[Trilinos-Users] [EXTERNAL] Re: AMG Preconditioner Neumann Laplacian 32 vs 64 bit issue
Martin Stoll
martin.stoll80 at gmail.com
Mon Dec 5 00:37:29 MST 2011
Dear Ray and Alberto,
thanks very much for your help. I now changed the coarse solver to an
iterative one and everything works nicely.
Best,
Martin
2011/12/2 Alberto F. Martín-Huertas <amartin at cimne.upc.edu>
> Hi Martin,
>
> I guess that this funky thing Ray is referring
> to is highly sensitive to rounding errors, which
> in turn depend on the compiler/architecture. This may
> explain why you are observing a different behaviour
> among both machines.
>
> Regards,
> Alberto.
>
>
>
> On Thu, 1 Dec 2011 21:42:18 +0100, Martin Stoll wrote:
>
>> Hi Ray,
>>
>> thanks for this. It is indeed very useful to know, I guess I should
>> have known already.
>>
>> Do you see any reason why my 32bit machine gets away with the same
>> setup?
>>
>> Martin
>>
>> On Thu, Dec 1, 2011 at 9:28 PM, Tuminaro, Raymond S wrote:
>>
>> My guess is that you have understood the issue ... but just in case
>>> it was not totally clear. ML's interpolation
>>> is exact for constants. This means that the coarsest level matrix
>>> is still singular. We then use a direct solver
>>> for this system (by default). The direct solver might do something
>>> funky with the singular system, and
>>> then ML will happily interpolate this funky thing up the
>>> hierarchy. ML often works with singular systems, but
>>> it is always a bit scary and it is best to just do an iterative
>>> solve for the coarsest level system.
>>> -Ray
>>>
>>> -------------------------
>>>
>>> FROM: Martin Stoll [martin.stoll80 at gmail.com [18]]
>>> SENT: Thursday, December 01, 2011 12:16 PM
>>> TO: Tuminaro, Raymond S
>>> CC: Alberto F. Martín-Huertas; trilinos-users at software.**sandia.gov<trilinos-users at software.sandia.gov>
>>> [19]
>>> SUBJECT: Re: [EXTERNAL] Re: [Trilinos-Users] AMG Preconditioner
>>>
>>> Neumann Laplacian 32 vs 64 bit issue
>>>
>>> Dear Ray,
>>>
>>> thanks for the comments.
>>>
>>> Yes, the Neumann Laplacian is indeed singular. In fact, from
>>> within dealII I simply use the ML AMG preconditioner as a black box
>>> as there are only a few parameters I can play with. In my case
>>> usually, type of smoother, smoother steps and number of cycles. So
>>>
>> I
>>
>>> am not really aware what is happening within ML and I go with all
>>> the default settings. I am sorry for being so ignorant but I never
>>> had any problems. Only when I moved my code to a different machine
>>> running 64 bits I was having problems. Again, same version of
>>>
>> dealII
>>
>>> and trilinos on my mac runs smoothly.
>>>
>>> I will look into changing some options from within deal.II to try
>>> a different solver for the coarse grid and hope for the best.
>>>
>>> Thanks again for the comments.
>>>
>>> Best,
>>> Martin
>>>
>>> 2011/12/1 Tuminaro, Raymond S
>>>
>>> So, I'm guessing that the Neumann Laplacian is singular. Are
>>>> you using a direct solve on the coarsest grid? Depending on how
>>>> things are handled here ... you might get different results. You
>>>> might try switching to an
>>>> iterative method on the coarsest level and see what happens.
