<div dir="ltr">Hi Cameron,<div class="gmail_extra"><br><div class="gmail_quote">On Mon, May 2, 2016 at 7:21 PM, Cameron Hummels <span dir="ltr"><<a href="mailto:chummels@gmail.com" target="_blank">chummels@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-style:solid;border-left-color:rgb(204,204,204);padding-left:1ex"><div dir="ltr">I wasn't entirely objecting to punting it, but I think it warrants discussion here. Until I tried to build some Off axis projections and VRs for SPH data, I didn't realize that they weren't supported. In fact, which frontends are actually supported for doing VRs and OffAxisProjections? If Octtree-based code isn't, then that knocks out ART, ARTIO, and Ramses, and without SPH, it knocks out Gadget, Tipsy, Gizmo, and Gasoline, which leaves Enzo, Flash, and Athena? Others?<div><br></div><div>I honestly don't have any idea how much work it would take to construct a KDTree from octree data. I figured this was in the realm of CS and would probably have been solved elsewhere, but maybe not.</div></div></blockquote><div><br></div><div>Yes, it absolutely has. When you asked me about this over private message or public message on Slack a while back (I forget which) I sent back information about how to do this. I think it would be relatively straightforward to implement. You need to insert a couple "fake" levels in the octree so that it is a BSP rather than the way it functions now, but these cutting planes can be inserted at the existing cell refinement divisions. It would also be straightforward to implement a ray traversal that natively worked with Octrees, which would only require mocking PartitionedGrid objects and sorting the octs in the right order for the traversal. (This would result in an identical operation, I think.)</div><div><br></div><div><div>My understanding is that when over_refine_factor > 1, it works for particle data sets. Desika had success with this. I may no longer be right.</div></div><div><br></div><div>Even without any new development, I have not heard of anyone attempting to debug why and where the segfault occurs. My suspicion is that it's a fencepost error that shows up because of the binary division in the octree. That would be a good first place to look.</div><div> </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-style:solid;border-left-color:rgb(204,204,204);padding-left:1ex"><div dir="ltr"><div><br></div><div>Anyway, I'm not trying to be too obstructionist here, just trying to have a discussion, since there were at least 4 other issues filed regarding this in the past, so it seems relevant for a lot of users.</div></div></blockquote><div><br></div><div>I think this would be a great use of resources, but I don't think it should block 3.3. I do not know when I would be able to devote the time to it; if someone else is willing to volunteer that time, I think it would be great. Would you be willing to put the time in to ensure that it could happen? If so, I think making it a blocker on 3.3 and setting a deadline for it would be a good compromise; if it isn't done by that deadline, punt until the next release.</div><div><br></div><div>-Matt</div><div> </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-style:solid;border-left-color:rgb(204,204,204);padding-left:1ex"><div dir="ltr"><div><br></div><div>Cameron</div></div><div class="gmail_extra"><br><div class="gmail_quote"><div><div class="h5">On Mon, May 2, 2016 at 4:26 PM, Nathan Goldbaum <span dir="ltr"><<a href="mailto:nathan12343@gmail.com" target="_blank">nathan12343@gmail.com</a>></span> wrote:<br></div></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-style:solid;border-left-color:rgb(204,204,204);padding-left:1ex"><div><div class="h5"><div dir="ltr">Hi all,<div><br></div><div>I'm moving some discussion from the comments in issue #1212 over to the mailing list:</div><div><br></div><div><a href="https://bitbucket.org/yt_analysis/yt/issues/1212" target="_blank">https://bitbucket.org/yt_analysis/yt/issues/1212</a><br></div><div><br></div><div>I wanted to check with the list since Cameron objected a bit in the issue discussion.<br></div><div><br></div><div>The issue Cameron identifies is pretty serious, but fully fixing it will require pretty substantial work - adding support for octree data to the AMRKDTree.</div><div><br></div><div>I've gone ahead and marked it for version 3.4 - i.e. that it shouldn't be a blocker for the 3.3 release. I've also created issue 1215:</div><div><br></div><div><a href="https://bitbucket.org/yt_analysis/yt/issues/1215" target="_blank">https://bitbucket.org/yt_analysis/yt/issues/1215</a><br></div><div><br></div><div>which will be fixed when yt produces a useful error message rather than seg faulting when trying to construct an AMRKDTree for unsupported data.</div><div><br></div><div>I think that requiring someone to add support for octree data to the AMRKDTree before we release 3.3 is effectively delaying the 3.3 release arbitrarily far into the future, since no one is currently willing to work on that project. That would be unfortunate, because there's lots of cool stuff people have worked on that deserves a stable release.</div><span><font color="#888888"><div><br></div><div>-Nathan</div></font></span></div>
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<br></span></blockquote></div><span class=""><font color="#888888"><br><br clear="all"><div><br></div>-- <br><div><div dir="ltr"><div>Cameron Hummels<div><span style="font-size:12.8px">NSF Postdoctoral Fellow</span></div><div><span style="font-size:12.8px">Department of Astronomy</span></div><div><span style="font-size:12.8px">California Institute of Technology</span><br></div><div><a href="http://chummels.org" style="font-size:12.8px" target="_blank">http://chummels.org</a><br></div></div></div></div>
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