Re: strange multiplot behavior with wxt

[Ethan A M. <me...@uw...>]

On Wednesday, 28 June 2023 05:50:15 PDT Allin Cottrell wrote:
> I'm puzzled by a multiplot example where the output seems to be 
> non-deterministic -- though the fault may be in my script 
> (strange_multi.plt, attached).
> 
> I'm on Linux, using gnuplot 5.4.3 and also 5.4.8, using 
> the wxt terminal for screen display with the command line
> 
> gnuplot strange_multi.plt -persist

I have kept source and executables around for many versions of gnuplot.
I can reproduce your "missing bars in first plot" symptom with old
executables for 5.4.0 through 5.4.6, but not with 5.4.8 or the
development branch.  Any given executable seems to be 100% reproducible
in either failing or succeeding.

But here's the thing - if I rebuild 5.4.3 from the same original
source, I get a new executable that does not exhibit the problem.
So my suspicion is that the difference is the version of the 
wx- shared libraries the binary is linked against.

old gnuplot_5.4.3 binary (built May 2022)
 [~/temp] ldd /usr/local/bin/gnuplot_5.4.3 | grep wx
        libwx_gtk3u_xrc-3.1.so.5 => /lib64/libwx_gtk3u_xrc-3.1.so.5 (0x00007fc634b09000)
        libwx_gtk3u_html-3.1.so.5 => /lib64/libwx_gtk3u_html-3.1.so.5 (0x00007fc634a25000)
        libwx_gtk3u_qa-3.1.so.5 => /lib64/libwx_gtk3u_qa-3.1.so.5 (0x00007fc6349f6000)
        libwx_gtk3u_core-3.1.so.5 => /lib64/libwx_gtk3u_core-3.1.so.5 (0x00007fc634000000)
        libwx_baseu_xml-3.1.so.5 => /lib64/libwx_baseu_xml-3.1.so.5 (0x00007fc6349e2000)
        libwx_baseu_net-3.1.so.5 => /lib64/libwx_baseu_net-3.1.so.5 (0x00007fc63497f000)
        libwx_baseu-3.1.so.5 => /lib64/libwx_baseu-3.1.so.5 (0x00007fc633c00000)

new gnuplot_5.4.3 binary (built today)
[~/temp] ldd ~/cvs/gnuplot-5.4.3/src/gnuplot | grep wx
        libwx_gtk3u_xrc-3.2.so.0 => /lib64/libwx_gtk3u_xrc-3.2.so.0 (0x00007f3cedc64000)
        libwx_gtk3u_html-3.2.so.0 => /lib64/libwx_gtk3u_html-3.2.so.0 (0x00007f3cedb83000)
        libwx_gtk3u_qa-3.2.so.0 => /lib64/libwx_gtk3u_qa-3.2.so.0 (0x00007f3cedb54000)
        libwx_gtk3u_core-3.2.so.0 => /lib64/libwx_gtk3u_core-3.2.so.0 (0x00007f3ced200000)
        libwx_baseu_xml-3.2.so.0 => /lib64/libwx_baseu_xml-3.2.so.0 (0x00007f3cedb42000)
        libwx_baseu_net-3.2.so.0 => /lib64/libwx_baseu_net-3.2.so.0 (0x00007f3cedade000)
        libwx_baseu-3.2.so.0 => /lib64/libwx_baseu-3.2.so.0 (0x00007f3cece00000)

But it's only a suspicion.  It could instead be a difference in some
other set of libraries, or in the compiler version used.  Or it could be
a timing issue that either is or is not triggered by generated code.
Perhaps the generated code for your semi-reproducible case hits right
on the edge of that timing. 
In any case I don't think the difference indicates a change in the gnuplot
source code.

Having said all that, if someone pins down the actual point of failure
or timing issue, perhaps we could code around it.   

	Ethan

> On some invocations the frequency bars appear in the first sub-plot, 
> on other invocations they do not appear, the upper plot shows no 
> data. But if I write the plot to file using, say, pngcairo or 
> pdfcairo, the first sub-plot is always OK.
> 
> Am I misusing multiplot or might there be a bug here?
> 
>