pyopengl-users

[PyOpenGL-Users] numpy/Numeric vs. numarray with glDrawPixels

[Tim H. <hi...@re...>]

Hello All,
    I have written a small ap to output video coming from arrays of type =
'w' in numpy and type 'UInt16' in numarray.  I send the arrays to =
glDrawPixels using the tostring() method in both array libraries.  This =
is all running inside wxPython and the looping is occuring through calls =
from OnIdle.  In both cases, this works nicely, but interestingly, the =
framerate in the numarray version is 30 fps (the max allowed from the =
video frame source) while the exact same code using Numeric runs at 15 =
fps.  I find this strange because otherwise, I have found Numeric to be =
faster than numarray.  Does anyone have any idea why this might be =
happenning.  Is there a better way than tostring() to pass 2d arrays =
from Numeric to glDrawPixels.  I noticed a post on that a while back, =
but no follow up on a solution.

thanks,
tim

Re: [PyOpenGL-Users] numpy/Numeric vs. numarray with glDrawPixels

[Toon V. <Too...@UG...>]

Tim Hirzel wrote:
>  This
> is all running inside wxPython and the looping is occuring through calls
> from OnIdle.  In both cases, this works nicely, but interestingly, the
> framerate in the numarray version is 30 fps (the max allowed from the
> video frame source) while the exact same code using Numeric runs at 15
> fps.  I find this strange because otherwise, I have found Numeric to be
> faster than numarray.

Numarray is optimized for large array operations, while Numeric has a
smaller overhead when working with 'small' arrays. (e.g. rotation
matrices etc.)
From http://www.stsci.edu/resources/software_hardware/numarray:
"numarray is efficient for large arrays (>20,000 elements) but is slower
than Numeric for small arrays by a factor of 2 to 4."