PETSc/TAO Users Manual: Revision 3.18

Abstract

the mechanisms needed within parallel application codes, such as parallel matrix and vector assembly routines. The library is organized hierarchically, enabling users to employ the level of abstraction that is most appropriate for a particular problem. By using techniques of object-oriented programming, PETSc provides enormous flexibility for users. PETSc is a sophisticated set of software tools; as such, for some users it initially has a much steeper learning curve than a simple subroutine library. In particular, for individuals without some computer science background, experience programming in C, C++, python, or Fortran and experience using a debugger such as gdb or dbx, it may require a significant amount of time to take full advantage of the features that enable efficient software use. However, the power of the PETSc design and the algorithms it incorporates may make the efficient implementation of many application codes simpler than “rolling them” yourself. • For many tasks a package such as MATLAB is often the best tool; PETSc is not intended for the classes of problems for which effective MATLAB code can be written. • There are several packages (listed on http://www.mcs.anl.gov/petsc), built on PETSc, that may satisfy your needs without requiring directly using PETSc. We recommend reviewing these packages functionality before using PETSc. • PETSc should not be used to attempt to provide a “parallel linear solver” in an otherwise sequential code. Certainly all parts of a previously sequential code need not be parallelized but the matrix generation portion must be parallelized to expect any kind of reasonable performance. Do not expect to generate your matrix sequentially and then “use PETSc” to solve the linear system in parallel. Since PETSc is under continued development, small changes in usage and calling sequences of routines will occur. PETSc is supported; see http://www.mcs.anl.gov/petsc/miscellaneous/mailinglists.html for information on contacting support. A list of publications and web sites that feature work involving PETSc may be found at http://www.mcs.anl.gov/petsc/publications. We welcome any reports of corrections for this document at petsc-maint@mcs.anl.gov.