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From kellen sunderland <kellen.sunderl...@gmail.com>
Subject Re: CUDA / CUDNN support revisited
Date Wed, 19 Jun 2019 16:56:41 GMT
I think where we're all going to have agreement is that we shouldn't have
code targeting CUDA versions earlier than CUDA 9, or cuDNN versions earlier
than 6.  We can go ahead and remove any code that targets those old
versions, and drop any SMs that are not supported by CUDA 9 / cuDNN 6.  Id
suggest we also add some logging for users with prior versions letting them
know they can still use MXNet 1.4.

Where things get interesting is CUDA 9 / cuDNN 6 support.  I was originally
a proponent of the N and N-1 route for simplicity.  Looking back at the
choice, one complication I see is that there's competing concerns between
semver library compatibility and feature releases on NVIDIA's part.  NVIDIA
is releasing new libraries with a lot of new features on a regular basis,
which is good, but for compatibility reasons they've begun to bump major
versions less often, which is also probably also good.  For example if
memory serves correctly cuDNN used to get an MV bump every 6 months or so,
but now the N-1 MV (6) was released in April of 2017.  As a project
maintainer I would certainly like to drop support for library versions that
are 2 years old in my latest release.  Supporting a 2 year wide range of
dependency libraries in the CI for example is going to be a burden.

>From the MXNet users' perspective obviously having to update dependencies
is a pain, but updating these libs are likely to give significant
performance increases (occasional perf regressions aside).  I think a
consistent thread I've heard from users is that training takes too long,
inference costs too much, and they want their DL framework to abstract the
complexity of using custom hardware like TCs or AVX with them having to put
in a lot of effort.  Another consideration is that using old versions of
MXNet is actually quite easy and convenient thanks to (IMO) some solid
release practices and naming conventions.

Given how easy it is to use old MXNet versions I think it's reasonable to
target CUDA 10 and cuDNN 7 only in release 1.5 (and drop incompatible sm
versions).

On Wed, Jun 19, 2019 at 4:01 AM Marco de Abreu <marco.g.abreu@gmail.com>
wrote:

> Good points anirudh. Generally I would understand N as being the major
> versions. Speak we would maintain CUDA 9 and 10.1 in your given example and
> drop 10.0 as soon as we verified that 10.1 is working. CUDA 9 would only be
> dropped when 11 is released and tested.
>
> At the same time, we would always only supported the latest compatible
> cudnn version. Or is there any reason somebody would use an old cudnn
> version?
>
> Wdyt?
>
> -Marco
>
> Anirudh Subramanian <anirudh2290@gmail.com> schrieb am Mi., 19. Juni 2019,
> 01:47:
>
> > +1, Agree this should be done for both CUDA and CUDNN versions. At max
> CUDA
> > Version N and CUDA Version N - 1 should be supported in CI.
> >
> > My question is what happens, when we are at a position, where we are on a
> > CUDA version N and removed support for CUDA version N - 1. Within a small
> > duration Nvidia comes up with a CUDA patch version N + 1, where  some
> perf
> > regressions and some bugs have been fixed. Should we just move to N + 1,
> > since version N will have all these issues for users and may also slow us
> > down on CI.
> >
> > I am facing a issue with CUDA 10 and CUDA 10.1 which also seems to be
> > causing intermittent CI failures:
> > https://github.com/apache/incubator-mxnet/issues/15273 . There is
> already
> > a
> > PR to bump up Nvidia version to 10.1 (
> > https://github.com/apache/incubator-mxnet/pull/14986/files).
> >
> > I think for situations where there is a quick follow up release like 10.1
> > and MXNet users are impacted by certain issues, we should just bump up
> the
> > version and stop support for 10.0.
> > Would like to hear more from Nvidia folks (on this particular case of
> CUDA
> > 10.0 vs CUDA 10.1 and what are the recommendations for existing
> customers).
> >
> > Anirudh
> >
> > On Mon, Jun 3, 2019 at 4:21 PM Dick Carter <dickjc123@apache.org> wrote:
> >
> > > Actually, I tried to say that support *doesn't necessarily* include
> N-1.
> > > I'm proposing that the supported versions are 1) covered by CI and 2)
> > have
> > > been available in a usable form long enough that a semi-motivated user
> > has
> > > been able to transition to it.  That might mean only N (e.g. per my
> > > proposal, only cuDNN v7).
> > >
> > > Regarding precedent for N / N-1,  when a new CUDA version comes out,
> > users
> > > will transition to it at their own pace, thereby creating a N / N-1
> > support
> > > situation for some period.
> > >
> > >
> > > On 2019/06/03 22:43:20, Pedro Larroy <pedro.larroy.lists@gmail.com>
> > > wrote:
> > > > Your proposal of having support for N and N-1 makes a lot of sense to
> > > > me. Are there use cases for supporting older CUDA versions?
> > > >
> > > >
> > > > Thanks.
> > > >
> > > > On Mon, Jun 3, 2019 at 3:06 PM Dick Carter <dickjc123@apache.org>
> > wrote:
> > > > >
> > > > > I'd like to revisit the discussion of:
> > >
> >
> https://lists.apache.org/thread.html/27b84e4fc0e0728f2e4ad8b6827d7f996635021a5a4d47b5d3f4dbfb@%3Cdev.mxnet.apache.org%3E
> > > now that a year has passed.
> > > > >
> > > > > My motivation is:
> > > > >
> > > > > 1.  There's a lot of hard-to-read  '#if CUDNN_MAJOR' code
> referencing
> > > cuDNN versions back as far as v4(!?).  We need to clean this out before
> > it
> > > hampers our ability to nimbly move the codebase forward.
> > > > >
> > > > > 2.  There seems to be a difference of opinion on whether we should
> be
> > > supporting version 'N-1' (e.g. cuDNN6).  Our current MXNet 1.5
> candidate
> > > does not compile against cuDNN v6, so this should be either fixed or be
> > > up-front stated to the user community.  The breaking PR was
> > > https://github.com/apache/incubator-mxnet/pull/14476.
> > > > >
> > > > > Having read the prior discussion, my take on it is:
> > > > >
> > > > > - Users should be given an ample time period (1 year?) to move to
a
> > > new CUDA/cuDNN version once it becomes 'usable.'
> > > > >
> > > > > - We should not claim to support a given version if it is no longer
> > > part of the MXNet CI.  User's should be warned of an impeding dropping
> of
> > > this 'testing support.'
> > > > >
> > > > > So these statements do not necessarily promise 'N-1' support.  I
> > could
> > > see a transitioning of the CI from CUDA9-only -> CUDA9&10 -> CUDA10
> only.
> > > Some period before CUDA9 is dropped from CI, the user community is
> > warned.
> > > After that time, CUDA10 might be the only version tested by CI, and
> hence
> > > the only version supported (until the next CUDA version came around).
> > > > >
> > > > > Let me propose as a 'strawman' that we claim to support CUDA
> version
> > 9
> > > and 10, with cuDNN version 7 only.  Those versions have been out for
> over
> > > 1.5 years.  So no CUDA 8 or cuDNN v6 support- over 1.5 years old with
> no
> > > coverage by our CI.
> > > > >
> > > > >     -Dick
> > > >
> > >
> >
>

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