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Re: [tdf-discuss] Cores and threads


Hi Pedro,

On Mon, 2013-04-01 at 06:48 -0700, Pedro wrote:
Why doesn't Calc (at least under Windows...) use all available cores and
threads to speed up operations?

        Primarily because threading is hard. Code that is not written to take
advantage of multiple processors is reasonably hard to convert to code
that is; it involves a lot of structural change. The good news is - that
that structural change is underway inside LibreOffice - Kohei is doing
some great work there as of recently. There are plenty of public
documents to read if you google for problems around threaded
programming.

Opening a heavy (200k lines x 26 cols) xlsx file takes 6 seconds in a Intel
Core i5 (2 cores, 4 threads) using MS Office 2010. I can see the first 3
threads briefly going up to 70% load and it's loaded.

        It is entirely possible that Excel can parse and import sheets
separately since they are in separate streams inside the DOCX file -
that is not an option open to LibreOffice & ODF which embeds them all in
the same XML stream; calculation in Excel is threaded too.

Using Calc 4.0.2 after waiting 5 minutes watching the first thread at over
85% load (and the fan whirring like crazy), I gave up waiting.

        That is almost certainly completely unrelated to any form of threading
issue, and down to the world's lamest selection of algorithms and
implementations as showcased in the calc core :-) again Kohei is working
hard on doing some larger changes here for LibreOffice 4.1.

        HTH,

                Michael.

-- 
michael.meeks@suse.com  <><, Pseudo Engineer, itinerant idiot


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