Re: [matplotlib-devel] Re: Speed of dynamic_image

[Todd M. <jm...@st...>]

On Thu, 2004-07-15 at 10:25, John Hunter wrote:
> >>>>> "Gregory" == Gregory Lielens <gre...@ff...> writes:
> 
>     Gregory>   It seems thus that Agg drawing is the main limiting
>     Gregory> factor here, all the tricks to avoid using strings (or
>     Gregory> reallocating Agg renderer, for that matter) are not too
>     Gregory> usefull...  What I do not understand is why I got such
>     Gregory> low values, compared to the 4 or 10 FPS: I guess, given
>     Gregory> the impact of Agg drawing, all the *Agg backends should
>     Gregory> have about the same speed...Is there something I miss
>     Gregory> here?  My workstation is not current top of class, but
>     Gregory> it's a PIV 2.3 GHz, so certainly not slow either...I do
>     Gregory> not think the graphic subsystem is at fault, cause except
>     Gregory> for a mistake of my part, blit only test shows that Agg
>     Gregory> is really the origin of the poor FPS...
> 
> My best guess: your numerix settings don't agree. This will cause very
> poor performance, since the extension code has to fall back on the
> python sequence API (is this actually the correct explanation of why
> it's slow, Todd?)

I believe that's correct.  If matplotlib is compiled against Numeric,
the array API calls don't see arrays, they see sequences (numarrays)
which must be converted into (Numeric) arrays.  This adds both
constructor overhead and sequence protocol overhead (almost certainly
the dominant factor for all array sizes).

Regards,
Todd