POV-Ray : Newsgroups : povray.general : Need to run POVRAY on a single thread Server Time
29 Feb 2024 20:02:37 EST (-0500)
  Need to run POVRAY on a single thread (Message 1 to 5 of 5)  
From: Srihari
Subject: Need to run POVRAY on a single thread
Date: 8 Feb 2023 00:45:00
Message: <web.63e3357b503d41c895a6cf0b78dd8b08@news.povray.org>
Hi. I tried to run povray on a single thread and for the same purpose I used the
+WT1 option. I observed the following : (Refer image attached for reference)

While the photon time was shown with 4 threads used for processing the trace
time was shown with 1 thread. Searching a bit more, found that +WT option doesnt
control the photon time related threads. I then tried to change the gather
setting in GLOBAL_SETTINGS for photon with min_gather and max_gather set to 1
and tried to check maybe if this leads to only one thread getting used. But got
similar results( i.e 4 threads were displayed along with photon time).

How can we run the povray application completely on a single thread? Kindly
share your thoughts. Thanks


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povray_test.png


 

From: jr
Subject: Re: Need to run POVRAY on a single thread
Date: 8 Feb 2023 02:45:00
Message: <web.63e351e3b379c51b88a828ca6cde94f1@news.povray.org>
hi,

"Srihari" <sri### [at] yahoocom> wrote:
> Hi. I tried to run povray on a single thread and for the same purpose I used the
> +WT1 option. I observed the following : (Refer image attached for reference)

that, likely, is a misunderstanding.  you're telling POV-Ray to run with one
worker ("render") thread.  if you use the eg 'ps' command while POV-Ray runs,
you'll see a minimum of six active threads.


> How can we run the povray application completely on a single thread? Kindly
> share your thoughts. Thanks

if your scene code permits it, you could try and run POV-Ray version 3.6, which
aiui is the last version not "threaded".


regards, jr.


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From: Srihari
Subject: Re: Need to run POVRAY on a single thread
Date: 9 Feb 2023 01:50:00
Message: <web.63e49744b379c51b95a6cf0b78dd8b08@news.povray.org>
"jr" <cre### [at] gmailcom> wrote:
> hi,
>
> "Srihari" <sri### [at] yahoocom> wrote:
> > Hi. I tried to run povray on a single thread and for the same purpose I used the
> > +WT1 option. I observed the following : (Refer image attached for reference)
>
> that, likely, is a misunderstanding.  you're telling POV-Ray to run with one
> worker ("render") thread.  if you use the eg 'ps' command while POV-Ray runs,
> you'll see a minimum of six active threads.
>
>
> > How can we run the povray application completely on a single thread? Kindly
> > share your thoughts. Thanks
>
> if your scene code permits it, you could try and run POV-Ray version 3.6, which
> aiui is the last version not "threaded".
>
>
> regards, jr.

Thanks for the reply

Based on your inputs I tried to run with and without +WT1 option and check how
many no of threads of running

I could see that multiple threads were getting opened. But with +WT1 option one
thread was having like >12% CPU utilisation and others less than < 0.01.
Meanwhile with +I options I got two threads > 12% utilisation and others < 0.01

Assuming that the CPU threads refers to the trace time, is there any similar
ways to minimise number of threads or impact of threads on photon time and
radiosity time. Screenshots of CPU Utilisation are attached for reference


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with +wt1 option.png


 

From: jr
Subject: Re: Need to run POVRAY on a single thread
Date: 9 Feb 2023 03:05:00
Message: <web.63e4a84bb379c51b88a828ca6cde94f1@news.povray.org>
hi,

"Srihari" <sri### [at] yahoocom> wrote:
> ...
> Based on your inputs I tried to run with and without +WT1 option and check how
> many no of threads of running
>
> I could see that multiple threads were getting opened. But with +WT1 option one
> thread was having like >12% CPU utilisation and others less than < 0.01.
> Meanwhile with +I options I got two threads > 12% utilisation and others < 0.01

disclaimer - not an "expert" in things POV-Ray internals.  when you look at the
(text) output, you can see the various stages.  first parsing, that is always
one thread "working", next stage stuff I know little about like photons +
radiosity, but, as you observed, multiple threads involved.  last the actual
render, and you tell POV-Ray to use 'wt' threads at most to do that.  the
remaining threads are (the "main" thread aside) to service the console IO etc.

in a typical scene where more than just a test render is done, you'll see CPU
utilisation "at capacity" unless you use options; so eg for an old Core2 (== 4
h/ware threads), I see 397/398%, solid, until POV's done.


> Assuming that the CPU threads refers to the trace time, is there any similar
> ways to minimise number of threads or impact of threads on photon time and
> radiosity time. Screenshots of CPU Utilisation are attached for reference

not that I'm aware of, but hope someone in-the-know will butt in.


regards, jr.


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From: William F Pokorny
Subject: Re: Need to run POVRAY on a single thread
Date: 9 Feb 2023 07:06:28
Message: <63e4e1c4$1@news.povray.org>
On 2/9/23 03:01, jr wrote:
>> Assuming that the CPU threads refers to the trace time, is there any similar
>> ways to minimise number of threads or impact of threads on photon time and
>> radiosity time. Screenshots of CPU Utilisation are attached for reference

> not that I'm aware of, but hope someone in-the-know will butt in.

While making no claims to being in the know... ;-) My understanding 
matches yours jr.

I think the state of things is there is always more threads than +WTn 
active though often they are not consuming time. For example, there is a 
master thread sitting atop and managing the rendering threads - which 
consumes little time.

I'm not sure off the top of my head how the POV-Ray reported thread 
counts come about for photons and radiosity with respect to threads used 
and +WTn.

Bill P.


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