<html><head><meta http-equiv="Content-Type" content="text/html charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class="">Hi Nilou,<div class=""><br class=""></div><div class="">I’m not 100% sure, but I think there are a few reasons why you are seeing this behavior. First, I’m not even sure that collectiveIO works with uniform grid mode. The collective aspect means that blocks are collected on a subset of ranks before being written to disk. In UG, there is only one block per rank by construction…so I’m just not sure it works together. </div><div class=""><br class=""></div><div class="">Second, collectiveIO is to overcome issues in parallel writes of contention amongst many ranks attempting to write to a single file. In my experience, this only matters when the number of ranks is in the 1000s or more. I don’t think your problem size is anywhere near large enough to see a benefit from collective IO.</div><div class=""><br class=""></div><div class="">Sean</div><div class=""><br class=""></div><div class=""><br class=""><div class="">
<div style="color: rgb(0, 0, 0); letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div style="color: rgb(0, 0, 0); letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div style="color: rgb(0, 0, 0); letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class="">-----------------------------------------------------------<br class="">Sean M. Couch<br class="">Theoretical Astrophysics Including Relativity<br class="">California Institute of Technology<br class="">Mail Code 350-17<br class="">Pasadena, CA 91125<br class="">(626) 395-4282<br class=""><a href="http://www.tapir.caltech.edu/~smc" class="">www.tapir.caltech.edu/~smc</a></div></div></div>
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<br class=""><div><blockquote type="cite" class=""><div class="">On Mar 8, 2015, at 6:10 PM, niloofar afsari <<a href="mailto:nlr_afsari@yahoo.com" class="">nlr_afsari@yahoo.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div class=""><div style="background-color: rgb(255, 255, 255); font-family: HelveticaNeue, 'Helvetica Neue', Helvetica, Arial, 'Lucida Grande', sans-serif; font-size: 16px;" class=""><div id="yui_3_16_0_1_1425861570983_6485" dir="ltr" class="">Hi Flash users,</div><div id="yui_3_16_0_1_1425861570983_6485" dir="ltr" class=""><br class=""></div><div id="yui_3_16_0_1_1425861570983_6485" dir="ltr" class="">I'm running a 2d Sedov explosion (I've changed it to be compatible with spherical coordinates) simulation in a spherical coordinates on a uniform grid:</div><div id="yui_3_16_0_1_1425861570983_6485" dir="ltr" class=""> </div><div id="yui_3_16_0_1_1425861570983_6485" dir="ltr" class="">./setup Sedov -auto +ug +parallelIO -2d -nxb=1024 -nyb=1024</div><div id="yui_3_16_0_1_1425861570983_6485" dir="ltr" class=""><br class=""></div><div id="yui_3_16_0_1_1425861570983_6485" dir="ltr" class="">In flash.par, I've set the "useCollectiveHDF5" to true. </div><div id="yui_3_16_0_1_1425861570983_6485" dir="ltr" class=""><br class=""></div><div id="yui_3_16_0_1_1425861570983_6485" dir="ltr" class="">So far, I've changed nxb=nyb in the range [128, 2048] and iProcs=jProcs in the range [1,3].</div><div id="yui_3_16_0_1_1425861570983_6485" dir="ltr" class=""><br class=""></div><div id="yui_3_16_0_1_1425861570983_6485" dir="ltr" class="">I've never seen any speed-up when running my simulation with -np higher than 1. I'm wondering if this is expected or I'm missing an important speed-up flash/option.</div><div id="yui_3_16_0_1_1425861570983_6485" dir="ltr" class=""><br class=""></div><div id="yui_3_16_0_1_1425861570983_6485" dir="ltr" class="">Thank you for your help!</div><div id="yui_3_16_0_1_1425861570983_6485" dir="ltr" class=""><br class=""></div><div id="yui_3_16_0_1_1425861570983_6485" dir="ltr" class="">Nilou</div><div id="yui_3_16_0_1_1425861570983_6485" dir="ltr" class=""><br class=""></div></div></div></div></blockquote></div><br class=""></div></body></html>