[vtkusers] Long-term support for previous VTK release

[Berk Geveci]

Hi David,

Sounds good. We had a discussion about testing at Kitware. With the new
infrastructure we have in place, we won't need nightly testing. We can just
test when changes are made to master. CDash now supports showing latest
dashboard results every day, no matter how long ago they were run. This
will allow us to throw as many dashboard systems as we use on the latest
version to older versions, since changes will happen rarely...

We need to figure out the details of how we will do this. It is likely VTK
8 and 9 will come fairly quickly after 7 and they are very likely to bring
fairly big changes both in terms of API as well as supported compilers. So
my current thinking is to have VTK 6 live for several years (3-5?) while 7,
8 and 9 would come and go fairly quickly. So anyone who doesn't want to
ride this new wave of changes could stick to 6 but those that jump on 7 or
later will have to be willing to move forward... Does this make sense?
Alternative suggestions are welcome. With the caveat that maintaining
multiple versions of several years would be challenging for the community.

Best,
-berk

On Wed, Jun 10, 2015 at 12:14 PM, David Gobbi <david.gobbi at gmail.com> wrote:

> Hi Berk,
>
> I'd love to see long-term support for older versions of VTK.  It could be
> done without placing any burden on anyone but the people who need it, if a
> couple simple rules are followed:
>
> 1) When we move to VTK 7, an LTS branch should be created for VTK 6, and
> this branch should remain open for X years.  Merge requests etc. for this
> branch should be handled exactly as for the master branch.  We could have a
> list of developers willing to review patches for this branch on the wiki
> (I'd certainly be willing to do so).
>
> 2) There should be no expectation of binary releases from an LTS branch,
> that would just create extra work for Kitware and would probably end up
> slowing down the whole process.
>
> 3) There would have to be a section of the dashboard available for each
> LTS branch for nightly testing at least.  Merges into the LTS branch should
> be rare enough that @home testing would be unnecessary.  I realize that
> this might entail some gitlab customization.
>
> I was not happy with how fast VTK 5 was dropped.  If there had been some
> way that I could have helped to support it, then I would have.
>
> Here in academia, it's very common for projects to be put on hold for two
> or three years due to temporary lack of funding, or because a lab goes for
> a couple years without a grad student who has the necessary expertise.  So
> if a grad student gets stuck with a project that requires a version of VTK
> that won't work on a modern system, it becomes very difficult to even get
> started.
>
>  - David
>
>
> On Wed, Jun 10, 2015 at 9:31 AM, Berk Geveci <berk.geveci at kitware.com>
> wrote:
>
>> Maybe one way of addressing this issue would be to keep two versions
>> maintained for a longer period? For example, we could commit to maintaining
>> (minor bug fixes and limited testing only) VTK 6 for 3 years after we
>> release VTK 7... That way customer that are stuck on old compiler can
>> benefit from bug fixes and testing longer. If they want newer features,
>> they would have to update. Given that we are likely to move to VTK 7 and
>> then 8 pretty quickly, even longer than 3 years may be warranted.
>>
>> I would argue for aiming for (mostly) C++ 11 by VTK 8, probably around
>> late 2016.
>>
>> -berk
>>
>
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