Re: [Gnash-dev] Performance drop [really trig functions]

[Jon Steinhart]

Eric wrote:
> I haven't delved at all into it in any depth, but when I looked at the 
> matrix code last month I did notice one thing I was going to recommend: 
> storing both canonical matrix parameters and the matrix itself and 
> computing the matrix only when necessary.  In other words, treating the 
> matrix values as a cache.  When matrix canonical values are assigned, all 
> the trigonometric function are recomputed, which is going to be the most 
> expensive operation of the lot.
> 
> Perhaps better: when assigning canonical values, check them against 
> existing canonical values.  If the same, do nothing.  If different, update 
> the value and invalidate the matrix values.  When performing a matrix 
> operation, check validity first and recompute if necessary.
> 
> In the same vein, caching the sine and cosine of the canonical rotation 
> value means that changing only the scale wouldn't incur any new 
> trigonometric computation.  In such a case the multiplications would dominate.
> 
> I don't know enough about how the matrix computations fit within the 
> overall control scheme of the player, but if they're in anything like an 
> inner loop, caching these calculations should significantly improve 
> performance.
> 
> Eric

My 2 cents on matrix computations; might want to have an option to use cordic
functions to do your trig on devices that don't have hardware for it.

Jon