Re: [Visualpython-users] Visual 3.2.4

[Jonathan B. <jbr...@ea...>]

On Mon, 2005-12-19 at 18:48 -0500, Jeremy Sachs wrote:
> I'm working on a program that draws a continuous curve, and when the  
> number of points on that curve exceeds 1024, a new curve is drawn at  
> the end of the old curve.
> 
> How many 1024-point curves can visual python manage before crashing?

Here goes a long answer to a simple question...

It should go until you run out of physical RAM.  For N points, the
maximum memory usage is 2*3*sizeof(double)*2*N, or 48 bytes per point,
but it can be as few as 24 bytes per point.

Curve objects preallocate storage for up to 2x the total number of
points in order to make curve.append() work fast.  When using .append(),
the total allocated storage is approximated by min( 256, 2^X) for
incrementally increasing values of X (it is actually slightly more than
this).  If you precalculate the curve's pos or color array rather than
simply append() to it, the storage will be enough for exactly 2x the
size of the initial array (doubling as needed for subsequent appends).
You don't normally see this extra allocation since curve.pos is actually
a slice into the real pos array.

For your usage pattern, the extra space will be small, and total storage
will be a pinch larger than 24 bytes per point.  There's also some
per-object overhead which should be pretty small compared to the storage
required for the points themselves.  Therefore, per-object memory usage
should be about 24-25K per 1024-point curve segment.

As far as rendering goes, curves with zero radius (the default) are
rendered much much faster than thick curves.

HTH,
-Jonathan