows to find it
• If you specified prefix, then you need to tell
  python how to find the PyTrilinos package
• Environment variables
• LD_LIBRARY_PATHPREFIX/lib
• PYTHONPATHPREFIX/lib/python2.4/site-packages
• Within python (e.g. .pythonrc)
• import sys
• sys.path.append("PREFIX/lib/python2.4/site-package
  s")
• Try it
• python
• gtgtgt from PyTrilinos import Epetra

5
Getting Help

• From shell
• pydoc PyTrilinos
• From python
• python
• gtgtgt from PyTrilinos import Epetra
• gtgtgt help(Epetra)
• gtgtgt dir(Epetra)
• From web site
• FAQ
• Overview
• Release 7.0 (including tutorial)
• Development (including tutorial)
• Trilinos doxygen pages
• Submitting bugs
• Under bugzilla, submit to the appropriate
  Trilinos package, specifying the Python
  wrappers component

6
Exploring Epetra Interactively

• Communicators
• Printing Epetra objects
• Maps
• C-arrays as return objects
• Vectors
• NumPy hybrids
• MultiVectors
• CrsMatrix objects

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Parameter Lists

• Old school
• gtgtgt from PyTrilinos import Teuchos
• gtgtgt pList Teuchos.ParameterList()
• gtgtgt pList.set("one", 1)
• gtgtgt . . .
• Python dictionaries can be used in place of
  ParameterLists
• Keys must be strings
• Values must be bool, int, float, str, or dict (or
  ParameterList)
• gtgtgt pList "one" 1, "two" 2
• Returned ParameterLists are actually
  PyDictParameterLists

8
Writing Scripts

• Feel free to tackle your own problem
• Write a function that returns your favorite
  Epetra.CrsMatrix
• Suggestion Power method (see software.sandia.gov/
  Trilinos/packages/docs/dev/ packages/epetra/doc/h
  tml/ index.html)
• Alternatively CG algorithm (from GvL)