[cpp-threads] cpp-threads Digest, Vol 38, Issue 1
Michael Wong
michaelw at ca.ibm.com
Thu Aug 5 15:10:19 BST 2010
Ok, will update if we think this is good. Thanks.
Regards, Michael
Rational C/C++ cafe:
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Boost test results
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Michael Wong
XL C++ Compiler kernel Development
IBM Canada Ltd., C2/KD2/8200/MKM
8200 Warden Avenue
Markham, Ontario L6G 1C7
W:905-413-3283 F:905-413-4839
Re: [cpp-threads] cpp-threads Digest, Vol 38, Issue 1
Mark Batty
to:
cpp-threads
08/05/2010 08:47 AM
Sent by:
cpp-threads-bounces at decadent.org.uk
Please respond to C++ threads standardisation
The proposal looks good for the most part, but there are two changes
that would be good to make. Firstly, we have a proof that with the
added coherence axioms, visible sequences of side effects are unique,
so I suggest adding the following note to 1.10p13 (this addresses
Paul's comment):
"[Note - It can be shown that the visible sequence of side effects of
a value computation is unique given the coherence requirements below.
- end note]"
Secondly, in the Read-Read requirement, B gets its value indirectly,
taking the value of A (another read). The following wording is more
direct:
"-Read Read:
If a value computation A of an atomic object M happens before a value
computation B of M, and A takes its value from the side effect X, then
the value computed by B shall either be the value stored by X, or the
value stored by a side effect Y, where Y follows X in the
modification order of M."
I hope the rest of the meeting is going well,
Mark
On Thu, Aug 5, 2010 at 12:00 PM, <cpp-threads-request at decadent.org.uk>
wrote:
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> Today's Topics:
>
> 1. Coherence Requirement wording changes for 1.10p13 (Michael Wong)
> 2. Re: Coherence Requirement wording changes for 1.10p13
> (Paul E. McKenney)
> 3. Re: Coherence Requirement wording changes for 1.10p13 (Hans Boehm)
> 4. Re: Coherence Requirement wording changes for 1.10p13
> (Peter Dimov)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Tue, 3 Aug 2010 16:52:53 -0400
> From: Michael Wong <michaelw at ca.ibm.com>
> Subject: [cpp-threads] Coherence Requirement wording changes for
> 1.10p13
> To: cpp-threads at decadent.org.uk
> Message-ID:
>
<OFDD7C8FC8.8576BBB0-ON85257774.00722617-85257774.0072B28D at ca.ibm.com>
> Content-Type: text/plain; charset="us-ascii"
>
>
>
> Hi all, Benjamin Kosnick and I have made the following updates to the
> coherence requirement paragraph based on today session with Peter Sewell
> and Mark Batty. It is available for viewing on the Rapperswil concurrence
> wiki:
>
http://wiki.dinkumware.com/twiki/pub/Wg21rapperswil/ConcurrencyWorkingGroup/Coherence_Requirement.html
>
> This is to fix several NB comments GB 11, GB 12, CA 18, CA 19, CA 20.
> We are asking for feedback comments of this restructuring and the
insertion
> of the new paragraphs for CORW and COWR as outlined in Sections 2.1 and
2.2
> in their paper:
>
http://wiki.dinkumware.com/twiki/pub/Wg21rapperswil/ConcurrencyWorkingGroup/cpp-fcd-01.pdf
>
> This will not be voted at the end of this week, but we want to have this
> early drafting ready for review comment to make sure we are heading in
the
> right direction, and if all goes well, we propose to potentially add
> diagrams of each of the coherence requirements as discussed today.
>
> Thanks.
>
> Regards, Michael
>
> Rational C/C++ cafe:
> http://www.ibm.com/software/rational/cafe/community/ccpp
> My Blogs:
> Parallel & Multi-Core Computing
> http://www.ibm.com/software/rational/cafe/blogs/ccpp-parallel-multicore
> C++ Language & Standard
> http://www.ibm.com/software/rational/cafe/blogs/cpp-standard
> Commercial Computing
> http://www.ibm.com/software/rational/cafe/blogs/ccpp-commercial
> Boost test results
>
http://www.ibm.com/support/docview.wss?rs=2239&context=SSJT9L&uid=swg27006911
>
> C/C++ Compilers Support Page
> http://www.ibm.com/software/awdtools/ccompilers/support/
> C/C++ Feature Request Interface
> http://www.ibm.com/support/docview.wss?uid=swg27005811
> XL Fortran Compiler Support Page
> http://www.ibm.com/software/awdtools/fortran/xlfortran/support/
> XL Fortran Feature Request Interface
> http://www.ibm.com/support/docview.wss?uid=swg27005812
>
> Michael Wong
> XL C++ Compiler kernel Development
> IBM Canada Ltd., C2/KD2/8200/MKM
> 8200 Warden Avenue
> Markham, Ontario L6G 1C7
> W:905-413-3283 F:905-413-4839
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> ------------------------------
>
> Message: 2
> Date: Wed, 4 Aug 2010 17:53:13 -0700
> From: "Paul E. McKenney" <paulmck at linux.vnet.ibm.com>
> Subject: Re: [cpp-threads] Coherence Requirement wording changes for
> 1.10p13
> To: C++ threads standardisation <cpp-threads at decadent.org.uk>
> Message-ID: <20100805005312.GQ24163 at linux.vnet.ibm.com>
> Content-Type: text/plain; charset=us-ascii
>
> On Tue, Aug 03, 2010 at 04:52:53PM -0400, Michael Wong wrote:
>>
>>
>> Hi all, Benjamin Kosnick and I have made the following updates to the
>> coherence requirement paragraph based on today session with Peter Sewell
>> and Mark Batty. It is available for viewing on the Rapperswil
concurrence
>> wiki:
>>
http://wiki.dinkumware.com/twiki/pub/Wg21rapperswil/ConcurrencyWorkingGroup/Coherence_Requirement.html
>>
>> This is to fix several NB comments GB 11, GB 12, CA 18, CA 19, CA 20.
