Hi Troels,
I'm not sure about the kex >= 1e5 check. You have to be careful,
because a number of the analytic models - CR72 possibly included - are
not defined for such timescales (of course this is dependant on the
alpha scale, hence dw has an effect). So there are a series of models
where kex >= 1e5 does not return R20!
Note that if you force the return of R20 when kex >= 1e5 when this is
not valid, then you will introduce a discontinuity into the
chi-squared space
(https://en.wikipedia.org/wiki/Discontinuity_%28mathematics%29).
Discontinuities are 100% fatal for all the local optimisers in minfx
(https://gna.org/projects/minfx/). Therefore it is best to avoid a
check of kex >= 1e5 to force a return of R20.
Cheers,
Edward
On 26 May 2014 13:38, <tlinnet@xxxxxxxxxxxxx> wrote:
Author: tlinnet
Date: Mon May 26 13:38:09 2014
New Revision: 23414
URL: http://svn.gna.org/viewcvs/relax?rev=23414&view=rev
Log:
Critical fix for the math domain catching of model CR72.
This was discovered with the added 8 unit tests demonstrating edge case 'no
Rex' failures.
This follows from the ideas in the post
http://article.gmane.org/gmane.science.nmr.relax.devel/5858.
This is related to: task #7793: (https://gna.org/task/?7793) Speed-up of
dispersion models.
This is to implement catching of math domain errors, before they occur.
When kex is large, ex: kex = 1e5, the values of:
etapos = eta_scale * sqrt(Psi + sqrt_psi2_zeta2) / cpmg_frqs
will exceed possible numerical representation.
The cathing of these occurences needed to be re-written.
Modified:
branches/disp_speed/lib/dispersion/cr72.py
Modified: branches/disp_speed/lib/dispersion/cr72.py
URL:
http://svn.gna.org/viewcvs/relax/branches/disp_speed/lib/dispersion/cr72.py?rev=23414&r1=23413&r2=23414&view=diff
==============================================================================
--- branches/disp_speed/lib/dispersion/cr72.py (original)
+++ branches/disp_speed/lib/dispersion/cr72.py Mon May 26 13:38:09 2014
@@ -128,9 +128,9 @@
k_BA = pA * kex
k_AB = pB * kex
- # Catch parameter values that will result in no exchange, returning
flat R2eff = R20 lines.
- if dw == 0.0 or pA == 1.0 or kex == 0.0:
- return array([r20_kex]*num_points)
+ # Catch parameter values that will result in no exchange, returning
flat R2eff = R20 lines (when kex = 0.0, k_AB = 0.0).
+ if dw == 0.0 or pA == 1.0 or k_AB == 0.0 or kex >= 1.e5:
+ return array([r20a]*num_points)
# The Psi and zeta values.
if r20a != r20b:
@@ -156,16 +156,12 @@
# Catch math domain error of cosh(val > 710).
# This is when etapos > 710.
if max(etapos) > 700:
- R2eff = array([1e100]*num_points)
-
- return R2eff
+ return array([r20a]*num_points)
# The arccosh argument - catch invalid values.
fact = Dpos * cosh(etapos) - Dneg * cos(etaneg)
if min(fact) < 1.0:
- R2eff = array([r20_kex]*num_points)
-
- return R2eff
+ return array([r20_kex]*num_points)
# Calculate R2eff.
R2eff = r20_kex - cpmg_frqs * arccosh( fact )
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Re: r23414 - /branches/disp_speed/lib/dispersion/cr72.py