Large project - planning calculation crashes

Hello,
I have a large project (+9800 activities) organized in several workstreams with interdenpencies. In reality there are less activities, but a lot of levels (indents).
The planning calculation does not finish. Either it times-out or crashes with the following error from Apache server log : PHP Fatal error:  Allowed memory size of 536870912 bytes exhausted (tried to allocate 118784 bytes) in Unknown on line 0 ...
I tried to "pause" 50% of the activities, but makes no change.
I investigated also to split the project in sub-projects, but then I cannot link (pred/succ) between them.
Is there a way to selectively use the planning calculator for example?
What are your suggestions?
Many thanks in advance for some advice. 

I was able to find the issue with this large project. There was a Circular Relationship. So the planning calculation was infinite and consuming memory and finally crashing. Now it takes about 10 seconds to do all the calculations. Maybe something to add to the consistency check feature in the administration tab.

The circular loop was between an activity and it's parent. I know it is controlled, but I cannot figure out how that happened.