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Computational Failures and INFO > 0

   A positive value of INFO on return from a ScaLAPACK routine indicates a failure in the course of the algorithm. Common causes are

For example, if PSGESVX  is called to solve a system of equations with a coefficient matrix  that is approximately singular, it may detect exact singularity at the ith stage of the LU factorization, in which case it returns INFO = i; or (more probably) it may compute an estimate of the reciprocal condition number that is less than relative machine precision, in which case it returns INFO = n+1. Again, the documentation in Part ii should be consulted for a description of the error.

When a failure with INFO > 0 occurs, control is always returned to the calling program; PXERBLA() is not called, and no error message is written. Thus, it is always good practice to check for a nonzero value of INFO on return from a ScaLAPACK routine.

A failure with INFO > 0 may indicate any of the following:


next up previous contents index
Next: Wrong Results Up: Failures Detected by ScaLAPACK Previous: Invalid Arguments and PXERBLA

Susan Blackford
Tue May 13 09:21:01 EDT 1997