<div dir="ltr"><div class="gmail_extra"><br><div class="gmail_quote">On Fri, Nov 22, 2013 at 1:01 PM, dave fournier <span dir="ltr"><<a href="mailto:davef@otter-rsch.com" target="_blank">davef@otter-rsch.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<div bgcolor="#FFFFFF" text="#000000">
<div>On 13-11-21 06:29 PM, Alex Campbell
wrote:<br>
<br>
I'm not sure I understand this.<br>
<br>
what does this mean?<div class="im"><br>
<br>
mceval output inconsistent with mcmc display"<br>
<br>
<br></div></div></div></blockquote><div><br>It is the subject line of the email to this list in which I first reported this issue. <br><br> <br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<div bgcolor="#FFFFFF" text="#000000"><div><div class="im"></div>
I know I wrote the mcmc stuff really fast and wanted some output
that I could plot with gnuplot<br>
for a useless meeting in 1992.<br>
It worked fine with a good model, but not with a "bad" model. The
mceval stuff was really meant<br>
to supercede it i.e if you got good results with the display fine,
but the real output was intended to<br>
be the mceval stuff.<br>
<br></div></div></blockquote><div><br></div><div>Actually the mceval stuff will be wrong too if you have an unidentifiable model on windows/mingw, complete with a bogus std file. On a real system, ie linux-gcc, once the estimation phase is complete, it will give a diagnostic message and quit. No std file will be produced. <br>
</div><div> </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div bgcolor="#FFFFFF" text="#000000"><div>
I wonder what happens with R if you write a model with
unidentifiable parameters?<br>
<br></div></div></blockquote><div><br>Good question.<br> <br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div bgcolor="#FFFFFF" text="#000000">
<div>
There is a standard thing I use (or used to use back when I was
still alive) I would put a small quadratic penalty<br>
on all the parameters when the problem seemed degenerate. with a
little bit of tuning it was usually<br>
possible to find where the unidentifiability was.<br>
<br>
Anyway if you are trying to convince a someone of the value of
ADMB, I can think of better ways than<br>
trying to fit a model with unidentifiable parameters.<br>
<br>
<br></div></div></blockquote><div><br>In theory you never build models with unidentifiable parameters. In practice, at least in my experience, it comes up regularly, especially if you're playing with spatial stuff. This is a problem if you can't rely on your tools to tell you you're being a blockhead. You say "when the problem seemed degenerate".. the issue is how do you know this from ADMB output? If you have a degenerate model-data combination, on a windows system with mingw all bets are off. If you aren't experienced enough to guess that degeneracy / unidentifiability may be the issue ADMB won't tell you. There are other, subtler discrepancies between ADMB on windows and linux. At work I'm forced to use windows but for stock assessments I will always cross check with a linux box. I know you guys are putting a lot of work into making things easy for new windows users, which is great.. I think ADMB is an amazing piece of kit. It is just unfortunate it is being (or at least has been in the past) let down by a substandard operating system and/or compiler.<br>
</div><div></div><div><br></div><div>You could include this in the testing. Just add a misspecified model-data combination to the examples. <br></div><div> </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<div bgcolor="#FFFFFF" text="#000000"><div>
<br>
</div><div><div class="h5">
<blockquote type="cite">
<div dir="ltr">I posted on this a couple of years ago. See "mceval
output inconsistent with mcmc display". The last word there is
me saying I've figured it out and I'll send you the code to
reproduce the issue off list. Can't remember if I did, and don't
have access to those emails to check. I think I did send it to
you and never heard back. I assumed since no one else had come
across this since that time it might have been resolved with
updates to the mingw compiler. But no. Came across it again
about six months ago on another model, ADMB version 10 i think
or maybe 10.1. I was in the process of winning over a colleague
to the ADMB cause and had to basically say well its great but
its broken on windows. We ran the same code, same inputs on
linux and it diagnosed the unidentifiability (can't remember the
exact message but i assume it was telling us that the hessian
was singular to machine precision). We had an unidentifiable
virgin recruitment in one spatial region, which made sense in
hindsight. If you can't find the code and inputs I sent you in
June-July 2011 (or if I didn't?) I can dig around for the more
recent model. Can't remember if I've checked this out on a
visual studio compiler but I have a hunch the issue is mingw not
windows in general.<br>
</div>
<div class="gmail_extra"><br>
<br>
<div class="gmail_quote">On Fri, Nov 22, 2013 at 1:19 AM, dave
fournier <span dir="ltr"><<a href="mailto:davef@otter-rsch.com" target="_blank">davef@otter-rsch.com</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<div>My experience of the mingw compiler is that
with it ADMB fails to diagnose singular or near singular
hessians. This is a minefield for inexperienced users and
in my opinion it should not be supported. Has no one else
seen this issue?<br>
Alex<br>
<br>
</div>
That seems highly unlikely in the sense that the mingw
compiler would be different<br>
from any other compiler in this manner. Do you have an
example?
<div>
<div><br>
_______________________________________________<br>
Users mailing list<br>
<a href="mailto:Users@admb-project.org" target="_blank">Users@admb-project.org</a><br>
<a href="http://lists.admb-project.org/mailman/listinfo/users" target="_blank">http://lists.admb-project.org/mailman/listinfo/users</a><br>
</div>
</div>
</blockquote>
</div>
<br>
</div>
</blockquote>
<br>
</div></div></div>
</blockquote></div><br></div></div>