The error handling in AMG4PSBLAS is based on the PSBLAS error handling. Error conditions are signaled via an integer argument info; whenever an error condition is detected, an error trace stack is built by the library up to the top-level, user-callable routine. This routine will then decide, according to the user preferences, whether the error should be handled by terminating the program or by returning the error condition to the user code, which will then take action, and whether an error message should be printed. These options may be set by using the PSBLAS error handling routines; for further details see the PSBLAS User’s Guide [21].