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Hi, Jim —
<div>The data I/O is slow with ‘define’ command because define always loops over T under the hood and is therefore getting one data value at a time. Actually, this is the way GrADS does I/O in general (row by row), but your example meets the requirements for
a special case I/O request: netcdf, no pdef, not templated, and no offt. In this special case, a ‘display’ request will get all times in one I/O ping to the server, but with ‘define’ it will always loop over T. Using a server-side analysis request will mean
that the 1000 data points will sit in the server’s cache, and if you make this request more than once the I/O will not be repeated on the server side, so your repeated ‘display’ requests may be a bit faster. Something like this:</div>
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<div>'sdfopen <a href="http://monsoondata.org:9090/dods/precip/_expr_{precip}{anal}{put.your.world.coordinate.dimension.limits.here}'">
http://monsoondata.org:9090/dods/precip/_expr_{precip}{anal}{put.your.world.coordinate.dimension.limits.here}'</a></div>
<div>‘d result’</div>
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<div>—Jennifer</div>
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<div>On Aug 8, 2016, at 11:32 PM, James T. Potemra <<a href="mailto:jimp@hawaii.edu">jimp@hawaii.edu</a>> wrote:</div>
<br class="Apple-interchange-newline">
<blockquote type="cite">Hi all,<br>
<br>
I'm trying to access a single lat/lon point from a gridded file. I <br>
noticed that displaying the output is very fast (order seconds), while <br>
if I try and define a variable, the response is very slow (order several <br>
minutes).<br>
<br>
As an example, the TRMM precip at the monsoondata server is dimensioned <br>
lat/lon/time. Below, I extract 1000 time points at 20N, 158W. The <br>
following displays this time-series and completes in about 5 seconds:<br>
<br>
sdfopen <a href="http://www.monsoondata.org:9090/dods/precip'">http://www.monsoondata.org:9090/dods/precip'</a><br>
set lat 20<br>
set lon 202<br>
set t 1 1000<br>
d anal<br>
<br>
On the other hand, trying to save this as a variable takes about 4 minutes:<br>
<br>
sdfopen <a href="http://www.monsoondata.org:9090/dods/precip">http://www.monsoondata.org:9090/dods/precip</a><br>
set lat 20<br>
set lon 202<br>
set t 1 1000<br>
define rain=anal<br>
<br>
I'm wondering if there is a server-side constraint I can use to speed <br>
this up? Although I suspect this is not really a server issue since <br>
I've tried a few different servers and datasets/variables with similar <br>
results (and the display works quickly). Alternately maybe there is a <br>
way to more efficiently define a 1D variable? Thanks in advance,<br>
<br>
Jim<br>
<br>
Using Config: v2.1.a2 little-endian readline grib2 netcdf hdf4-sds hdf5 <br>
opendap-grids,stn geotiff shapefile cairo<br>
<br>
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</blockquote>
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<div style="font-size: 12px; orphans: 2; widows: 2;">--</div>
<div style="font-size: 12px; orphans: 2; widows: 2;">Jennifer Miletta Adams<br>
Center for Ocean-Land-Atmosphere Studies (COLA)<br>
George Mason University<br>
<br>
<br>
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