[petsc-users] RAW binary write

[Lisandro Dalcin]

PetscByteSwap ? But be careful, you should (1) vec get array, byteswap, vec
restore array, (2) view, (3) vec get array, byteswap, vec restore array. Of
course, if you do not care about the final Vec contents, you can just omit
step (3) and let it be, let it be...

PS: Eventually, PETSc binary viewers should gain an API like
PetscViewerBinarySetByteOrder(viewer, PETSC_LITTLE_ENDIAN) ...

On Tue, 4 Dec 2018 at 12:33, Sal Am <tempohoper at gmail.com> wrote:

> Thank you so much Lisandro!
>
> That was very helpful actually and what I was looking for, but now it
> still requires an intermediate step of a short python script where I have
> to use byteswap() on the data to get it to work on other platforms.
> Would you happen to know any way of byteswapping in petsc? I was reading
> and it seems PetscBinaryWrite does byteswapping but I am not sure it would
> work in my case as there are no examples with it writing a petsc vector.
>
> Thanks and all the best
>
> On Sun, Dec 2, 2018 at 10:01 AM Lisandro Dalcin <dalcinl at gmail.com> wrote:
>
>> Use PetscViewerBinarySetSkipHeader(viewer, PETSC_TRUE) before VecView().
>>
>> On Thu, 29 Nov 2018 at 18:50, Sal Am via petsc-users <
>> petsc-users at mcs.anl.gov> wrote:
>>
>>> Is there a way to write the solution from the system Ax=b in raw binary
>>> instead of PETSc binary format?
>>>
>>> Currently I am doing:
>>>   ierr = PetscViewerBinaryOpen(PETSC_COMM_WORLD,
>>> "../../python/petscpy/Vector_x_petsc.dat", FILE_MODE_WRITE,
>>> &viewer);CHKERRQ(ierr);
>>>   ierr = VecView(x,viewer);CHKERRQ(ierr);CHKERRQ(ierr);
>>>   ierr = PetscViewerDestroy(&viewer);CHKERRQ(ierr);
>>>
>>> And then use PetscBinaryIO to read it back and save it using
>>> write('newformat', 'wb') to get to raw... however this approach is not good
>>> it seems as there are some troubles with little/big endian when using the
>>> resulting converted file on other systems for post-processing.
>>>
>>> Thanks,
>>>
>>
>>
>> --
>> Lisandro Dalcin
>> ============
>> Research Scientist
>> Computer, Electrical and Mathematical Sciences & Engineering (CEMSE)
>> Extreme Computing Research Center (ECRC)
>> King Abdullah University of Science and Technology (KAUST)
>> http://ecrc.kaust.edu.sa/
>>
>> 4700 King Abdullah University of Science and Technology
>> al-Khawarizmi Bldg (Bldg 1), Office # 0109
>> Thuwal 23955-6900, Kingdom of Saudi Arabia
>> http://www.kaust.edu.sa
>>
>> Office Phone: +966 12 808-0459
>>
>

-- 
Lisandro Dalcin
============
Research Scientist
Computer, Electrical and Mathematical Sciences & Engineering (CEMSE)
Extreme Computing Research Center (ECRC)
King Abdullah University of Science and Technology (KAUST)
http://ecrc.kaust.edu.sa/

4700 King Abdullah University of Science and Technology
al-Khawarizmi Bldg (Bldg 1), Office # 0109
Thuwal 23955-6900, Kingdom of Saudi Arabia
http://www.kaust.edu.sa

Office Phone: +966 12 808-0459
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