Re: [PATCH risu] use time() as random seed and introduce --randseed option

["Alex Bennée" <alex.bennee@linaro.org>]

Peter Maydell <peter.maydell@linaro.org> writes:

> On Fri, 5 May 2023 at 01:23, Jun Sun <jsun@junsun.net> wrote:
>>
>> Agree on the usefulness of generating the same test. That is the
>> reason behind adding --randseed option. Once a seed is set, it
>> always generates the same sequence of instructions.
>>
>> Basically with this patch,
>>
>> by default you will generate random instruction sequences for most testing cases
>> you can provide a random seed option in the commandline to generate a deterministic instruction sequence
>>
>> Without this patch,
>>
>> we always get one fixed sequence (ie. random seed == 0 case)
>> Otherwise we would have to manually modify code to generate random
>> instruction sequences or generate a different fixed sequence.
>>
>> Hope this clarifies things a little bit.
>
> Mmm; it comes down to: should we default to 'time' and
> require the user to specify --randseed 0 to get the old
> behaviour; or do we retain the current behaviour as the
> default and let the user pass an option if they want a
> non-reproducibly random output.
>
> Alex, what do you reckon? You probably have been using
> risugen more actively than me recently. I guess I vaguely
> lean to "default to randomize(time)".

I'm easy either way as long as we as long as we print out the seed so we
can deterministically regenerate if we want to.

>
> Also, should we make risugen print the random seed to stdout
> so you can repro it even if you didn't pass --randseed initially?
>
> Now that the random-seed-setting is 6 lines instead of 1,
> this should definitely be abstracted out to a function
> in the common code and not repeated in each per-arch file.
>
> thanks
> -- PMM


-- 
Alex Bennée
Virtualisation Tech Lead @ Linaro