Octave problem started by calling drawnow().

[George Barrick]

Octave problem started by calling drawnow().

                                   2010.04.05.19:44:33 UT

Hello octave folks,

     I've begun to have a problem with my installation
of octave.  It is the pre-compiled octave-3.2.4 under
CygWin-1.7.3-1 on a WinXP Pro. SP3 uni-processor PC
(Dell OptiPlex GX260, 2.4 GHz, 1024 MBt RAM).  My
X-server is Xorg-1.7.6-2 with the XWin window manager.
This cygwin/octave uses gnuplot-4.2-4.

     I had been following the thread begun by
forkandwait on 2010.03.24 that started with the question:
"Gnuplot scripts as output?".  Several people who posted
on that thread mentioned an undocumented usage for the
drawnow() function in octave.  The gnuplot commands spun
up by octave interested me enough that I attempted the
function call mentioned in the e-mails.

drawnow("x11", "/dev/null", false, "gnuplotout.dat")

I ran the drawnow() command immediately after the finish
of my plot commands inside an m-file.  Octave issued the
error messages below, and returned to await my further
input.  I received no "gnuplotout.dat" file from the
octave program.

error: __gnuplot_get_var__: Can not open fifo.
error: called from:
error:   /usr/share/octave/3.2.4/m/plot/__gnuplot_get_var__.m
               at line 156, column 7
error:   /usr/share/octave/3.2.4/m/plot/__go_draw_axes__.m
               at line 39, column 18
error:   /usr/share/octave/3.2.4/m/plot/__go_draw_figure__.m
               at line 92, column 3
error:   /usr/share/octave/3.2.4/m/plot/gnuplot_drawnow.m
               at line 99, column 5

      Unfortunately, I now get this same difficulty with
octave at any instance where I call for a plotting window.
Specifically, it occurs _every_time_, even for simple scripts
like the following one:

<file: frst_plot.m>
xvals = [ -3.0 : 0.2 : 5.0 ]         ;
wuns  = ones( size( xvals ) )        ;
yvals = (-2.0)*xvals + (1.5)*wuns    ;
plot( xvals, yvals, 'k-' )           ;
</file>

I've tried all of the stupid things:

   close octave; restart

   close octave; close Xwin; restart

   close octave; close Xwin; shutdown PC; restart

   delete the file D:/cygwin/tmp/.X0-lock; restart Xwin

   delete the file D:/cygwin/tmp/.X11-unix/X0; restart Xwin

   delete files D:/cygwin/tmp/oct-22d***.0; restart octave

Every instance of octave now seems incapable of
communicating with gnuplot.

     My gnuplot can be run with no difficulties; it
successfully plots the parabola in the file below to a
new x11-window.

<file: parabs.gnu>
set title "Filled parabola" 0.000000,0.000000  font ""
plot 50-x*x with filledcurves
</file>

     The only thing that I have installed today is the
upgrade of the cygwin.dll.  It moved from 1.7.2-2 to
version 1.7.3-1.  This seems to be an octave problem
because gnuplot itself still performs well.

     I realize that this is (again) one of those
infuriating things that only the gbarrick could possibly
bring down upon himself.  Have I (stupidly) reset the
pipeline from octave to gnuplot so that it points to
/dev/null?  Can anyone suggest some tests that I could
perform to extract some more information about
the problem?


Thank you,

George                                  address@hidden

P.S.  Please forgive the length of this post.