[MITgcm-support] Forcing dataset check

[Martin Losch]

Hi Jody,

I am not really the expert on this, but input files all need to be big endian, and so are the (mds) output files, independent of the endian-ness of your platform. Nowadays all (nearly all) compilers have a flag that converts to big endian somewhere internally. If you compiler does not have this flat, then you can use a _BYTESWAPIO flag in your build option file (see eg. linux_ia32_g77: DEFINES='-D_BYTESWAPIO -DWORDLENGTH=4 -DNML_EXTENDED_F77’). This flag turn one code (S/R MDS_BYTESWAPR4 or MDS_BYTESWAPR8) that does the conversion, and yes, I assume that there is a penalty, because this conversion is done every time a file is written or read.

Martin

> On 01 Jul 2015, at 09:43, Jody Klymak <jklymak at uvic.ca> wrote:
> 
> Hi Martin et al,
> 
> 
>> On Jul 1, 2015, at  8:40 AM, Martin Losch <Martin.Losch at awi.de> wrote:
>> 
>> (ieee-big endian unblocked, so that they can be opened in fortran with direct access) 
> 
> Off topic, but I keep hearing this.  Is this true if your underlying architecture is little-endian?  Is there some kind of performance penalty to little-endian i/o on an intel cluster?  
> 
> Thanks,   Jody
> 
> 
> 
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