>>>>
>>>> -Ray
>>>>
>>>> -------------------------
>>>>
>>>> FROM: trilinos-users-bounces@**software.sandia.gov<trilinos-users-bounces at software.sandia.gov>[10]
>>>> [trilinos-users-bounces@**software.sandia.gov<trilinos-users-bounces at software.sandia.gov>[11]] on behalf of
>>>> Martin Stoll [martin.stoll80 at gmail.com [12]]
>>>> SENT: Thursday, December 01, 2011 4:29 AM
>>>> TO: Alberto F. Martín-Huertas
>>>> CC: trilinos-users at software.**sandia.gov<trilinos-users at software.sandia.gov>[13]
>>>> SUBJECT: [EXTERNAL] Re: [Trilinos-Users] AMG Preconditioner
>>>>
>>>> Neumann Laplacian 32 vs 64 bit issue
>>>>
>>>> Hi Alberto,
>>>> thanks for your comment.
>>>>
>>>> I just tried the Dirichlet Laplacian on the velocity space,
>>>> the Neumann Laplacian was on the pressure space, and that worked
>>>> fine.
>>>>
>>>> As I said on my laptop and the 32 bit desktop everything work
>>>> but when I switch to the 64 bit machine the outcome is quite
>>>> different. Our software engineer also tried different versions of
>>>> trilinos (currently 10.4.2, which is recommended by the deal.II
>>>> developers). My Desktop uses trilinos 9.03 and my laptop 10.4.2
>>>> and they both work fine.
>>>>
>>>> Any help is greatly appreciated.
>>>>
>>>> Best,
>>>> Martin
>>>>
>>>> 2011/12/1 Alberto F. Martín-Huertas
>>>>
>>>> Hi Martin,
>>>>>
>>>>> did you observe the same behaviour with a
>>>>> Dirichlet Laplacian ?
>>>>>
>>>>> Best regards,
>>>>> Alberto.
>>>>>
>>>>> On Thu, 1 Dec 2011 12:52:08 +0100, Martin Stoll wrote:
>>>>> > Hi all,
>>>>> >
>>>>> > I am using deal.II and from there call the ML AMG
>>>>> preconditioner. I
>>>>> > am using it to approximate a Neumann Laplacian, which works
>>>>> like a
>>>>> > charm on
>>>>> > my 32 bit desktop Ubuntu machine and also on my Mac Book Pro
>>>>> running
>>>>> > Snow Leopard. Now copying this to a linux 64 bit machine I
>>>>> get weird
>>>>> > results meaning
>>>>> > that applying the preconditioner results
>>>>> > 32 bit
>>>>> > norm(vin)=0.01
>>>>> > APPLY AMG
>>>>> > norm(vout)=0.15
>>>>> >
>>>>> > 64 bit
>>>>> > norm(vin)=0.01
>>>>> > APPLY AMG
>>>>> > norm(vout)=1e+11
>>>>> >
>>>>> > When instead of the Neumann Laplacian I put a mass matrix
>>>>> into the
>>>>> > AMG routine the blow does not happen.
>>>>> >
>>>>> > I am not sure where to go from here so I hope I could get
>>>>> some help
>>>>> > here.
>>>>> >
>>>>> > Best,
>>>>> > Martin
>>>>> >
>>>>> > --
>>>>> > Martin Stoll
>>>>> > Postdoctoral Research Fellow
>>>>> >
>>>>> > Computational Methods in Systems and Control Theory
>>>>> >
>>>>> > Max Planck Institute for Dynamics of Complex Technical
>>>>> Systems
>>>>> > Sandtorstr. 1, D-39106 Magdeburg,Germany
>>>>> > Email: martin.stoll80 at gmail.com [1] [1]
>>>>> > URL: http://www.mpi-magdeburg.**mpg.de/mpcsc/stollm/<http://www.mpi-magdeburg.mpg.de/mpcsc/stollm/>[2] [2]
>>>>>
>>>>>
>>>>>> > Tel :+49 391 6110 384 [3]
>>>>> >
>>>>> >
>>>>> >
>>>>> > Links:
>>>>> > ------
>>>>> > [1] mailto:stollm at mpi-magdeburg.**mpg.de<stollm at mpi-magdeburg.mpg.de>[4]
>>>>> > [2] http://www.mpi-magdeburg.mpg.**de/mpcsc/stollm/<http://www.mpi-magdeburg.mpg.de/mpcsc/stollm/>[5]
>>>>>
>>>>>
>>>>> --
>>>>> Alberto F. Martín-Huertas
>>>>> Centre Internacional de Mètodes Numèrics a l'Enginyeria
>>>>> (CIMNE)
>>>>> Parc Mediterrani de la Tecnologia, UPC
>>>>> Esteve Terrades 5, Building C3, Office 210,
>>>>> 08860 Castelldefels (Barcelona, Spain)
>>>>> Tel.: (+34) 9341 34223 [6]
>>>>> e-mail: amartin at cimne.upc.edu [7]
>>>>>
>>>>>
>>>>> ________________
>>>>> IMPORTANT NOTICE
>>>>> All personal data contained on this mail will be processed
>>>>> confidentially and registered in a file property of CIMNE in
>>>>> order to manage corporate communications. You may exercise
>>>>> the rights
>>>>> of access, rectification, erasure and object by
>>>>> letter sent to Ed. C1 Campus Norte UPC. Gran Capitán s/n
>>>>> Barcelona.
