Re: Parsing timestamps?

On Mon, 14 Jul 2025 7:50:04 +0000, Anton Ertl wrote:

mhx@iae.nl (mhx) writes:

On Mon, 14 Jul 2025 6:04:13 +0000, Anton Ertl wrote:

[..]

The question is: What properties do you want your computation to have?

[..]

2) A more accurate result?  How much more accuracy?
>
3) More performance?

3) + 2). If the result is more accurate, the condition number of
matrices should be better, resulting in less LU decomposition
iterations. However, solving the system matrix normally takes
less than 20% of the total runtime.
I've never seen *anybody* worry about the numerical accuracy of
final simulation results.
[..]

C) Perform tree addition
>
  a) Using 80-bit addition.  This will be faster than sequential
     addition because in many cases several additions can run in
     parallel.  It will also be quite accurate because it uses 80-bit
     addition, and because the addition chains are reduced to
     ld(length(vector)).

This looks very interesting. I can find Kahan and Neumaier, but
"tree addition" didn't turn up (There is a suspicious looking
reliability paper about the approach which surely is not what
you meant). Or is it pairwise addition what I should look for?

So, as you can see, depending on your objectives there may be more
attractive ways to add a vector than what you suggested.  Your
suggestion actually looks pretty unattractive, except if your
objectives are "ease of implementation" and "more accuracy than the
naive approach".

Sure, "ease of implementation" is high on my list too. Life is too
short.
Thank you for your wonderful and very useful suggestions.
-marcel
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