[Liblas-devel] Performance hit from 1.21 to 1.6b3

[Howard Butler]

On Dec 17, 2010, at 11:23 AM, Howard Butler wrote:
> 
> One area of the code that I suspect is performance sensitive, but I haven't done a lot of profiling of, is the portions of liblas::Point that determine where in the point's byte array to fetch the dimension from.  Currently, for fixed-schema point formats, this is likely doing unnecessary work (the point formats are fixed and cannot change position).  I will look into that and see if my raw i/o timings match yours and if I can improve them in any way.  If you have call stacks or other profiling information, I would be excited to see what it might show.  Find me on IRC to discuss some more today if you're interested.

Hell yes, this was sensitive.  Instead of dynamically looking up the byte positions for interpreting data, I have hardcoded them (they don't change for the base PointFormat 0 ... 3), and here are the 5-run timing results.

> hardcodes
> 
>         0.37 real         0.24 user         0.07 sys
>         0.32 real         0.24 user         0.06 sys
>         0.32 real         0.24 user         0.06 sys
>         0.32 real         0.24 user         0.06 sys
>         0.32 real         0.24 user         0.06 sys
> 
> dynamic
> 
>         0.60 real         0.52 user         0.07 sys
>         0.60 real         0.52 user         0.07 sys
>         0.60 real         0.52 user         0.06 sys
>         0.60 real         0.52 user         0.07 sys
>         0.70 real         0.52 user         0.07 sys
> 

Howard