[Nek5000-users] Reading binary data

Thu Aug 12 08:58:51 CDT 2010

Stefan,

Ok, I see all the contributions to the field file when mesh data is included.  The only thing I am still unsure of is the order of the components.  Can you please check the order in my list below and tell me what should be moved?

Field File with mesh data
============================
1) header: 132 bytes
2) endian test tag: 4 bytes
3) element mapping: nel* 4 bytes
4) mesh data:  nel * nx*ny*nz * ndim * wdsizo
5) field data: nfields*nxyz*nel* wdsizo (where wdsizo is 4 or 8 bytes)
6) field metadata (min/max values): nfields*2*nel * 4 bytes
7) mesh metadata: ndim*ne*2*4

Thanks again for all your help.

--Mike

________________________________________
From: nek5000-users-bounces at lists.mcs.anl.gov [nek5000-users-bounces at lists.mcs.anl.gov] On Behalf Of nek5000-users at lists.mcs.anl.gov [nek5000-users at lists.mcs.anl.gov]
Sent: Thursday, August 12, 2010 1:06 AM
To: nek5000-users at lists.mcs.anl.gov
Subject: Re: [Nek5000-users] Reading binary data

The 12288 bytes is the metadata for all 3 mesh coordinates:
ndim * nel * 2 * 4 bytes

Stefan

On Aug 12, 2010, at 12:21 AM, <nek5000-users at lists.mcs.anl.gov> wrote:

> Sorry -- I'm still not getting it.
>
> The first file had mesh coordinates and field information in it; here is what the header shows:
>
> #std 4  8  8  8        512        512  0.2000000000000E+02      1000      0      1 XUPS02
>
> The size of this file is  9476232, but I can't figure out what is contributing to that size.  For the next field file, the header shows:
>
> #std 4  8  8  8        512        512  0.1200000000000E+03      6000      0      1 UPS02
>
> The size of this file is 6318216, which is exactly predicted by the expression below -- all is well.
>
> What is the makeup of the 3158016 bytes difference between these files?  The mesh coordinates alone are only
>
> 512 * 8^3 * 4 * 3 (ndim) = 3145728 bytes
>
> Where and what are the remaining 12288 bytes?
>
> Thanks.
>
>
>
> On Aug 11, 2010, at 4:09 PM, <nek5000-users at lists.mcs.anl.gov> wrote:
>
>> No, if a field file only contains the geometry (mesh coordinates) nfields is equal to ndim (2 or 3).
>> Stefan
>>
>>
>> On Aug 12, 2010, at 12:01 AM, <nek5000-users at lists.mcs.anl.gov> wrote:
>>
>>> Stefan,
>>>
>>> Thanks.  I figured that, but the binary file size doesn't seem to be adding up.    For example,  a field file that doesn't have geometry data is the size described by the initial thread, i.e.
>>>
>>> 132 bytes + 4 bytes + nel* 4 bytes + nfields*nxyz*nel* wdsizo  +  nfields*2*nel * 4 bytes
>>>
>>> My naive assumption was that a field file with xyz data would then have the additional space requirement of
>>>
>>> nx*ny*nz*nel*wdsizo
>>>
>>> but the file's bigger than that.  What info am I missing?
>>>
>>> --Mike
>>>
>>> On Aug 11, 2010, at 3:50 PM, <nek5000-users at lists.mcs.anl.gov> wrote:
>>>
>>>> Hi Mike,
>>>>
>>>> vector fields (e.g. mesh coordinates) are stored in the following way:
>>>>
>>>> LOOP over all elements
>>>>    LOOP i = {x,y,z}
>>>>             i for all GLL points (internal element points)
>>>>    ENDLOOP
>>>> ENDLOOP
>>>>
>>>> 2D example with (E=2,N=2):
>>>> x1_1 x2_1 x3_1 y1_1 y2_1 y3_1 x1_1 x2_2 x3_2 y1_2 y2_2 y3_2
>>>>
>>>> where x2_1 means the x-coordinate of the 2nd GLL point of element 1.
>>>>
>>>> hth,
>>>> Stefan
>>>>
>>>> On Aug 11, 2010, at 11:34 PM, <nek5000-users at lists.mcs.anl.gov> wrote:
>>>>
>>>>>
>>>>> Hello All.  I found this helpful message from Stefan regarding the structure of a binary field file.   Could someone please tell me what the structure is when the geometry info is also contained?
>>>>>
>>>>> Thanks!
>>>>> --Mike
>>>>>
>>>>> nek5000-users at lists.mcs.anl.gov nek5000-users at lists.mcs.anl.gov
>>>>>> Thu May 6 07:18:03 CDT 2010
>>>>>>  • Previous message: [Nek5000-users] Reading binary data
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>>>>>> Hi Fred,
>>>>>>
>>>>>> header: 132 bytes
>>>>>> endian test tag: 4 bytes
>>>>>> element mapping: nel* 4 bytes
>>>>>> data: nfields*nxyz*nel* wdsizo (where wdsizo is 4 or 8 bytes)
>>>>>> metadata (min/max values): nfields*2*nel * 4 bytes
>>>>>>
>>>>>> Stefan
>>>>>>
>>>>>
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