[gradsusr] Problem: extracting a variable from a big file

[Jennifer Adams]

Whenever you submit a question, it is impossible to answer without  
knowing two things: the version of GrADS you are running, and the  
platform you are running it on. THIS REALLY MATTERS!

Your 'subset' file should be 10242422568 bytes (399*279*31*742*4)
If it is not, then you can blame mm5_to_grads.sh -- maybe it doesn't  
have the capability to write out a 9.5Gb file... Try breaking up your  
output into 742 separate files and template them together with GrADS.

The error messages you're getting indicate that GrADS is having  
trouble moving to the correct position in the file to fulfill your I/O  
request. Older versions of GrADS did not have the capability to read  
files > 2GB, but who can tell whether this is your problem because you  
didn't provide enough information about your GrADS build.

--Jennifer


On Nov 18, 2010, at 8:42 AM, Matias Mendez wrote:

> Dear GrADS users,
>
> I have a big MM5 output (~100GB, with 31 sigma-levels, 742 hourly time
> steps, 23 variables). I have used mm5_to_grads.sh to extract a
> variable (u-wind). After that I tried to display this variable,
> everything  was working fine but when I did:
>
> d u(t=623)
>
> I got the following error mesage:
>
> Notice:  Automatic Grid Interpolation Taking Place
> Low Level I/O Error:  Seek error on data file
>  Data file name = /home/XXXXX/U_ENE-2006.dat
> 523 rc=-1 fpos=-2145136144 pfi->fhdr=-1
>  Error occurred when seeking to byte 9390016
> Data Request Error:  Error for variable 'u'
>  Error ocurred at column 1
> DISPLAY error:  Invalid expression
>  Expression = u(t=623)
>
> What does this mean this message and how can I solve this problem?.
> Is there another way to extract a variable from a big file?. Any
> sugesstion is welcome. Thanks in advance.
>
> Best regards,
> Matías
>
> P.S.
> This is the ctl file created by mm5_to_grads.sh
>
> dset /home/XXXXX/U_ENE-2006.dat
> byteswapped
> title MM5 data
> undef -9999.
> pdef  399  279 lcc   24.00 -102.00  200.00  140.00   30.00   60.00  
> -102.00   900
> 0.   9000.
> xdef  972 linear -121.69  0.0405
> ydef  571 linear   12.15  0.0405
> zdef  31 levels
> 0.99950
> 0.99800
> 0.99600
> 0.99400
> 0.99200
> 0.98950
> 0.98700
> 0.98500
> 0.98300
> 0.98100
> 0.97500
> 0.96000
> 0.94000
> 0.92000
> 0.90500
> 0.89000
> 0.87000
> 0.85000
> 0.83000
> 0.81000
> 0.79000
> 0.76000
> 0.72000
> 0.68000
> 0.64000
> 0.61000
> 0.55000
> 0.45000
> 0.35000
> 0.20000
> 0.05000
> tdef 742 linear 00:00Z01JAN2006   60MN
> vars  1
> u         31 99 u wind (m/s)
> endvars
>
> _______________________________________________
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--
Jennifer M. Adams
IGES/COLA
4041 Powder Mill Road, Suite 302
Calverton, MD 20705
jma at cola.iges.org



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