72.19 If Things Go Wrong

This section lists a few common problems when installing or running GAP and their remedies:

GAP starts with a warning ``hmm, I cannot find 'lib/init.g'''.

You either started only the binary or did not edit the shell script/batch file to give the correct library path. You must start the binary with the command line option -l path where path is the path to the GAP home directory. See section Command Line Options in the reference manual.

When starting, GAP produces error messages about undefined variables.

You might have a .gaprc file that was intended for GAP 3 but is not compatible with GAP 4. See section The .gaprc file in chapter Running GAP of the reference manual.

GAP stops with an error message: ``cannot extend the workspace any more''.

Your calculation exceeded the available memory. Most likely you asked GAP to do something which required more memory than you have (as listing all elements of S₁₅ for example). You can use the command line option -g (see section Command Line Options in the reference manual) to display how much memory GAP uses. If this is below what your machine has available (this happens for example under Windows) extending the workspace is impossible. Start GAP with more memory or use the -a option to pre-allocate initially a large piece of workspace.

GAP complains: ``corrupted completion file''.

Some library files got changed without rebuilding the completion files. This is often a sign that earlier bugfixes were not installed properly or that you changed the library yourself. In th elatter case, start GAP with command line option -N and see section Completion Files.

GAP stops with an error message ``exceeded the permitted memory''.

Your job got bigger than what is permitted by default (128MB). (This is a safety feature to avoid singe jobs wrecking a multi-user system.) You can type return; to continue, if the error message happens repeatedly you better start the job anew and use the command line option -o to set a higher memory limit.

make complains about not being able to find files in cnf or src which

exist.

The dates of the new files were not extracted properly (Alpha-OSF machines are prone to this). Call

touch * cnf/* src/*

from the main GAP directory (this ought to reset the date of all relevant files to ``now'') and try again.

Recompilation does not actually compile changed files.

The dates of the new files were not extracted properly. Go in the source directory and touch (UNIX command to change date) the new files.

Recompilation fails or the new binary crashes.

Call make clean and restart the configure / make process completely from scratch. (It is possible that the operating system and/or compiler got upgraded in the meantime and so the existing .o files cannot be used any longer.

A calculation runs into an error ``no method found''.

GAP is not able to execute a certain operation with the given arguments. Besides the possibility of bugs in the library this means two things: Either GAP truely is incapable of coping with this task (the objects might be too complicated for the existing algorithms or there might be no algorithm that can cope with the input). Another possibility is that GAP does not know that the objects have certain nice properties (like being finite) which are required for the available algorithms. See sections ApplicableMethod and KnownPropertiesOfObject.

Problems specific to Windows

The gap.bat file does not start GAP.

Make sure you ran instwin.bat. If your version of Windows uses a language other than English you must still edit the resulting file gap.bat in the bin subdirectory, due to a misdesign of Windows.

Windows complains Out of environment space.

Click the batch file instwin.bat or gap.bat which caused the problem with the right mouse button and select Properties,Memory and increase the initial environment space to at least 1024. This will create a pif shortcut which should be used to start GAP.

Command line editing does not work under Windows.

The default key commands are UNIX-like. GAP also tries to emulate some of the special keys under Windows, however if the key repeat is set too high, Windows loses parts of the codes for these keys and thus GAP cannot recognize them. Windows98 produces the same scan code for all cursor keys. As GAP does not interface directly with the Windows machinery, there is no way around this problem so far.

The ^-key cannot be entered.

This is a problem if you are running a keyboard driver for some non-english languages. These drivers catch the ^ character to produce the French accent-circonflexe and do not pass it properly to GAP.

Cut and Paste does not work

See http://www-gap.dcs.st-and.ac.uk/~gap/Info4/windows.html for a remedy.

If all these remedies fail or you encountered a bug please send a mail to gap-trouble@dcs.st-and.ac.uk. Please give the input which caused your problem and state the machine, operating system and version of GAP (for example ``gap4r2, fix1'') you are using.

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