OK. Thanks you. Found it.
In base to the code is feasible in a couple of weeks.
I-ll implement a second order kahan algorithm. Third order would be overkill ( I don't think anyone is gonna use it for high precision calculus ).
But it's not only sum and average, variance (stats) and any other formula with sums is affected. That's why I need time to track it.
And by the way, what about using long double for intermediate steps, to improve precision. For what I know glibc or whatever uses gcc on fedora uses it, or at least exp((double)10) returns the same as exp((long double)10.
El mié, 9 dic 2020 a las 23:00, Eike Rathke (<erack@xxxxxxxxxx>) escribió:
Hi,
On Wednesday, 2020-12-09 20:25:17 +0100, Dante Doménech wrote:
> Does anyone know where are implemented the calc formulas?
Regina already gave pointers. Ask if you need more.
> I'd like to check out if it uses the kahan algorithm, pairwise sum or
> something else.
Kahan is not used, but there's
https://bugs.documentfoundation.org/show_bug.cgi?id=137679
to implement it. I thought Roman would start on that but maybe
I misunderstood. So if you'd like to tackle that you're welcome.
The current approach is quite simple, it just remembers one value to add
that later.
Eike
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