[gradsusr] Set cache

[Jennifer M Adams]

Hi, Emily — 
The default cachesize is designed to hold one global 2D grid (Xsize*Ysize*8). Since your data set has large chunks (Xsize*Ysize*Zsize), I would suggest one of these two options (but not both):
1. set cachesf 100
2. put 'cachesize 9551808000’ in your descriptor file
Option #1 is more general, it applies to all chunked data sets you are using; option #2 is specific for each data set. You want the cache to be big enough to hold at least 2 chunks of data — more room to keep chunks in memory is better but you have to be careful not to use up all the available memory on your system, especially if it is a shared resource. Make sure that the system you’re working on has plenty of memory to support such a large cache. Add another zero to those numbers if you can. 

Best option is to tell whoever created the file you’re trying to read that they are using chunking in the worst possible way for use with GrADS. Chunks should be used to *divide* large grids into smaller pieces. 

What are the dimension environment settings when drawing a curtain plot? 
—Jennifer


> On Jul 30, 2018, at 10:40 AM, Saunders, Emily (GSFC-610.0)[SCIENCE SYSTEMS AND APPLICATIONS INC] <emily.saunders at nasa.gov> wrote:
> 
> Hi All,
> 
> I am trying to create a curtain plot of Ozone as a function of pressure, but I am using a rather large data set that include over 700 time steps. When I try to make the plot I receive the following error message from GrADs:
> 
> *** WARNING! ***
> *** The I/O for this variable will be extremely slow
> *** because the chunks are too big to fit in the cache
> *** chunk size = 95518080 bytes  (1440 * 721 * 23 * 1 * 4 bytes)
> *** cache size = 0 bytes
> *** There are two ways to control the cache size:
> *** add a CACHESIZE entry to the descriptor file
> *** or change the cache size scale factor with 'set cachesf'
> 
> I would like to know what value I should use for 'set cachesf' in my GrADs script or how to format the CACHESIZE entry in my descriptor file. Thank you for your help in advance.
> 
> -- 
> Emily Saunders, PhD.
> Senior Research Scientist
> Global Modeling and Assimilation Office/SSAI
> NASA Goddard Space Flight Center Bldg 33, Room H-111B
> Code 610.1, Greenbelt, MD, 20771
> Phone: +1-301-614-6532
> 
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--
Jennifer Miletta Adams
Center for Ocean-Land-Atmosphere Studies (COLA)
George Mason University