<div>Sorry, you're using terminology I'm unfamiliar with. Are passive particles the same thing as tracer particles? If so I agree they should probably be considered separately from n-body particles. For the derived quantities that motivated this example, massless particles would also need to be neglected.</div><div><br><div class="gmail_quote"><div>On Wed, Mar 29, 2017 at 5:40 PM Michael Zingale <<a href="mailto:michael.zingale@stonybrook.edu">michael.zingale@stonybrook.edu</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div class="gmail_msg">I think the name n-body only makes sense for datasets with active particles, not those with passive particles. The latter are the ones that I typically deal with. So maybe a different name? or maybe a way for a code to register if it is using active or passive particles?</div><div class="gmail_extra gmail_msg"></div><div class="gmail_extra gmail_msg"><br class="gmail_msg"><div class="gmail_quote gmail_msg">On Wed, Mar 29, 2017 at 5:36 PM, Nathan Goldbaum <span class="gmail_msg"><<a href="mailto:nathan12343@gmail.com" class="gmail_msg" target="_blank">nathan12343@gmail.com</a>></span> wrote:<br class="gmail_msg"><blockquote class="gmail_quote gmail_msg" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div class="gmail_msg"><br class="gmail_msg"><div class="gmail_extra gmail_msg"><br class="gmail_msg"><div class="gmail_quote gmail_msg"><span class="gmail_msg">On Wed, Mar 29, 2017 at 4:33 PM, Cameron Hummels <span class="gmail_msg"><<a href="mailto:chummels@gmail.com" class="gmail_msg" target="_blank">chummels@gmail.com</a>></span> wrote:<br class="gmail_msg"><blockquote class="gmail_quote gmail_msg" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div class="gmail_msg">Wait, so we'd have both an 'all' ftype and an 'n-body' ftype and the 'n-body' ftype would just include non-gas particles (ie ones without the 'smoothing_length' field)? I'm assuming this won't add more computational load when reading in the dataset? </div></blockquote><div class="gmail_msg"><br class="gmail_msg"></div></span><div class="gmail_msg">I doubt it. There will just be some more fields in ds.derived_field_list (one 'n-body' field for each of the 'all' fields).</div><div class="gmail_msg"><div class="m_1484161905926588015h5 gmail_msg"><div class="gmail_msg"> </div><blockquote class="gmail_quote gmail_msg" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div class="gmail_msg">If that's the case, then I'm +0.5 on it. I haven't had a need for it up to this point, but maybe other people really need it?</div><div class="gmail_extra gmail_msg"><div class="gmail_msg"><div class="m_1484161905926588015m_-3853963773584262031h5 gmail_msg"><br class="gmail_msg"><div class="gmail_quote gmail_msg">On Wed, Mar 29, 2017 at 2:21 PM, John ZuHone <span class="gmail_msg"><<a href="mailto:jzuhone@gmail.com" class="gmail_msg" target="_blank">jzuhone@gmail.com</a>></span> wrote:<br class="gmail_msg"><blockquote class="gmail_quote gmail_msg" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div style="word-wrap:break-word" class="gmail_msg">+1.<div class="gmail_msg"><br class="gmail_msg"></div><div class="gmail_msg">"n_body"?</div><div class="gmail_msg"><div class="m_1484161905926588015m_-3853963773584262031m_3168107345220518545h5 gmail_msg"><div class="gmail_msg"><br class="gmail_msg"></div><div class="gmail_msg"><div class="gmail_msg"><blockquote type="cite" class="gmail_msg"><div class="gmail_msg">On Mar 29, 2017, at 5:19 PM, Matthew Turk <<a href="mailto:matthewturk@gmail.com" class="gmail_msg" target="_blank">matthewturk@gmail.com</a>> wrote:</div><br class="m_1484161905926588015m_-3853963773584262031m_3168107345220518545m_-5319955312075545618Apple-interchange-newline gmail_msg"><div class="gmail_msg"><div class="gmail_msg">+1, and I think updating YTEP-0031 is sufficient. Not sure that "n-body" specifically is my preference, since it's not tokenizable, but maybe it's fine.</div><div class="gmail_extra gmail_msg"><br class="gmail_msg"><div class="gmail_quote gmail_msg">On Wed, Mar 29, 2017 at 4:18 PM, Nathan Goldbaum <span class="gmail_msg"><<a href="mailto:nathan12343@gmail.com" class="gmail_msg" target="_blank">nathan12343@gmail.com</a>></span> wrote:<br class="gmail_msg"><blockquote class="gmail_quote gmail_msg" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div class="gmail_msg">Hi all,<div class="gmail_msg"><br class="gmail_msg"></div><div class="gmail_msg">I'd like to propose adding a new particle union that should be defined for all datasets that include particles. This came up in the context of the demeshening work (see <a href="https://bitbucket.org/yt_analysis/ytep/pull-requests/67" class="gmail_msg" target="_blank">https://bitbucket.org/yt_analysis/ytep/pull-requests/67</a> for more details).