Dear Forum, Dear Marc Keilberg, > I've been looking to sift through a particular family of a few ten-thousand > groups, which are not in any of the current libraries, to see if they have > certain properties. While it's relatively easy to construct the entire > family of groups via the anupq package, and the test I run on them is > relatively quick (a second or two per group on my computer), I run into > serious memory consumption issues when I go to start testing them all (with > a function specifically written to perform the test in question). While > the list of groups I want only takes up a few gigabytes, and each iteration > of the testing function should be consuming a small fraction of that before > it completes, my total memory consumption constantly ticks up as I run > through the list, ultimately consuming well more memory than the list of > groups itself.
There are tools (such as `AttributeValueNotSet` that aim to do this, but it is still possible that attributes that get called in the course of the calculation still get stored. What I have therefore done in such situations is to simply delete the whole group after having used it. This can happen in one of two ways (assuming L is your list of groups): a) You do not need the groups, only data obtained from them, or one counterexample: for i in [1..Length(L)] do G:=L[i]; # now do the test ... Unbind(L[i]); # so the group is gone as soon as the next iteration assignes G. od; A more subtle way (with keeping the list) is work on a new group G that is defined the same way (but is a different object. If you have permutation groups, you can do this as: G:=Group(GeneratorsOfGroup(L[i])); SetSize(G,Size(L[i])); # speeds things up if large but I suspect you have PcGroups. For these, it is probably best to make a *new* pc group with the same generators, so that there is nothing stored through attributes of the pcgs. That is, you use: G:=GroupByPcgs(Pcgs(L[i])); You will get a formally different group with same multiplication rules, and you can discard it once you are done. All the best, Alexander Hulpke
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