>> We are asking for feedback comments of this restructuring and the
insertion
>> of the new paragraphs for CORW and COWR as outlined in Sections 2.1 and
2.2
>> in their paper:
>>
http://wiki.dinkumware.com/twiki/pub/Wg21rapperswil/ConcurrencyWorkingGroup/cpp-fcd-01.pdf
>>
>> This will not be voted at the end of this week, but we want to have this
>> early drafting ready for review comment to make sure we are heading in
the
>> right direction, and if all goes well, we propose to potentially add
>> diagrams of each of the coherence requirements as discussed today.
>
> Hello, Michael,
>
> I like the way this breaks out the write/write, read/read, ... cases!
>
> But given the restrictions imposed by these cases, is it really possible
> to have more than one visible sequence of side effects?
>
> Thanx, Paul
>
>
>
> ------------------------------
>
> Message: 3
> Date: Wed, 4 Aug 2010 21:48:36 -0700 (PDT)
> From: Hans Boehm <Hans.Boehm at hp.com>
> Subject: Re: [cpp-threads] Coherence Requirement wording changes for
> 1.10p13
> To: C++ threads standardisation <cpp-threads at decadent.org.uk>
> Message-ID: <alpine.LNX.1.10.1008042131590.25429 at 192.168.2.2>
> Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed
>
>
> I looked at this and the corresponding section of the Batty et al paper.
> The changes look good to me. The WriteRead issue looks like a
> longstanding bug, with the ReadWrite issue getting more recently
> introduced.
>
> (I wasn't immediately convinced by the WriteRead example, since I think
> there is nothing in the example forcing the f->c modification order.
> But on second thought it's trivial to enforce such a constraint.)
>
> It's great that we have a proposed fix. But I also agree that this needs
> some baking time.
>
> Hans
>
> On Tue, 3 Aug 2010, Michael Wong wrote:
>
>>
>> Hi all, Benjamin Kosnick and I have made the following updates to the
>> coherence requirement paragraph based on today session with Peter Sewell
>> and Mark Batty. It is available for viewing on the Rapperswil
concurrence
>> wiki:
>>
http://wiki.dinkumware.com/twiki/pub/Wg21rapperswil/ConcurrencyWorkingGroup/Cohe>>
>> rence_Requirement.html
>>
>> This is to fix several NB comments GB 11, GB 12, CA 18, CA 19, CA 20.
>> We are asking for feedback comments of this restructuring and the
>> insertion of the new paragraphs for CORW and COWR as outlined in
Sections
>> 2.1 and 2.2 in their paper:
>>
http://wiki.dinkumware.com/twiki/pub/Wg21rapperswil/ConcurrencyWorkingGroup/cpp-,
>> fcd-01.pdf
>>
>> This will not be voted at the end of this week, but we want to have this
>> early drafting ready for review comment to make sure we are heading in
>> the right direction, and if all goes well, we propose to potentially add
>> diagrams of each of the coherence requirements as discussed today.
>>
>> Thanks.
>>
>> Regards, Michael
>>
>> Rational C/C++ cafe:
>> http://www.ibm.com/software/rational/cafe/community/ccpp
>> My Blogs:
>> Parallel & Multi-Core Computing
>> http://www.ibm.com/software/rational/cafe/blogs/ccpp-parallel-multicore
>> C++ Language & Standard
>> http://www.ibm.com/software/rational/cafe/blogs/cpp-standard
>> Commercial Computing
>> http://www.ibm.com/software/rational/cafe/blogs/ccpp-commercial
>> Boost test results
>>
http://www.ibm.com/support/docview.wss?rs=2239&context=SSJT9L&uid=swg27006911
>> C/C++ Compilers Support Page
>> http://www.ibm.com/software/awdtools/ccompilers/support/
>> C/C++ Feature Request Interface
>> http://www.ibm.com/support/docview.wss?uid=swg27005811
>> XL Fortran Compiler Support Page
>> http://www.ibm.com/software/awdtools/fortran/xlfortran/support/
>> XL Fortran Feature Request Interface
>> http://www.ibm.com/support/docview.wss?uid=swg27005812
>>
>> Michael Wong
>> XL C++ Compiler kernel Development
>> IBM Canada Ltd., C2/KD2/8200/MKM
>> 8200 Warden Avenue
>> Markham, Ontario L6G 1C7
>> W:905-413-3283 F:905-413-4839
>>
>>
>>
>
>
>
> ------------------------------
>
> Message: 4
> Date: Thu, 5 Aug 2010 13:12:45 +0300
> From: "Peter Dimov" <pdimov at mmltd.net>
> Subject: Re: [cpp-threads] Coherence Requirement wording changes for
> 1.10p13
> To: "C++ threads standardisation" <cpp-threads at decadent.org.uk>
> Message-ID: <1346A4310B014CC5A2714B574768AB12 at pdimov5>
> Content-Type: text/plain; format=flowed; charset="iso-8859-1";
> reply-type=response
>
> Hans Boehm wrote:
>> I looked at this and the corresponding section of the Batty et al paper.
>> The changes look good to me. The WriteRead issue looks like a
>> longstanding bug, with the ReadWrite issue getting more recently
>> introduced.
>
> Looks good to me, too. I view this as a formalization of the old
requirement
> that the happens-before order and the modification order should be
> "consistent" - this spells out what consistency means.
>
>
>
>
> ------------------------------
>
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>
> End of cpp-threads Digest, Vol 38, Issue 1
> ******************************************
>
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