Le 22/09/2015 12:09, scott a écrit :
>> Interesting. Perhaps you have a newer version of Process Explorer? Or
>> maybe there's some setting somewhere to configure this that I haven't
>> noticed...
>
> v16.05 here, can't see any relevant setting.
>
> If I tell POV to render with 6 threads I only get 50% usage, but with 12
> threads I get 100% usage.
>
> However the elapsed times for the benchmark are:
> 6 threads  : 192s
> 12 threads : 136s
>
> So 50% CPU is actually more like 70% CPU, but I guess it depends on the
> exact algorithm (how nicely it can hyperthread).
>
 From my personal bench with povray, a HT-core is worth between 20 to 
25% of a real core. (tests done on i7 980X, at nominal speed, with 
benchmark scene)

If the OS is not total crap, the threads are allocated first on distinct 
real cores.

beware, when comparing with time, the performance is 1/time.

your 6 threads has a performance index of 5.20833, about 0.868 per thread
your 12 threads has one of 7.35, about .613 per threads.
(and if you remove the 5.208 from the 7.35, the additional HT-core only 
provides 2.142, that's 0.357 per HT-core, so a HT-core thread is in your 
system about 41% of a real core thread, for povray-binary and your scene).

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>  From my personal bench with povray, a HT-core is worth between 20 to
> 25% of a real core. (tests done on i7 980X, at nominal speed, with
> benchmark scene)

This is on Win 7 with the standard POV binary, the benchmark scene and a 
Xeon E5-1650 @ nominal speed.

> beware, when comparing with time, the performance is 1/time.
>
> your 6 threads has a performance index of 5.20833, about 0.868 per thread
> your 12 threads has one of 7.35, about .613 per threads.
> (and if you remove the 5.208 from the 7.35, the additional HT-core only
> provides 2.142, that's 0.357 per HT-core, so a HT-core thread is in your
> system about 41% of a real core thread, for povray-binary and your scene).

Yes, I think the additional HT'd threads being worth 41% of a real core 
thread, is the same thing as saying that if you only use the real cores 
you're utilising about 70% of the total CPU performance available. I 
assume that modern compilers optimise code to be hyperthread nicely?

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Am 22.09.2015 um 15:06 schrieb scott:

> Yes, I think the additional HT'd threads being worth 41% of a real core
> thread, is the same thing as saying that if you only use the real cores
> you're utilising about 70% of the total CPU performance available. I
> assume that modern compilers optimise code to be hyperthread nicely?

Most unlikely - there's nothing much to optimize there.

In a hyperthreaded CPU, you actually /do/ have the number of cores that
the task manager claims you have, but they're not independent; instead,
they are organized in pairs that share various resources; for instance,
there might only be one floating-point arithmetics unit for each pair of
cores.

Any thread that needs any such shared resource /will/ compete for it
with any other thread running on the pair's other core. And as you
typically can't optimize away such resource requirements, you can't
optimize away the competition. In addition, different CPU types might
share different resources among core pairs, so you don't even know what
resources to try to avoid.

There might be ways for an application developer to optimize an
application for hyperthreading; the strategy would be to separate the
application's workload into two groups of threads that use different
sets of CPU resources, and coax the OS to run one thread from each group
in each pair of HT cores; this way, competition for resources will be
reduced. However, it might not be easy to partition the workload in such
a manner.

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On 22/09/2015 11:09 AM, scott wrote:
>> Interesting. Perhaps you have a newer version of Process Explorer? Or
>> maybe there's some setting somewhere to configure this that I haven't
>> noticed...
>
> v16.05 here, can't see any relevant setting.
>
> If I tell POV to render with 6 threads I only get 50% usage, but with 12
> threads I get 100% usage.
>
> However the elapsed times for the benchmark are:
> 6 threads : 192s
> 12 threads : 136s
>
> So 50% CPU is actually more like 70% CPU, but I guess it depends on the
> exact algorithm (how nicely it can hyperthread).

Oh, I see. I'm still running the single-threaded POV-Ray binary. So if 
it uses 1 core, it says 12.5% CPU. I thought you were saying your copy 
says 100% for each CPU core used. ;-)

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> Oh, I see. I'm still running the single-threaded POV-Ray binary.

Now why doesn't that surprise me? :-)

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On 9/23/2015 7:36 AM, scott wrote:
>> Oh, I see. I'm still running the single-threaded POV-Ray binary.
>
> Now why doesn't that surprise me? :-)
>
>
It surprised me. Ver 3.7 is shiny.


-- 

Regards
     Stephen

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Am 22.09.2015 um 22:58 schrieb Orchid Win7 v1:

> Oh, I see. I'm still running the single-threaded POV-Ray binary. So if
> it uses 1 core, it says 12.5% CPU. I thought you were saying your copy
> says 100% for each CPU core used. ;-)

Okay, now is officially the time for you to upgrade to POV-Ray 3.7. If
you refuse to, I /will/ consider that as a personal insult.

I've put a lot of effort into that version to make it awesome. You don't
need to try UberPOV (which is even more awesome), but you absolutely
/must/ install version 3.7. Now. No excuses.


(And yes, I /am/ at least semi-serious about the personal insult thing.)

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On 23/09/2015 08:04 AM, Stephen wrote:
> On 9/23/2015 7:36 AM, scott wrote:
>>> Oh, I see. I'm still running the single-threaded POV-Ray binary.
>>
>> Now why doesn't that surprise me? :-)
>>
>>
> It surprised me. Ver 3.7 is shiny.

I remember it being in beta for a long time, and having lots of 
interesting-sounding stuff. I wasn't aware it had actually made it to 
release version yet.

Then again, when was the last time I did much with POV-Ray? Sure, it's 
running 24x7 working on an animation, but I wrote that years ago. I 
haven't really "used" it much recently...

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On 9/23/2015 5:56 PM, Orchid Win7 v1 wrote:
> On 23/09/2015 08:04 AM, Stephen wrote:
>> On 9/23/2015 7:36 AM, scott wrote:
>>>> Oh, I see. I'm still running the single-threaded POV-Ray binary.
>>>
>>> Now why doesn't that surprise me? :-)
>>>
>>>
>> It surprised me. Ver 3.7 is shiny.
>
> I remember it being in beta for a long time, and having lots of
> interesting-sounding stuff. I wasn't aware it had actually made it to
> release version yet.
>
> Then again, when was the last time I did much with POV-Ray? Sure, it's
> running 24x7 working on an animation, but I wrote that years ago. I
> haven't really "used" it much recently...

An animation! I would get the latest version just for the speed up.

You've mentioned this animation before. Refresh my memory, if you would?

-- 

Regards
     Stephen

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On 23/09/2015 06:03 PM, Stephen wrote:
> On 9/23/2015 5:56 PM, Orchid Win7 v1 wrote:
>> Then again, when was the last time I did much with POV-Ray? Sure, it's
>> running 24x7 working on an animation, but I wrote that years ago. I
>> haven't really "used" it much recently...
>
> An animation! I would get the latest version just for the speed up.
>
> You've mentioned this animation before. Refresh my memory, if you would?

https://www.youtube.com/watch?v=8s7I80H96CM

That took about 2 years to render. I'm currently rendering the sequel, 
which is a similar thing inside a Cornell box.

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