[Users] Vectorization issue

[Hee Il Kim]

Hi Erik,

I'm sorry for the late reply. I'm replying to ET as well to hear from
others about my short comments below.

On Thu, Jul 8, 2021 at 11:07 PM Erik Schnetter <schnetter at cct.lsu.edu>
wrote:

> Hee Il
>
> This looks disconcerting. Using vectorization or not should only
> affect things at the round-off level (the same way parallelization
> does).
>

I agree with you. But I'm not 100% sure myself whether I can ignore any
chance of dynamical instabilities owing to the round-off, even though it
would be extremely rare.


> The vectorization settings you show look good.
>
> I'd like to dig deeper.
>
> - Is your source code public, or would you be willing to share it with
> a few developers?
>

At least for this issue, I'm using public ET codes (mainly Turing version).


> - Is your parameter file public, or would you be willing to share it
> with a few developers?
>

Not public. I guess that this vectorization issue would be reproducible in
any circumstances if the resolutions are sufficiently high. For example,
the resolution used here is dxmin=0.25 num_levels=6, and dtfac=0.4. I can
share with you a public EOS version.


> - The first thing to do is probably to look at other, more fundamental
> variables (e.g. metric components) in 3d and see where they begin to
> differ. The hope is that they would begin to differ early during the
> run. Do you have such 3d output at the same time from both
> simulations? Or do you have 1d output e.g. along the x axis for some
> variables?
>

I can make you an account on my machine to access the data. I will let you
know if I gather the data.

Hee Il








>
> -erik
>
>
> On Thu, Jul 8, 2021 at 9:01 AM Hee Il Kim <heeilkim at gmail.com> wrote:
> >
> > Hi all,
> >
> > While examining different results from my colleague's, I found the
> vectorization option could develop misleading results. I seldom use the
> vectorization option but  in the configuration file but he mixed up with
> mine and others leaving:
> >
> > VECTORISE                = yes
> > VECTORISE_ALIGNED_ARRAYS = no
> > VECTORISE_INLINE         = yes
> >
> > in the config file. I found these are default config options in recent
> simfactory optionlists. Instead, I used to use AVX but always adding e.g.,
> "-fp-model precise" for value safeness.
> >
> > I attached two figures with the vectorization on/off. For the  case of
> no vectorization, I tested it w/wo AVX and got the identical result.
> >
> > Hee Il
> >
> > _______________________________________________
> > Users mailing list
> > Users at einsteintoolkit.org
> > http://lists.einsteintoolkit.org/mailman/listinfo/users
>
>
>
> --
> Erik Schnetter <schnetter at cct.lsu.edu>
> http://www.perimeterinstitute.ca/personal/eschnetter/
>
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