Re: [Flightgear-devel] Nasal property lookup performance

[Thorsten R. <tho...@sc...>]

> The above values are from accessing some 8000 properties, which would
> suggest that an individual property access from a props.nas Node
> reference costs something in the region of 6 microseconds on my
> machine (which amusingly wikipedia tells me is comparable to the time
> to execute one machine cycle on an Intel 80186 microprocessor or 1960s
> minicomputer!).

Please test this with different numbers than 8000 as well - I seem to see  
strange non-linear behavior in the time with time per property increasing  
with total number of properties to be written (which I'm a bit at a loss  
how to interprete).

> It's not clear to me whether using references from props.nas is
> therefore "fast enough" or whether there is value in trying to improve
> performance.

For well-organized code (aka writing only when needed, organizing the  
displays in suitable groups, staggered updates...), it's going to be fast  
enough. For a straightforward approach to complicated displays probably  
not.

A thousand properties sounds a lot, but every  update in translation is  
already 2 properties, combined with a visible flag and color information  
you're down to 166 elements you can update already.

If each of them is driven by reading a value from the tree you're losing  
even more.

Generally, if there is a way of making either method faster, it would  
affect performance in a positive way all over Nasal scripting because  
currently property I/O is in my view the largest bottleneck (especially of  
canvas).

* Thorsten