>>>>>
>>>>> ______________________________**_________________
>>>>> Trilinos-Users mailing list
>>>>> Trilinos-Users at software.**sandia.gov<Trilinos-Users at software.sandia.gov>[8]
>>>>> http://software.sandia.gov/**mailman/listinfo/trilinos-**users<http://software.sandia.gov/mailman/listinfo/trilinos-users>[9]
>>>>>
>>>>
>>>> --
>>>> Martin Stoll
>>>> Postdoctoral Research Fellow
>>>>
>>>> Computational Methods in Systems and Control Theory
>>>> Max Planck Institute for Dynamics of Complex Technical Systems
>>>> Sandtorstr. 1, D-39106 Magdeburg,Germany
>>>>
>>>> Email: martin.stoll80 at gmail.com [15]
>>>>
>>>> URL: http://www.mpi-magdeburg.**mpg.de/mpcsc/stollm/<http://www.mpi-magdeburg.mpg.de/mpcsc/stollm/>[16]
>>>>
>>>> Tel :+49 391 6110 384 [17]
>>>>
>>>
>>> --
>>> Martin Stoll
>>> Postdoctoral Research Fellow
>>>
>>> Computational Methods in Systems and Control Theory
>>> Max Planck Institute for Dynamics of Complex Technical Systems
>>> Sandtorstr. 1, D-39106 Magdeburg,Germany
>>>
>>> Email: martin.stoll80 at gmail.com [21]
>>>
>>> URL: http://www.mpi-magdeburg.**mpg.de/mpcsc/stollm/<http://www.mpi-magdeburg.mpg.de/mpcsc/stollm/>[22]
>>>
>>> Tel :+49 391 6110 384 [23]
>>>
>>
>> --
>> Martin Stoll
>> Postdoctoral Research Fellow
>>
>> Computational Methods in Systems and Control Theory
>> Max Planck Institute for Dynamics of Complex Technical Systems
>> Sandtorstr. 1, D-39106 Magdeburg,Germany
>> Email: martin.stoll80 at gmail.com [25]
>>
>> URL: http://www.mpi-magdeburg.**mpg.de/mpcsc/stollm/<http://www.mpi-magdeburg.mpg.de/mpcsc/stollm/>[26]
>>
>>
>> Tel :+49 391 6110 384
>>
>>
>>
>> Links:
>> ------
>> [1] mailto:martin.stoll80 at gmail.**com <martin.stoll80 at gmail.com>
>> [2] http://www.mpi-magdeburg.mpg.**de/mpcsc/stollm/<http://www.mpi-magdeburg.mpg.de/mpcsc/stollm/>
>> [3] http://webmail.cimne.upc.edu/**tel:%2B49%20391%206110%20384<http://webmail.cimne.upc.edu/tel:%2B49%20391%206110%20384>
>> [4] mailto:stollm at mpi-magdeburg.**mpg.de <stollm at mpi-magdeburg.mpg.de>
>> [5] http://www.mpi-magdeburg.mpg.**de/mpcsc/stollm/<http://www.mpi-magdeburg.mpg.de/mpcsc/stollm/>
>> [6] http://webmail.cimne.upc.edu/**tel:%28%2B34%29%209341%2034223<http://webmail.cimne.upc.edu/tel:%28%2B34%29%209341%2034223>
>> [7] mailto:amartin at cimne.upc.edu
>> [8] mailto:Trilinos-Users@**software.sandia.gov<Trilinos-Users at software.sandia.gov>
>> [9] http://software.sandia.gov/**mailman/listinfo/trilinos-**users<http://software.sandia.gov/mailman/listinfo/trilinos-users>
