Why does AMPL unexpectedly abort in the middle of doing something? I get a short error message, but I can’t find it explained in the AMPL book or in the solver documentation

You have encountered a low-level error message generated by the operating system. AMPL and the solvers try to trap these messages so as to provide you with more useful information instead; but occasionally a mysterious message does get through.

Some messages, such as

no children
unrecoverable error, STAT = 1001 
not enough swap space

usually indicate that AMPL can’t get enough computer resources to complete the current session. As an example, there might be insufficient disk space for AMPL to write the temporary file that the solver reads; to remedy the problem, you can reset option TMPDIR to change the directory to which temporary files are written. More often, however, the difficulty in this situation is insufficient memory, a more complicated matter that we discuss in the next question below.

Other messages, including

segmentation fault 
bus error

indicate a bug in AMPL or a solver. Often there is some way to work around this trouble temporarily, but you should also look for a more permanent fix. You can consult our bug fix log to see whether this bug has been found and fixed already; if not, you can tell us about the problem through our comment form. Either way, you will want to request a newer version of the AMPL software that incorporates the fix.