[GAP Forum] StructureDescription
aeb at win.tue.nl
Tue Jul 8 08:49:43 BST 2008
> 2. A slightly modified version of the program works substantially
> faster and with less memory; it's my understanding it will be in
> the next version of gap. (Thanks Burkhard!)
Where is it?
> 3. Crashing: ...
(I described not the "Segmentation fault" type of crash, but the
"recursion depth exceeded" / "memory exceeded" / "Holt/Plesken incomplete"
types of failure.)
> 4. Which group(s) of order 1024? I'd be intersted in seeing if the
> new version of StructureDescription can handle them.
Easier if you provide that new version. This happens in real life,
not a group from some library.
>> The GAP manual advertises:
>> "The method for StructureDescription exhibits the structure of
>> the given group to some extend using the strategy outlined below.
>> The idea is to return a possibly short string which gives some insight
>> in the structure of the considered group and can be computed
>> reasonably quickly."
>> (manual typo: s/extend/extent/)
>> It seems to me that the idea fails. Maybe it is meant to be used only
>> on baby groups, say with fewer than 100 elements, but used on
>> rather small groups it usually crashes after many hours.
>> Reactions are: recursion depth overflow (at recursion depth 5000), or
>> memory overflow (needs more than the 3GB allowed on the command line),
>> or missing info in Holt/Plesken library.
>> Other functions reveal the structure of the groups involved
>> rather quickly. I wonder what StructureDescription tries to do
>> that is so extremely expensive.
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