<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="">This is definitely a bug and I have run into it before as well.<div class=""><br class=""></div><div class="">I’ll have a look for you, as I happen to have a ramses non-cosmological run at hand to test on.</div><div class=""><br class=""></div><div class="">Ricarda</div><div class=""><br class=""><div><blockquote type="cite" class=""><div class="">On 5 Jun 2015, at 00:28, Desika Narayanan <<a href="mailto:dnarayan@haverford.edu" class="">dnarayan@haverford.edu</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><meta http-equiv="Content-Type" content="text/html; charset=utf-8" class=""><div dir="ltr" class="">Hey All - thanks for this - the PR was useful to look at to get a sense of the history of the issue. <div class=""><br class=""></div><div class="">The data set is an idealized disk. Though because this is an Agora snapshot, I'm surprised this hasn't been noticed by someone else before. (It's not mine - I got a set of them from Mike Butler and Oscar Agertz for testing my radiative transfer code).</div><div class=""><br class=""></div><div class="">Ben - I just shot an email to see if it's okay for me to share the snapshot (I assume it probably is) which might help comparison with pymses. </div><div class="">thanks!</div><div class="">-d</div></div><div class="gmail_extra"><br class=""><div class="gmail_quote">On Thu, Jun 4, 2015 at 6:18 PM, Nathan Goldbaum <span dir="ltr" class=""><<a href="mailto:nathan12343@gmail.com" target="_blank" class="">nathan12343@gmail.com</a>></span> wrote:<br class=""><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr" class="">This was last touched back in December:<div class=""><br class=""></div><div class=""><a href="https://bitbucket.org/yt_analysis/yt/pull-request/1335/ramses-unit-conversions/diff" target="_blank" class="">https://bitbucket.org/yt_analysis/yt/pull-request/1335/ramses-unit-conversions/diff</a><br class=""></div><div class=""><a href="https://bitbucket.org/yt_analysis/yt/issue/939/units-error-in-ramses-frontend" target="_blank" class="">https://bitbucket.org/yt_analysis/yt/issue/939/units-error-in-ramses-frontend</a><br class=""></div><div class=""><br class=""></div><div class="">when I updated this, I attempted to set the units in exactly the same way as pymses. Unfortunately since I'm not a ramses user and don't have access to a diversity of test datasets, it's hard to get this exactly right in all cases.</div><div class=""><br class=""></div><div class="">Is your dataset cosmological? I wouldn't be surprised if there are subtle differences in the way units are set up for comoving and non-comoving simulations.</div></div><div class="gmail_extra"><br class=""><div class="gmail_quote"><div class=""><div class="h5">On Thu, Jun 4, 2015 at 2:59 PM, Desika Narayanan <span dir="ltr" class=""><<a href="mailto:dnarayan@haverford.edu" target="_blank" class="">dnarayan@haverford.edu</a>></span> wrote:<br class=""></div></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div class=""><div class="h5"><div dir="ltr" class="">Hey YT-dev,<div class=""><br class=""></div><div class="">I've discovered something that I think could maybe be a bug (though maybe not) in the Ramses front end but am unsure about the motivation behind the code so thought I'd check in and try to learn a bit.</div><div class=""><br class=""></div><div class="">In frontends/ramses/data_structures.py, I think the length_unit is set to be the length_unit that comes from the info_xxx.txt file multiplied by the box length. For the example yt data sets, this doesn't impact anything because the box lengths are unity.</div><div class=""><br class=""></div><div class="">In examining some Agora snapshots, however the box lengths are not unity - one that I'm looking at for example has a boxlen of 600. This results in length units that aren't similar to what the info_xxx.txt file says, and more dramatically, mass units that are very different. For example, in one such snapshot, I read from the info file:</div><div class=""><br class=""></div><div class=""><p class="">boxlen = 0.600000000000000E+03<br class="">time = 0.500035810875167E+00<br class="">aexp = 0.100000000000000E+01<br class="">H0 = 0.100000000000000E+01<br class="">omega_m = 0.100000000000000E+01<br class="">omega_l = 0.000000000000000E+00<br class="">omega_k = 0.000000000000000E+00<br class="">omega_b = 0.000000000000000E+00<br class="">unit_l = 0.308656802500000E+22<br class="">unit_d = 0.157339152800000E-25<br class="">unit_t = 0.308687241173998E+17</p><p class="">but if I load this snapshot in yt, I get:</p><p class=""><span class="">>In [2]: </span>print ds.mass_unit<br class="">9.9935115109e+46 g</p><p class=""><span class="">>In [3]: </span>print ds.mass_unit.in_units("Msun")<br class="">5.02586592269e+13 Msun</p><p class="">><span class="">In [4]: </span>print ds.length_unit<br class="">1.851940815e+24 cm</p><p class="">which consequently results in derived quantities from the simulation (like stellar mass) that are totally off (by a factor boxlen**3).</p><p class="">So, I'm writing (as a total Ramses novice) to try to understand the motivation behind multiplying the length unit by the boxlen in the frontend, and if I should be accounting for this factor of boxlen**3 in my analysis, or if this is a bona fide bug.</p><p class="">Thanks, <br class="">-desika</p><p class="">ps I updated this morning:</p><p class="">thundersnow:yt desika$ hg id<br class="">8d3663ac217d+ (yt) tip</p></div></div>
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