Hi Astron,
On 12/07/2012 06:41 PM, Stefan Knorr wrote:
Hi Markus,
Since 4.0 we are able to use the cached values written into OOXML
files to prevent a slow recalculation when opening a file. Hoewever
Excel and Calc don't always give the same result for formulas so we
(Eike, Kohei and me) agreed that we need to give the user a choice
wether to recalculate the formulas or not.
How are users supposed to know when they need it and when they don't?
They aren't. Heck even we the Calc developers don't know that for sure.
Ideally all formula functions generate identical results. In the real
world, however, they generate slightly different results due to many
factors; different algorithms used internally, binary double precision
numbers rounding errors, and even some bugs in the formula function
implementations (either in Calc or in Excel). And this is always a
moving target as Calc and Excel both change the internal implementation
of formula functions between releases.
I'd assume that if users are supposed to work with the spreadsheet in
LibO, they need to use the numbers that LibO generates ...
It's actually a little more gray than that. I would expect the results
to be pretty close enough between Excel and Calc, so in most casual use
cases it shouldn't be necessary to recalculate on load every single
time. This is why we've decided to cache the results to speed up the
load time.
But in some advanced use cases where numerical precision and
tractability of the formula results is absolutely essential, this may
not be good enough, hence the need to provide a choice to the user.
thus, what
would sound more sensible to me would be an automatic blacklisting of
certain formulas whose results you know to be different in LibO than in
MSO (and then recalculate everything that depends on these, of course).
I'm afraid we can't do that with reasonable effort, especially when the
algorithm that Excel uses is not very well defined (and is potentially a
moving target). Even if we decide to do it, the data may not be
reliable enough to be usable, especially over a long haul.
Best,
Kohei
--
Kohei Yoshida, LibreOffice hacker, Calc
_______________________________________________
Libreoffice-ux-advise mailing list
Libreoffice-ux-advise@lists.freedesktop.org
http://lists.freedesktop.org/mailman/listinfo/libreoffice-ux-advise
