making many plots quickly

[Francesco Potorti`]

Using the movie.m function that I posted some time ago (and that you can
find at <http://fly.isti.cnr.it/pub/software/octave/movie.m>) I can make
movies from a series of plots saved on disk as .png files.

The way it works is that I use for each frame
  figure("visible","off")
then I create the plot and save it as png with
  drawnow("png",sprintf("%6d.png",fileno++))
and at the end I call ffmpeg or whatever.

When making many plots (hundreds or thousands) I see that octave and
gnuplot take each 50% of CPU usage.  Looking ad drawnow.m, the cause
seems to be that when drawing a plot to a file the pipe to gnuplot is
closed each time.  If I could keep the pipe open, I could exploit having
a dual-core CPU to make things faster.  And probably I would also save
the CPU power needed to create and close a process for each frame.

Is there in Octave any way to use gnuplot like this?

If not, would it make sense for me to submit a patch that modifies
drawnow for general usage, so that it keeps the pipe open when possible?

-- 
Francesco Potortì (ricercatore)        Voice: +39 050 315 3058 (op.2111)
ISTI - Area della ricerca CNR          Fax:   +39 050 315 2040
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