hi,
I have to run benchmarks on a linux system ( suse 10.1 ) with a dual-core
processor ( Intel Core Duo 1.6 GHz ). I am currently using PovRay 3.7
beta14. how can I activate my second core? is there any parameter which i
can add to the command line << povray -benchmark >> ? thanks for your help!
scouti

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> beta14. how can I activate my second core?

	There is no need to "activate" your second code.  By default POV-Ray 3.7
will use 2 render threads, which means both of your cores should be used at
nearly 100% for rendering (if nothing else is taking up cpu power).  You might
check this using the 'top' command.

is there any parameter which i
> can add to the command line

	There is a new command-line option +wtN (N an integer) to set the number
of "work threads" (number of threads used for rendering).  Increasing this
number from 2 (the default, as mentioned above) might increase or decrease
the rendering speed depending on many factors.

	- NC

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Nicolas Calimet <pov### [at] freefr> wrote:
> By default POV-Ray 3.7
> will use 2 render threads

  Please cite the source where you got this info.

  As far as I know, the official behaviour is to use 2*cores threads.

-- 
                                                          - Warp

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:D

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thanks very much for your help!

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Warp wrote:
> Nicolas Calimet <pov### [at] freefr> wrote:
>> By default POV-Ray 3.7
>> will use 2 render threads
> 
>   Please cite the source where you got this info.
> 
>   As far as I know, the official behaviour is to use 2*cores threads.

Not on Unix as there is no fully portable way to determine the number of CPU
(cores). Only on Windows and Mac OS the number can be determined in a
unified manner. Every Unix uses its own way to do it, i.e. there is no
standard Posix way of getting this information that works everywhere.

	Thorsten

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Thorsten Froehlich <tho### [at] trfde> wrote:
> Not on Unix as there is no fully portable way to determine the number of CPU

  Ah, that explains it. I didn't know there was such a difference between
the windows and the linux versions.

> Every Unix uses its own way to do it, i.e. there is no
> standard Posix way of getting this information that works everywhere.

  OTOH, I'm pretty sure it would be possible to retrieve this information
in linux. Perhaps some "#ifdef LINUX" code could be added for this?

-- 
                                                          - Warp

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Nicolas Calimet <pov### [at] freefr> wrote:
> > beta14. how can I activate my second core?

> will use 2 render threads, which means both of your cores should be used at
> nearly 100% for rendering (if nothing else is taking up cpu power).  You might

How should this possible ?


A normal user have only a limited bandwith of CPU-power and this is far
away from 100% CPU power. Because a program/user wich gets realy 100% of
the  CPU power would block the computer for all other programs/users.
And this can not be allowed in a Multiuser-System.
(btw. web-severs handles this in the same way, by a bandwith-control).

So the "top" command shows only the capacity of the User-Bandwith....not
the absolute CPU usage.


You can verify this very simple. Go to the "root-mode" and start
provray with the highest possible "nice value" of the privileged mode.
In this mode povray gets *much more* CPU-power than a normal user can
ever get....this reduce on the one hand the Rendering-time,
on the other hand, it is nearly impossible to do any other things
one this computer during the render-time.

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On Mon, 14 Aug 2006 01:26:29 -0400, Meothuru wrote:

> Go to the "root-mode" and start
> provray with the highest possible "nice value" of the privileged mode.
> In this mode povray gets *much more* CPU-power than a normal user can
> ever get

Actually, you can renice user processes so they run at the highest
possible level; the behaviour in Linux is that a non-root user can set the
niceness level to a higher value than it's currently set.

There also can be a tradeoff if the processes impacted by running a
program at the highest priority affect processes that control disk i/o and
such - you can actually lose performance, depending on the process
(probably not so much the case with POV-Ray, but with things like bulkload
of a local LDAP server, the bottleneck tends to be the I/O channels rather
than processing, so pushing the niceness level to an 'unfriendly' level
can actually degrade overall performance of the bulkload).

Jim

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> So the "top" command shows only the capacity of the User-Bandwith....not
> the absolute CPU usage.

	IIRC the 'top' utility reads the /proc filesystem: it should thus give the
exact same stats whether you are root or a non-privileged user.  (Otherwise, top
would be able to report only the current user's jobs, not all jobs.)
	So I guess your claim is not true.  I'd appreciate if you have pointers
to prove me wrong.

> You can verify this very simple. Go to the "root-mode" and start
> provray with the highest possible "nice value" of the privileged mode.
> In this mode povray gets *much more* CPU-power than a normal user can
> ever get....

	Could you please backup this second claim with numbers?

	On my monocore machine (AMD Athlon XP), running POV-Ray 3.6.1(a) or 3.7.0.beta.14(b)
as root on a few scenes(c) with either default scheduling priority (nice 0) or highest
priority (-20) and no other cpu-demanding job running, I hardly get one second
speedup.

	So with those limited tests I do *not* observe what you claim above.

	- NC


(a) unofficial build prepared with icc 8.1.
(b) the binary is compiled with icc 9.1; tested using 1 or 2 render threads, see
below.
(c) scenes/advanced/mediasky.pov and grenadine.pov; more are being tested, but the
result
should not depend on the scenes nor the binaries.

===== mediasky.pov

*** 3.7.0.beta14

2 threads,   0:  115.803u 0.012s 1:56.13 99.7%   0+0k 0+0io 0pf+0w
2 threads, -20:  115.091u 0.028s 1:55.36 99.7%   0+0k 0+0io 0pf+0w

1 thread,    0:  115.703u 0.000s 1:56.03 99.7%   0+0k 0+0io 0pf+0w
1 thread,  -20:  115.107u 0.004s 1:55.34 99.7%   0+0k 0+0io 0pf+0w

*** 3.6.1

   0:  118.947u 0.028s 1:59.10 99.8%   0+0k 0+0io 0pf+0w
-20:  118.023u 0.008s 1:58.06 99.9%   0+0k 0+0io 0pf+0w

===== grenadine.pov

*** 3.7.0.beta14

1 thread,    0:   60.591u 0.056s 1:01.06 99.3%    0+0k 0+0io 0pf+0w
1 thread,  -20:   59.947u 0.036s 1:00.24 99.5%    0+0k 0+0io 0pf+0w

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