Eric S Fraga <e.fraga@ucl.ac.uk> writes:

> in the paper I am writing, I have a number of gnuplot src blocks, some
> of which process a significant amount of data so take some time to
> generate the actual plots.  The data are static so caching the results
> make sense.  However, even though I have ":cache yes" on each of these
> named src blocks, and I have (for good measure), the property
> "header-args:gnuplot" set to ":cache yes" as well, the plots are being
> regenerated each time I export to PDF via LaTeX.

I was able to reproduce. The reason why caching does not work is related
to the way :var assignments work in ob-gnuplot. We dump the table data
into temporary files and refer to those files in generated gnuplot
script body. The temporary files names change on every execution and the
gnuplot script hash is never going to be the same.

I am attaching tentative patch to fix the issue.
The patch introduces a new functionality to ob-core.el allowing more
stable temporary file names. I am not sure if my implementation is the
best way to solve the problem, so comments are welcome.

Best,
Ihor