POV-Ray : Newsgroups : povray.bugreports : Probable thread safety issue in functions using splines. 3.7.0.RC7. Server Time
12 Jun 2024 18:30:02 EDT (-0400)
  Probable thread safety issue in functions using splines. 3.7.0.RC7. (Message 1 to 7 of 7)  
From: William F Pokorny
Subject: Probable thread safety issue in functions using splines. 3.7.0.RC7.
Date: 3 Jun 2013 06:54:08
Message: <51ac75d0$1@news.povray.org>
Hi,
I believe I've hit a thread safety issue. Could someone confirm? Running 
Ubuntu 12.1. I'll also post images to p.b.images.

Thanks for your time.
Bill P.


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From: waggy
Subject: Re: Probable thread safety issue in functions using splines. 3.7.0.RC7.
Date: 3 Jun 2013 15:00:00
Message: <web.51ace69c288b02da21be1230@news.povray.org>
William F Pokorny wrote:
> I believe I've hit a thread safety issue. Could someone confirm? Running
> Ubuntu 12.1. I'll also post images to p.b.images.

I see the same behavior under Ubuntu 12.04, AMD 2431 CPU, Linux 3.2.0-45 kernel.
The artifacts appear for any value of worker threads (+WTn) when n is greater
than 1. The artifacts differ with each render, even for the same number of
worker threads.

I rendered it using 3.7.0.RC7 (g++ 4.6 @x86_64-unknown-linux-gnu) as follows:
povray +P +WT6 somefilename.pov

FWIW, using povray -D +WT6 somefilename.pov yields similar results.


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From: Cousin Ricky
Subject: Re: Probable thread safety issue in functions using splines. 3.7.0.RC7.
Date: 3 Jun 2013 15:20:01
Message: <web.51aceb7a288b02da78641e0c0@news.povray.org>
William F Pokorny <ano### [at] anonymousorg> wrote:
> I believe I've hit a thread safety issue. Could someone confirm? Running
> Ubuntu 12.1. I'll also post images to p.b.images.

Confirmed with openSUSE 12.2.

I don't have an answer to this problem, but I can tell you that you'll get a
much faster render if you change the contained_by to box { <-0.5,-2.0,-0.5>,
<0.5,2.0,0.5> } and set max_gradient to 28.

To the POV Team:  Last year I posted to p.beta-test that POV-Ray 3.7 did not
always post the warning for a bad max_gradient value, but could not reproduce
the problem with a simplified scene.  Well, serendipity has come to the rescue,
and I cannot raise the max_gradient warning with Mr. Pokorny's scene either.


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From: waggy
Subject: Re: Probable thread safety issue in functions using splines. 3.7.0.RC7.
Date: 3 Jun 2013 15:25:01
Message: <web.51acec83288b02da21be1230@news.povray.org>
Here's another data point. The artifacts also appear under the following
conditions, tested with the default (16) worker threads.

POV-Ray 3.7.0.RC7 (icpc 13.1.0 @x86_64-unknown-linux-gnu)
Intel(R) Xeon(R) CPU E5-2680 0 @ 2.70GHz

uname -or
2.6.32-279.14.1.el6.x86_64 GNU/Linux

lsb_release -irc
Distributor ID: CentOS
Release:        6.3
Codename:       Final


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From: Le Forgeron
Subject: Re: Probable thread safety issue in functions using splines. 3.7.0.RC7.
Date: 3 Jun 2013 17:51:41
Message: <51ad0fed$1@news.povray.org>
Le 03/06/2013 12:54, William F Pokorny nous fit lire :
> Hi,
> I believe I've hit a thread safety issue. Could someone confirm? Running
> Ubuntu 12.1. I'll also post images to p.b.images.
> 
> Thanks for your time.
> Bill P.
> 
> 
> SplineThreadSafety.pov
> 
> 
>
//----------------------------------------------------------------------------------------------------
> // Scene to show thread safet issue with splines - or maybe functions using splines.
> //
> // On a multi-core machine, without AA, run this command to see the problem (8 cores
< 60 seconds) :
> //

that might be less than 60 seconds, but with Intel Inspector (XE 2013),
it becomes 42:50 (just 14 data races, oh well, that's just so friendly).

ID  Type Sources Modules State
P1  Data race isosurf.cpp; mutex.hpp povray New
P2  Data race mutex.hpp; povms.cpp povray New
P3  Data race povray.cpp povray New
P4  Data race povray.cpp povray New
P5  Data race mutex.hpp; pov_mem.cpp; splines.cpp povray New
P6  Data race mutex.hpp; pov_mem.cpp; splines.cpp povray New
P7  Data race mutex.hpp; pov_mem.cpp; splines.cpp povray New
P8  Data race recursive_mutex.hpp; scene.cpp; task.cpp; taskqueue.cpp;
view.cpp povray New
P9  Data race condition_variable.hpp; vfe.cpp; vfesession.cpp povray New
P10  Data race condition_variable.hpp; unixconsole.cpp; vfesession.cpp
povray New
P11  Data race condition_variable.hpp; unixconsole.cpp; vfesession.cpp
povray New
P12  Data race unixconsole.cpp; vfesession.cpp; vfesession.h povray New
P13  Data race unixconsole.cpp; vfesession.cpp povray New
P14  Data race [Unknown]; unixconsole.cpp; vfesession.cpp
libboost_thread.so.1.49.0; povray New

Numbers 2, 3, 4, 8, 9, 10, 11, 12, 13 & 14 are related to the handling
of session (and occur once or twice only, excepted #8, four times).

