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<p class="MsoNormal"><span lang="PT">Hi Even,<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="PT"><o:p> </o:p></span></p>
<p class="MsoNormal">New Year, new mysteries. I’m having quite strange slow times in computing the min/max of netCDF files.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">In GMT we can read files via GDAL by appending =gd to the file name. So both of these do a similar job<o:p></o:p></p>
<p class="MsoNormal"><span lang="PT">grdinfo grav_29_img.nc=gd<o:p></o:p></span></p>
<p class="MsoNormal">and<o:p></o:p></p>
<p class="MsoNormal">gdalinfo grav_29_img.nc -mm<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">and it takes around 28 sec in a new laptop running Windows and master GDAL. However in WSL, same laptop but GDAL 2.2.3, they take about 5:30 MINUTES to run. On a OSX it takes about 3:30 minutes (not me who run this, and a GDAL 3.0.3 MacPorts)<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">On Windows for files of similar size it run faster when data is of type float (the grid in this example is a short int).<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Now, perhaps the weirdest thing is that if I run the GMT command via our Julia wrapper it only takes ~8 sec, whilst the same command via the Matlab wrapper took 1:18 min<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">The ~8 sec time is close to what I get with a pure GMT (i.e. not using GDAL to read the nc file (grdinfo grav_29_img.nc -M))<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">From the GMT side all happens in the call<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"> GDALComputeRasterMinMax(hBand, false, adfMinMax);<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">And I guess that the same holds from the pure GDAL call.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">If you want to test with the grid used in these testings, it’s here<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:10.0pt;font-family:"Helvetica",sans-serif"><a href="ftp://ftp.soest.hawaii.edu.pwessel">ftp://ftp.soest.hawaii.edu</a>/pwessel/<a href="http://grav_29_img.nc">grav_29_img.nc</a><o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Happy new year<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Joaquim<o:p></o:p></p>
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