[Users] Vectorization issue

Hee Il Kim heeilkim at gmail.com
Thu Jul 15 12:45:16 CDT 2021

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>

> 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_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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