</div><div class="gmail_msg"><br class="gmail_msg"></div><div class="gmail_msg">Right now many of the derived quantities make a distinction between calculating results using just the gas or just the particles or both. Up until now they have calculated the results for particles using particle fields from the 'all' particle union. This makes perfect sense for AMR data but doesn't really make sense for SPH data, since it will double-count SPH particles. In fact, I think this is an issue even without the demeshening, but the demeshening makes it more starkly apparent.</div><div class="gmail_msg"><br class="gmail_msg"></div><div class="gmail_msg">I'd like to propose defining a new "n-body" particle union (suggestions for alternate names are very welcome) that will be defined for all yt datasets. This union will be identical to the 'all' particle union for AMR data and N-body particle data, but for SPH data will only include the particle types that aren't SPH particles (if any). That means the "n-body" particle type represents infinitesimal particles but not particles that have finite extents (e.g. an SPH particle's smoothing region).</div><div class="gmail_msg"><br class="gmail_msg"></div><div class="gmail_msg">I think this new particle type would probably be generically useful beyond just the derived quantities, maybe even more useful than "all". I also kind of prefer the name "n-body" to "all" since it more prominently indicates that it's associated with particle data.</div><div class="gmail_msg"><br class="gmail_msg"></div><div class="gmail_msg">Please let me know if you have thoughts or suggestions about this proposal. I'm happy to draft a YTEP or update YTEP-0031 with more details if people want to see that.</div><span class="m_1484161905926588015m_-3853963773584262031m_3168107345220518545m_-5319955312075545618HOEnZb gmail_msg"><font color="#888888" class="gmail_msg"><div class="gmail_msg"><br class="gmail_msg"></div><div class="gmail_msg">-Nathan</div></font></span></div>
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<br class="gmail_msg"></blockquote></div><br class="gmail_msg"><br clear="all" class="gmail_msg"><div class="gmail_msg"><br class="gmail_msg"></div></div></div><span class="m_1484161905926588015m_-3853963773584262031HOEnZb gmail_msg"><font color="#888888" class="gmail_msg">-- <br class="gmail_msg"><div class="m_1484161905926588015m_-3853963773584262031m_3168107345220518545gmail_signature gmail_msg" data-smartmail="gmail_signature"><div class="gmail_msg"><div class="gmail_msg">Cameron Hummels<div class="gmail_msg"><span style="font-size:12.8000001907349px" class="gmail_msg">NSF Postdoctoral Fellow</span></div><div class="gmail_msg"><span style="font-size:12.8000001907349px" class="gmail_msg">Department of Astronomy</span></div><div class="gmail_msg"><span style="font-size:12.8000001907349px" class="gmail_msg">California Institute of Technology</span><br class="gmail_msg"></div><div class="gmail_msg"><a href="http://chummels.org" style="font-size:12.8000001907349px" class="gmail_msg" target="_blank">http://chummels.org</a><br class="gmail_msg"></div></div></div></div>
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<br class="gmail_msg"></blockquote></div><br class="gmail_msg"><br clear="all" class="gmail_msg"><div class="gmail_msg"><br class="gmail_msg"></div>-- <br class="gmail_msg"></div><div class="gmail_extra gmail_msg"><div class="m_1484161905926588015gmail_signature gmail_msg" data-smartmail="gmail_signature"><div class="gmail_msg"><div class="gmail_msg"><div class="gmail_msg">Michael Zingale</div><div class="gmail_msg">Associate Professor</div><div class="gmail_msg"><br class="gmail_msg"></div><div class="gmail_msg">Dept. of Physics & Astronomy • Stony Brook University • Stony Brook, NY 11794-3800</div><div class="gmail_msg"><i class="gmail_msg">phone</i>: 631-632-8225</div><div class="gmail_msg"><i class="gmail_msg">e-mail</i>: <a href="mailto:Michael.Zingale@stonybrook.edu" class="gmail_msg" target="_blank">Michael.Zingale@stonybrook.edu</a></div><div class="gmail_msg"><i class="gmail_msg">web</i>: <a href="http://www.astro.sunysb.edu/mzingale" class="gmail_msg" target="_blank">http://www.astro.sunysb.edu/mzingale</a></div><div class="gmail_msg">github: <a href="http://github.com/zingale" class="gmail_msg" target="_blank">http://github.com/zingale</a></div><div class="gmail_msg"><br class="gmail_msg"></div></div></div></div>
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