> < ^ Date: Thu, 11 Nov 1999 17:21:38 GMT
> < ^ From: Willem de Graaf <degraaf@math.uu.nl >
^ Subject: bugfix #7

Dear Forum,

This is to announce bugfix number 7 for GAP 4.1. The priority of this fix
is high.

This fix fixes

1) a problem with randomness in 'DerivedSubgroup' and 'NormalClosure',
2) a problem with 'NaturalHomomorphismByNormalSubgroup',
3) a problem with the function for creating homomorphisms from
permutation groups via a factor group pcgs; this caused
some groups from the primitive groups library not to be transitive,
4) a problem with 'NumberFFVector'.

Errors 1) and 3) might produce wrong results.
Error 1) shows up when calculating with permutation groups of large degree
(>= 100 ).
Of Error 3) an example is included at the end of this mail.

With this fix, the primitive groups library now passes the checks of correct
degree, transitivity and primitivity.

Many thanks to:
Herbert Pahlings for reporting error 1),
Michael Leithold for reporting error 2),
Peter M"uller for reporting error 3)
Toshio Sumi for reporting error 4).

Before applying this fix it is necessary to have installed fixes 1, 2, 4, 5,
and 6 previously.

You do *not* have to recompile, and you do *not* have to get a new binary.

You should not apply this fix to any version of GAP3.

Load the zoo archive 'fix4r1n7.zoo' from the bugfixes web page
Alternatively you can find this file in the 'bugfixes' directory of the
GAP4 ftp distribution.

Unpack the file in the home directory of your GAP distribution (the
directory containing the 'lib' and 'src' directories) using 'unzoo -x
fix4r1n7.zoo'. 'unzoo' may ask you for permissions to overwrite files,
answer this with Y)es or A)ll. This will replace the erroneous file by
fixed version.

(On a PC or a Mac you will have to copy 'unzoo' in the same directory and
enter the argument line after the call to 'unzoo'.)
Make sure you have write permissions when applying the fix.

You can remove the file 'description7' afterwards.

After installing the bugfix you can test whether
the bugfix has been applied correctly by starting GAP from the 'gap4r1'
directory and issuing

gap> ReadTest("tst/bugfix.tst");
+ bugfixes test
+ GAP4stones: 835

(The output should be like this if the bugfixes have been installed
correctly. The number of GAP4stones may vary according to your system.)

Willem de Graaf, 11-Nov-99

# Example for error 3):
gap> g:=PrimitiveGroup(25,20);
gap> Size(g);
25                               # This should be 3000.
gap> IsTransitive(g,[1..25]);
false                            # This should be true.

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