Number 1 is about isosurface (adjusting gradient at isosurf.cpp:1099 vs
1098 (testing its value), and copying the isosurface) (IMHO, rendering
threads updating the object... not the best move without some
atomic/protection (and not sure a DBL is/can be atomic)) (occurs 2505
times).

Number 5, 6 and 7 are about splines
* sp->Cache_Type & Cache_Point, splines.cpp :803 vs :814/815 (2024 times)
* sp->Cache_Valid, :805 vs :813 vs :904 (1770 times)
* sp->Cache_Data, :807 vs :903 (5025 times)

Only my 0.02¢ (yes, very cheap), but it seems to confirm.


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From: William F Pokorny
Subject: Re: Probable thread safety issue in functions using splines. 3.7.0.RC7.
Date: 4 Jun 2013 06:57:37
Message: <51adc821@news.povray.org>
On 06/03/2013 05:51 PM, Le_Forgeron wrote:
> Le 03/06/2013 12:54, William F Pokorny nous fit lire :
>> Hi,
>> I believe I've hit a thread safety issue. Could someone confirm? Running
>> Ubuntu 12.1. I'll also post images to p.b.images.
>>
>> Thanks for your time.
>> Bill P.
>>
>>
>> SplineThreadSafety.pov
>>
>>
>>
//----------------------------------------------------------------------------------------------------
>> // Scene to show thread safet issue with splines - or maybe functions using
splines.
>> //
>> // On a multi-core machine, without AA, run this command to see the problem (8
cores < 60 seconds) :
>> //
>
> that might be less than 60 seconds, but with Intel Inspector (XE 2013),
> it becomes 42:50 (just 14 data races, oh well, that's just so friendly).
>
> ID  Type Sources Modules State
> P1  Data race isosurf.cpp; mutex.hpp povray New
> P2  Data race mutex.hpp; povms.cpp povray New
> P3  Data race povray.cpp povray New
> P4  Data race povray.cpp povray New
> P5  Data race mutex.hpp; pov_mem.cpp; splines.cpp povray New
> P6  Data race mutex.hpp; pov_mem.cpp; splines.cpp povray New
> P7  Data race mutex.hpp; pov_mem.cpp; splines.cpp povray New
> P8  Data race recursive_mutex.hpp; scene.cpp; task.cpp; taskqueue.cpp;
> view.cpp povray New
> P9  Data race condition_variable.hpp; vfe.cpp; vfesession.cpp povray New
> P10  Data race condition_variable.hpp; unixconsole.cpp; vfesession.cpp
> povray New
> P11  Data race condition_variable.hpp; unixconsole.cpp; vfesession.cpp
> povray New
> P12  Data race unixconsole.cpp; vfesession.cpp; vfesession.h povray New
> P13  Data race unixconsole.cpp; vfesession.cpp povray New
> P14  Data race [Unknown]; unixconsole.cpp; vfesession.cpp
> libboost_thread.so.1.49.0; povray New
>
> Numbers 2, 3, 4, 8, 9, 10, 11, 12, 13 & 14 are related to the handling
> of session (and occur once or twice only, excepted #8, four times).
>
> Number 1 is about isosurface (adjusting gradient at isosurf.cpp:1099 vs
> 1098 (testing its value), and copying the isosurface) (IMHO, rendering
> threads updating the object... not the best move without some
> atomic/protection (and not sure a DBL is/can be atomic)) (occurs 2505
> times).
>
> Number 5, 6 and 7 are about splines
> * sp->Cache_Type & Cache_Point, splines.cpp :803 vs :814/815 (2024 times)
> * sp->Cache_Valid, :805 vs :813 vs :904 (1770 times)
> * sp->Cache_Data, :807 vs :903 (5025 times)
>
> Only my 0.02¢ (yes, very cheap), but it seems to confirm.
>

Thanks everyone for the confirmation, the code tips - and the cents ;-). 
The Intel Inspector tool is news to me. I'm actually impressed at how 
"quickly" it ran what must of been heavily instrumented code.

I'll make my first run at opening an official bug report after work 
tonight.

Bill P.


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From: MichaelJF
Subject: Re: Probable thread safety issue in functions using splines. 3.7.0.RC7.
Date: 4 Jun 2013 12:55:01
Message: <web.51ae1ab3288b02daab56f9610@news.povray.org>
> Thanks everyone for the confirmation, the code tips - and the cents ;-).
> The Intel Inspector tool is news to me. I'm actually impressed at how
> "quickly" it ran what must of been heavily instrumented code.
>
> I'll make my first run at opening an official bug report after work
> tonight.
>
> Bill P.

Just to add to the system list: with Windows and a core i7 one yields the same
result.

Best regards,
Michael


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