with @ingox i discovered that big graphical data structures can take a very long time to close a patch (several minutes is possible, depending on the size and number) . there is a workaround, which is to clear the ds windows before closing the patch, i automated the process with a close button. but still its not a very nice way. does anybody know a better way or knows why it is that slow? is it perhaps faster with the 64bit version of pure data(which exists only for osx if i am right)? or do i have do accept that as a limit of the graphical data structures (it could be a problem of storage management)?

It's probably because of the line in glist_delete from g_graph.c that redraws all the scalars on every visible canvas when you delete any object like [drawpolygon] or [drawcurve].

Closing a patch triggers the deletion of every individual Pd object, including [drawpolygon], [drawcurve], etc. So for each one of those drawing instructions you have in your patch, Pd will send another message to redraw every single scalar.

@jancsika thanks very much, that could be the reason.