E pur si muove

Deep or shallow frame stack?

Wednesday, July 13, 2005

So I'm working on parsing the file created by hotshot. The question in the title relates to how the storing of the cumulative time has to happen. The problem is that every frame has to add it's time to the cumulative time of all the anchestors.

Shallow frame stack

Here it is feasable to just look up the name of every ancestor and then go and add the time to the cumulative time of every anchestor.

Deep frame stack

When doing the same as decribed above this will get very expensive. So I came up with an alternative. The plan is to keep a second stack with just the cumulative times. When a frame gets entered it adds the time delta (time since profiler callback was called last) to the time of it's parent and to the cumulative time of the parent in the separate stack

Now when a frame exits it add's its time delta to it's own time and to the top of the cumulative time stack (it's own cumtime). Then it adds this value (from the top of the cumulative time stack) to the parent (second to last position on the stack) and to it's own (real) cumulative time after wich it pops the cumulative time stack.

That's what I've just been implementing now. So the rest of today will be spent trying this out, writing unit tests for it and debugging it. Maybe I'll be able to start handling the line events too today. But that probably won't be tested till tomorrow.

Wednesday, July 13, 2005 |


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