>> [10] mailto:trilinos-users-bounces@**software.sandia.gov<trilinos-users-bounces at software.sandia.gov>
>> [11] mailto:trilinos-users-bounces@**software.sandia.gov<trilinos-users-bounces at software.sandia.gov>
>> [12] mailto:martin.stoll80 at gmail.**com <martin.stoll80 at gmail.com>
>> [13] mailto:trilinos-users@**software.sandia.gov<trilinos-users at software.sandia.gov>
>> [14] mailto:amartin at cimne.upc.edu
>> [15] mailto:stollm at mpi-magdeburg.**mpg.de <stollm at mpi-magdeburg.mpg.de>
>> [16] http://www.mpi-magdeburg.mpg.**de/mpcsc/stollm/<http://www.mpi-magdeburg.mpg.de/mpcsc/stollm/>
>> [17] http://webmail.cimne.upc.edu/**tel:%2B49%20391%206110%20384<http://webmail.cimne.upc.edu/tel:%2B49%20391%206110%20384>
>> [18] mailto:martin.stoll80 at gmail.**com <martin.stoll80 at gmail.com>
>> [19] mailto:trilinos-users@**software.sandia.gov<trilinos-users at software.sandia.gov>
>> [20] mailto:rstumin at sandia.gov
>> [21] mailto:stollm at mpi-magdeburg.**mpg.de <stollm at mpi-magdeburg.mpg.de>
>> [22] http://www.mpi-magdeburg.mpg.**de/mpcsc/stollm/<http://www.mpi-magdeburg.mpg.de/mpcsc/stollm/>
>> [23] http://webmail.cimne.upc.edu/**tel:%2B49%20391%206110%20384<http://webmail.cimne.upc.edu/tel:%2B49%20391%206110%20384>
>> [24] mailto:rstumin at sandia.gov
>> [25] mailto:stollm at mpi-magdeburg.**mpg.de <stollm at mpi-magdeburg.mpg.de>
>> [26] http://www.mpi-magdeburg.mpg.**de/mpcsc/stollm/<http://www.mpi-magdeburg.mpg.de/mpcsc/stollm/>
>>
>
> --
> Alberto F. Martín-Huertas
> Centre Internacional de Mètodes Numèrics a l'Enginyeria (CIMNE)
> Parc Mediterrani de la Tecnologia, UPC
> Esteve Terrades 5, Building C3, Office 210,
> 08860 Castelldefels (Barcelona, Spain)
> Tel.: (+34) 9341 34223
> e-mail: amartin at cimne.upc.edu
>
> ________________
> IMPORTANT NOTICE
> All personal data contained on this mail will be processed confidentially
> and registered in a file property of CIMNE in
> order to manage corporate communications. You may exercise the rights of
> access, rectification, erasure and object by
> letter sent to Ed. C1 Campus Norte UPC. Gran Capitán s/n Barcelona.
>
--
Martin Stoll
Postdoctoral Research Fellow
Computational Methods in Systems and Control Theory
Max Planck Institute for Dynamics of Complex Technical Systems
Sandtorstr. 1, D-39106 Magdeburg,Germany
Email: martin.stoll80 at gmail.com <stollm at mpi-magdeburg.mpg.de>
URL: http://www.mpi-magdeburg.mpg.de/mpcsc/stollm/
Tel :+49 391 6110 384
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