[petsc-dev] speeding up testing by not always downloading external packages?

[Satish Balay]

Well I don't think the download time is significant [for all the
builds at ANL] - as compared to the build times.

For ex: most of the time - petsc-pkg-hash gets reused [and this saves
on both downloads and builds] - such builds take about 2h. But when
packages have to be rebuilt - it can take 2:45 to 3h [so download part
must be pretty small]

But yeah - its wasted bandwidth - and not tolerant to network
disruptions.

And the other issue: might help with CI on low-bandwidth locations
[say run a CI instance at my house on a spare laptop]

But yes - this requires infrastructure. The way I look at it is - we
need a "local mirror" or "cache" infrastructure. 

i.e keep the cache part separate from the build part [and not intertwine them]

Spack does stuff in this direction [and also has remote cache as one
of the 100 remote sites from where the packages can downloaded can be
down - but its not tolerant to certain changes - so I have to
periodically clean it - to have confidence in my build].


Note: If there is a git repo locally cached (and mirrored) - we don't
have to deal with shallow clones.

Might have a bigger impact if we can improve petsc-pkg-hash
infrastructure to avoid rebuilds in more cases. [i.e make it more
tolerant to configure changes - but its not clear to me - which
changes wont require rebuilds]

Satish


On Sun, 11 Oct 2020, Barry Smith wrote:

> 
>   Satish,
> 
>    Do you think the time to download all the external packages for each job is significant?
> 
>    Would using super shallow clones on the external packages help much in time? Maybe we should to them anyways to stop wasting bandwidth?
>    Currently we do full clones? but we don't need the huge histories. 
> 
>    A much more elaborate way to save more time
> 
>      On each test machine have repositories of all the external packages
> 
>      For each job, 
> 
>          do pull in all these repositories from remote that job depends on (usually this will get nothing so take no time)
> 
>         For each package either
>     
>             - build in a unique build directory of the repository directory directly (for CMAKE and packages that support out of base directory builds)
> 
>             - make a local shallow clone of the local copy of the repository to externalpackages for the rest and do those builds there 
> 
>        The average cost of this will just some shallow local clones instead of copying over from remote machines. 
>        The PETSc test directories can still be completely   cleaned out for each job so Satish need not worry about testing with dirty directories.
> 
>        This requires a bit of infrastructure, if it saves a minute it is not worth it, but if it cuts the pipeline time from 180 minutes to 150 maybe? 
>        Probably not worth it. Could also be done just for a couple of the most external package intense jobs.
> 
>   Barry
> 
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