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# Troubleshooting

Successful installation, testing, and use of ScaLAPACK rely heavily on the proper installation of its building blocks (PVM or MPI, BLACS, BLAS, and PBLAS). Frequently Asked Questions (FAQ) lists are maintained in the directories on netlib to answer some of the most common user questions. For the user's convenience, prebuilt ScaLAPACK and BLACS libraries are provided for a variety of computer architectures in the following URLs:

> `http://www.netlib.org/scalapack/archives/`
> `http://www.netlib.org/blacs/archives/`

Test suites are provided for PVM, the BLACS, the BLAS, and the PBLAS. It is highly recommended that each of these respective test suites be run prior to the execution of the ScaLAPACK test suite. Installation Guides are also provided for the BLACS and ScaLAPACK. Refer to the appropriate directory on netlib for further information.

We begin this chapter by discussing a set of first-step debugging hints to pinpoint where the problem is occurring. Following these debugging hints, we discuss the types of error messages that can be encountered during the execution of a ScaLAPACK routine: ScaLAPACK error messages, PBLAS error messages, BLACS error messages, and system-dependent error messages or failures.

If these suggestions do not help evaluate specific difficulties, we suggest that the user review the following ``bug report checklist'' and then feel free to contact the authors at `scalapack@cs.utk.edu` or `blacs@cs.utk.edu`, respectively. The user should tell us the type of machine on which the tests were run, the compiler and compiler options that were used, details of the BLACS library and message-passing library that were used and the BLAS library; also, the user should send a copy of the input file, if appropriate.

- Installation Debugging Hints
- Application Debugging Hints
- Common Errors in Calling ScaLAPACK Routines
- Failures Detected by ScaLAPACK Routines
  - Invalid Arguments and PXERBLA
  - Computational Failures and INFO > 0
- Wrong Results
- Error Handling in the PBLAS
- Error Handling in the BLACS
  - BLACS Warning and Error Messages
- System Error Messages
- Poor Performance