Adrien,

In the VUnit[1] test automation framework we are able to support multiple
parallel simulations using the same top level with different generic values
using --elab-run. We just ensure that different output folders are used.
This is possible thanks to some recent improvements in the output flags of
GHDL.

[1] https://github.com/LarsAsplund/vunit
Den 1 okt 2015 21:20 skrev "Adrien Prost-Boucle" <
[email protected]>:

> Hi Tristan,
>
> Now the -g options are implemented and work at run time, I tend to love
> it, and use it.
>
> I often design with large number of generics in order to be able to
> investigate impact on design efficiency / latency / throughput.
> I compile all VHDL files with the gcc version of GHDL, and obtain an
> executable.
> Then I launch many runs in parallel with different parameters (with -g
> options), and in different folders with different data files.
> This is extremely convenient.
>
> With -g options applying only at elaboration, I would have to do
> re-elaboration for each tested configuration.
> I suspect I would need to generate N versions of the simulator, in
> different directories, which could make GHDL usage more complicated.
> Elaboration take time (at least with the gcc version).
> Olof Kraigher suggested using --elab-run but measuring simulation time
> gets strongly biased this way.
>
> On one hand, I think being able to set some generics with -g at
> elaboration time can have a positive impact,
> on the generated simulator speed and on the generated executable size.
> But on the other hand, the disappearance of ALL generics for run time
> would be painful.
>
> But I haven't seriously investigated : what I wrote above is only
> assumption,
> please correct me if I'm wrong!
>
> The ideal flow would be, from my point of view:
> - all -g options set at elaboration time make the corresponding generic
> value be hard-set in the generated simulator,
> - -g options for remaining generics are still available at run time
> Such a flow would be very generic and this is guaranteed to fit any
> serious or fancy user need.
>
> Is -g support at run time really hard to maintain for current and future
> GHDL developments?
>
> Regards,
> Adrien
>
>
> On Thu, 2015-09-24 at 21:15 +0200, Tristan Gingold wrote:
> [...]
> > BTW, I plan to change the switch to override generics of
> > the top entity. It will still be -gNAME=VAl but have to be
> > set during elaboration.
> > This won't happen before 0.33.  I plan to have both
> > mechanisms for 0.34 but remove the current mechanism
> > for 0.35.  Let me know if this is an issue for you.
> >
> > Tristan.
>
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