Fwd: [libreoffice-documentation] Multi-threading in Calc

[Drew Jensen]

Also - I read in a couple of places online that if you have OpenCL support
enabled then the CPU threading stops.

I can't test that to see if it is true because I can't seem to get OpenCL
to work on this Linux desktop.

Trying it on a Windows machine should answer that question.

On Thu, Apr 23, 2020 at 4:56 PM Drew Jensen <drewjensen.inbox at gmail.com>
wrote:

> To follow up on that.
>
> Using LO 6.4 & 7.0 pre-release build on Ubuntu. Recalculating one of the
> OpenCL test xls files just now.
>
> Starting up with a command line
> MAX_CONCURRENCY=0 ./soffice
> Does turn the CPU threading off.
>
> Restarting with a command line
> MAX_CONCURRENCY=4 ./soffice
> Turns it back on (for my AMD a5800 processor this will give me two
> threads, because while the CPU is called a 4 core processor and it does
> have 4 accumulators it only has 2 floatingpoint cores and this is the
> limiting factor it seems) with recalculation time for the workbook is ~2x
> faster.
>
>
> On Thu, Apr 23, 2020 at 1:48 PM Drew Jensen <drewjensen.inbox at gmail.com>
> wrote:
>
>> BTW I'm copying a paragraph from an email on a different list.
>>
>> "Also - if you set MAX_CONCURRENCY=16 - or somesuch (ie. twice your
>> number of threads) - you may be able to defeat the hyper-threaded
>> halving, and see if this workload happens to be one that does better
>> with hyper-threading than without."M.M.
>>
>> It might be worth mentioning the MAX_CURRENCY setting for controlling CPU
>> thread usage.
>>
>> Also, I wonder if the folks answering could answer one other question:
>> Does LibreOffice OnLine also use cpu threading in the same way it does
>> when run for desktop or headless? It would be with noting in the
>> documentation if it does not, IMO.
>>
>>
>>
>> On Thu, Apr 23, 2020 at 9:56 AM Stephen Fanning <
>> stevemfanning.wh at gmail.com> wrote:
>>
>>> Mike and  Luboš,
>>>
>>> Many thanks for your help on this topic.
>>>
>>> Regards,
>>>
>>> Steve
>>>
>>> On Thu, 23 Apr 2020 at 11:16, Mike Kaganski <mikekaganski at hotmail.com>
>>> wrote:
>>>
>>>> On 23.04.2020 13:12, Luboš Luňák wrote:
>>>> > On Thursday 23 of April 2020, Stephen Fanning wrote:
>>>> >> As for the processing itself, I remain unclear about how Calc
>>>> allocates
>>>> >> tasks to threads. Can we give the user any general advice on how he
>>>> could
>>>> >> structure his spreadsheet to gain the maximum performance benefits
>>>> from the
>>>> >> availability of multiple cores? Or maybe there are ways to organise a
>>>> >> spreadsheet that will frustrate Calc's attempts to multi-thread,
>>>> which we
>>>> >> ought to advise against?
>>>> >
>>>> >  Technically threads are generally used only for formula groups,
>>>> which are a
>>>> > sufficient number of adjacent cells in a column that use the same
>>>> formula
>>>> > (and get different results because of relative cell addressing). In
>>>> UI terms,
>>>> > write e.g. "=A1*2" to B1, grab the bottom-right corner of the cell
>>>> and extend
>>>> > down. But it's implementated this way because that's usually how
>>>> large
>>>> > spreadsheets are created. So I think it's a needless complication to
>>>> be
>>>> > specific about this.
>>>> >
>>>>
>>>> IMO it's still useful to mention that the optimization is column-based.
>>>> Because many people don't realize that row-based layout is potentially
>>>> less efficient. This would be beneficial to those who don't create
>>>> spreadsheets according to how it's "usually" done.
>>>>
>>>> --
>>>> Best regards,
>>>> Mike Kaganski
>>>>
>>> _______________________________________________
>>> LibreOffice mailing list
>>> LibreOffice at lists.freedesktop.org
>>> https://lists.freedesktop.org/mailman/listinfo/libreoffice
>>>
>>
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