Unlinking many clones as well as combining many objects takes a long time

[uellue]

I've compared the time it takes to unlink 100 clones and 2500 clones.
100: 1.5 s (ok)
2500: 250 s (too long)

Then I've combined the objects.
100: 1.5 s (ok)
2500: 178 s (too long)

And then I've created a pattern from the object.
100: ok
2500: pattern creation is fast, but afterwards the UI is extremely sluggish.

Note that the times do not scale linearly with the number of objects or nodes.

In detail, I've been working with tiled clones to make a pattern. I've ran into crashes as well <https://bugs.launchpad.net/inkscape/+bug/298248>. The pattern is supposed to be non-repeating, therefore the many clones.

I am using Inkscape 0.48.4 r9939 on Windows 7 Enterprise 64 bit.