Parallel Netcdf Feature

[Yu-Heng Tseng]

Jianwei,

Thanks for your explanation.
Do I really need to use MPI subarray datatype?
I attempted to use subarray function put_vara_*
It seems I couldn't get what I want.

Do you have any test example to verify this function?
I tested it using the test code in test/fandc/pnf_test.F

For example, ARRAY has dimension (4,3), e.g.
    ARRAY=[ 1, 2, 3,
            5, 6, 7,
            9,10,11,
           13,14,15]
So ARRAY(1,1)=1; ARRAY(1,2)=2; ARRAY(1,3)=3;
   ARRAY(2,1)=5; ARRAY(2,2)=6;

If I use two processes to output by using nfmpi_put_vara()
setting start()=[1,1],count()=[3,2] for process 0
Process 0 outputs
1,2,3,
5,6,7,             

setting start()=[1,3],count()=[3,2] for process 1
process 1 outputs
9,10,11,
13,14,15

So I use "ncdump pnf_test.nc" and get
 1, 2, 3,
 5, 6, 7,
 9,10,11,
13,14,15
This looks fine to output the whole array.
However, when I modify start() and count() as you suggested
to output only part of the subarray, I didn't get what I want.
In process 0, I set start()=[1,2], count()=[3,1] (ignore 1st row)
In process 1, I set start()=[1,3], count()=[3,2] (the same)

It gives me
 0, 0, 0,
 1, 2, 3,
 9,10,11,
13,14,15

It appears that the output always starts from
the first element rather than the starting location I specify
from the start(). Am I doing something wrong?
My objective is to output 
 5, 6, 7,
 9,10,11,
13,14,15
(ignore 1st row)

But I don't think it can work for parallel netCDF.
It will be great if you can provide any example. Thanks!

Yu-heng

----- Original Message -----
From: Jianwei Li <jianwei at ece.northwestern.edu>
Date: Monday, June 20, 2005 8:53 am
Subject: Re: Parallel Netcdf Feature

> 
> Yu-heng,
> 
> I did not quite catch what you want, but basically
> our subarray functions put/get_vara can exclude
> boundary columns/rows as many as you want to.
> You just need to specify start[] and count[] vectors
> for the subarray, e.g., process 0 can specify
> start[] = {0, 1} and count[] = {3, 1} while process 1
> can specify start[] = {0, 2} and count[] = {3, 2}.
> 
> Thanks,
> Jianwei
> 
> On Sun, 19 Jun 2005, Yu-Heng Tseng wrote:
> 
> > Hi
> >
> > I am interested in doing some complicated output
> > using parallel NETCDF so that each process outputs
> > different sizes.
> > For example, the total size has two dimensions (x,y).
> > If the total size is (4,3), e.g.
> >
> > 1,2,3,4,
> > 5,6,7,8
> > 9,10,11,12
> >
> > If we use two processes:
> > Process 0 has  and process 1 has
> > 1,2,               3,4,
> > 5,6,               7,8,
> > 9,10               11,12
> > I don't want to output the first column
> > (which includes 1,5,9). How can I output
> > the rest 9 variables
> > 2,3,4,
> > 6,7,8,
> > 10,11,12
> >
> > Can I obtain some examples? or can someone
> > tell me any particular subroutine I can use?
> > I can check it out. There are not many test
> > examples in the current release.
> > Thank you very much.
> >
> > Yu-heng
> >
> 
> 
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