Re: [Pysdl-devel] slice operation, numpy, speed

[Peter N. <pn...@ya...>]

Ok I cut and pasted a lot here:

> Mark Baker writes:
> > right now in pysdl, there's no way to go mess with
> > pixels aside from the get_at and put_at. 
> This is inaccurate. You can manipulate surfaces
> using the slice operator.

So there is also the slice operator, but that turns
out even slower:

"David Clark <David Clark" <si...@te...> wrote:
> A note: in my testing, writing individual pixels by
> using the surface
> object's "list of lists" structure is about 25%
> slower than by using
> set_at() (as expected).

--- Pete Shinners <pe...@vi...> wrote:
> i've been spending time with Numeric, and it
> should be really simple to make some functions
> to transfer between surfaces and arrays. once
> this is done the fire demo should run swift 
> under python. (i would hope)

From the NumPy page - http://numpy.sourceforge.net/ :

>Why Numerical Python?
>If x and y are Numerical Python arrays, then the
>speed of the operation x + y is close to the speed of
>doing it in C if the arrays are big enough. Thus,
>Python can be extended with a full scientific array
>language with sophisticated indexing and shaping
>operations and yet be closer to the speed of a
>compiled language than to the speed of Python itself.


This is deep water for me but it seems like Pete
Shinners' idea of numpy-arrays that could be treated
as 'fake' software surfaces that could then use the
blit operation would be a decent solution to these
kinds of problems, if it can be done.  The
execute-buffer thing sounds like it would be better &
faster but also a lot more work to implement, though I
have no idea if this is true. Also I think it's really
important to keep things simple because that's the
whole reason to use Python instead of C anyway.

I doubt anyone is ever going to use PySDL for hardcore
mindblowing demo graphics, but it would be great to
have a reasonably easy way to implement simple effects
and not be totally limited to the sprite paradigm.
--Peter



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