Re: run flags vs active intervals


Larry Gritz <l...@...>
 

On Feb 4, 2010, at 11:32 AM, Christopher Kulla wrote:

My interpretation of these results is that indices always win - unless
we have a single span.
Spans only beat indices if there are is a single large span of 1's, or a large batch that is almost all 1's. (That's most primary batches, but nothing else.)


It might be worth using indices but having an
"all_points_sequential" optimization for simple ops where the
indirection overhead would be noticeable (all the templated ops can
get this for free)
That may be a good compromise. I think indices are a clear winner in all other cases, so perhaps this will eliminate the overhead in the few cases that spans seem to win, and then we're golden.


By the way - I don't really understand how you got any runflag
sequences that started with 0. Did you always dump out "npoints" or
only "begin/end" ?
I dumped out "npoints" but for the index test, only loop on [begin,end), as we do in the real shadeops. So there is no penalty for strings of 0's on either end. So primary batches (or conditional modifications to primary batches) can start with 0. Non-conditional secondary batches always start with 1 (because of the way our renderer sends them to OSL).


--
Larry Gritz
l...@...

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