[petsc-users] Problem with Mat.setpreallocationNNZ in petsc4py

[Xin Zhao]

Thanks. Than Than Thanks.

On Sat, Jul 7, 2012 at 6:17 PM, Matthew Knepley <knepley at gmail.com> wrote:

> On Sat, Jul 7, 2012 at 11:08 AM, Xin Zhao <sean.null at gmail.com> wrote:
>
>> So if it is written as
>> if PETSc.COMM_WORLD.get_Rank() == 0:
>> L.setPreallocationNNZ((3,2))
>>
>> will it achieve what I intend to do?
>>
>
> No. No no no. You do not have to call setPreallocation(). That is why I
> said (twice) that
> the matrix is already preallocated. If something is "already
> preallocated", it does not
> have to be allocated again.
>
>    Matt
>
>
>>
>>
>> On Sat, Jul 7, 2012 at 6:04 PM, Matthew Knepley <knepley at gmail.com>wrote:
>>
>>> On Sat, Jul 7, 2012 at 11:02 AM, Xin Zhao <sean.null at gmail.com> wrote:
>>>
>>>> yeap...sorry...
>>>> L=DA.createMat()
>>>>
>>>> then
>>>> L.setPreallocationNNZ((3,2))
>>>>
>>>
>>> As I said, its already preallocated.
>>>
>>>   Matt
>>>
>>>
>>>> On Sat, Jul 7, 2012 at 6:01 PM, Matthew Knepley <knepley at gmail.com>wrote:
>>>>
>>>>> On Sat, Jul 7, 2012 at 10:58 AM, Xin Zhao <sean.null at gmail.com> wrote:
>>>>>
>>>>>> Dear all,
>>>>>>
>>>>>> I generate a matrix L by
>>>>>> DA =PETSc.DA().create(...some...)
>>>>>> L = DA.create()
>>>>>>
>>>>>
>>>>> Is this createMatrix()? The matrix returned from a DA is already
>>>>> preallocated.
>>>>>
>>>>>    Matt
>>>>>
>>>>>
>>>>>> Then I want to preallocate memory for L
>>>>>> L.setPreallocationNNZ((3,2))
>>>>>> This works when for mpiexec -np 1
>>>>>> but it gives the error message below when mpiexec -np 4
>>>>>>
>>>>>> [3] MatAnyAIJSetPreallocation() line 311 in
>>>>>> petsc4py-1.2/src/include/custom.h
>>>>>> [3] Operation done in wrong order
>>>>>> [3] matrix is already preallocated
>>>>>>
>>>>>> How to solve this?
>>>>>>
>>>>>> Thanks in advance.
>>>>>>
>>>>>> Cheers,
>>>>>> Xin
>>>>>>
>>>>>
>>>>>
>>>>>
>>>>> --
>>>>> What most experimenters take for granted before they begin their
>>>>> experiments is infinitely more interesting than any results to which their
>>>>> experiments lead.
>>>>> -- Norbert Wiener
>>>>>
>>>>
>>>>
>>>
>>>
>>> --
>>> What most experimenters take for granted before they begin their
>>> experiments is infinitely more interesting than any results to which their
>>> experiments lead.
>>> -- Norbert Wiener
>>>
>>
>>
>
>
> --
> What most experimenters take for granted before they begin their
> experiments is infinitely more interesting than any results to which their
> experiments lead.
> -- Norbert Wiener
>
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