Re: [Yt-dev] yt-hop configuration improvements?

23 Mar 2009

      In hop.c these are the defaults:

    nBucket = 16;
    nDens = 64;
    nHop = -1;
    fDensThresh = -1.0;
    bSym = 1;
    bTopHat = 0;
    nMerge = 4;

bSym and bTopHat are 0/1, nBucket,nSmooth,nDens,nHop, and nMerge are ints, fDensThresh is a float. if fDensThresh is to be >0, it needs to be multipled by the same ratio that the threshold is in SS_HopOutput for it to be correct.

nBucket - Performance tuning in kd-tree search.
nDens - N_dens -- # of particles to smooth for density, default 64.
nHop - N_hop -- # of particles over which to look for density max, default 16.
fDensThresh - Density below which we don't assign to any group, default none.
bSym - Use gather-only for spline kernal, else gather-scatter.
bTopHat - Use tophat kernal for density, else cubic spline.
nMerge - N_merge -- # of particles to catalog group boundaries, default 4.

in regroup.c:

    c->peak_thresh   = 3.0*dens_outer;
    c->saddle_thresh = 2.5*dens_outer;
    c->densthresh    = dens_outer;
    c->mingroupsize = -1;

The defaults are fine here, which puts c->peak_thresh and c->saddle_thresh at a fixed ratio of c->densthresh, but sometimes we want to make them different. Also, the mingroupsize makes a large difference and needs to be adjustible.

c->mingroupsize -- Minimum group size.
c->peak_thresh - Density required at group center
c->saddle_thresh - Density required at boundary
c->densthresh - Density required for a particle to be in a group

Let me know if you want help, Matt!

 _______________________________________________________
sskory@physics.ucsd.edu           o__  Stephen Skory
http://physics.ucsd.edu/~sskory/ _.>/ _Graduate Student
________________________________(_)_\(_)_______________

----- Original Message ----
...
From: Matthew Turk 
To: yt-dev@lists.spacepope.org
Sent: Sunday, March 22, 2009 10:30:24 PM
Subject: Re: [Yt-dev] yt-hop configuration improvements?
Stephen, why don't you post the list of parameters here, and I'll add
them all as keywords inside the C function?  I don't mind doing it.
:)
-Matt
On Sun, Mar 22, 2009 at 10:04 PM, Stephen Skory wrote:
...
...
I'll try to add these options tomorrow.
I'll post the changes to codereview before committing...
_______________________________________________________
sskory@physics.ucsd.edu           o__  Stephen Skory
http://physics.ucsd.edu/~sskory/ _.>/ _Graduate Student
________________________________(_)_\(_)_______________
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