Re: with parallelaxes dumps core

[sfeam <sf...@us...>]

On Tuesday, 27 January 2015 03:06:16 AM Daniel J Sebald wrote:
> On 01/26/2015 10:38 PM, sfeam wrote:
> > On Monday, 26 January 2015 07:28:19 PM Philipp K. Janert wrote:
> >>
> >> The new plot style "with parallelaxes"
> >> is cute. Unfortunately, it also dumps
> >> core - whenever there are more than 7
> >> columns to plot.
> >
> > The maximum is set at compile time, but
> > yes the default is 7.
> >
> >> 1) This limitation is not mentioned in
> >> the doc. (As far as I can see.)
> >
> > I thought it was, but now I can't find it either.
> > That is an oversight.
> >
> >> 2) Dumping core unconditionally is not
> >> a good user experience. It would be
> >> better to detect and reject the illegal
> >> input and warn the user.
> >
> > Indeed.
> >
> >> 3) The limitation to 7 cols (which, I
> >> suspect, depends on limitations in the
> >> way "using" is parsed) puts the entire
> >> plot style into question. The whole
> >> point of parallelaxes plots (to the
> >> degree they HAVE a point) is to deal
> >> with high-dim data, easily exceeding 7.
> >
> > If you have such a use-case, go ahead and file a
> > feature request.  It should not be too hard to make
> > the axis structures dynamic rather than static.
> > The original request for this feature provided examples
> > from the literature but none of them had even as many
> > as 7 axes in a single plot.  So that seemed
> > adequate as a default.  Failing to check for more
> > columns of input than expected is purely a bug.
> 
> Here's the hunk of code from datafile.c that you are referring to:
> 
> 	    /* check we have room for at least 7 columns */
> 	    if (df_max_cols < 7)
> 		expand_df_column(7);
> 
> 	    df_no_cols = sscanf(line, df_format,
> 				&df_column[0].datum,
> 				&df_column[1].datum,
> 				&df_column[2].datum,
> 				&df_column[3].datum,
> 				&df_column[4].datum,
> 				&df_column[5].datum,
> 				&df_column[6].datum);


Not correct.
That code path applies _only_ to the command
   plot <foo> using 1:2:... "format-for-using-statement"
where an explicit format is provided.

> and I'm trying to recall how the internal storage of data points works. 
>   If I'm remembering correctly, there is some type of limitation on the 
> number of elements of a data point, e.g., x, y, x tolerance, y 
> tolerance, z (or color), etc. owing to the use of a structure to store 
> the data.  Was the size of the structure up to seven elements, therefore 
> it was generally thought that only up to seven columns of a data file 
> line would be used?  Is this parallel axes plot using the same limitation?

Not relevant.
The data for parallel axis plots is allocated dynamically,
one array per axis.

	Ethan