r18587 - /trunk/generic_fns/structure/main.py -- March 01, 2013 - 17:41

Author: bugman
Date: Fri Mar  1 17:41:31 2013
New Revision: 18587

URL: http://svn.gna.org/viewcvs/relax?rev=18587&view=rev
Log:
The structure.find_pivot user function now uses the logarithmic barrier 
function.

This is for constrained optimisation and requires the newest minfx code.  The 
pivot position is
constrained within a box of +/- 1000 Angstroms from zero.  This is needed for 
when the solution is
an infinite line - i.e. a rotation axis and not a pivot point.  Previously 
the simplex optimisation
would head toward + or - infinity.  But now with a logarithmic barrier, the 
simplex algorithm can
stabilise and find a point on the axis very quickly, long before reaching the 
edges of the box.


Modified:
    trunk/generic_fns/structure/main.py

Modified: trunk/generic_fns/structure/main.py
URL: 
http://svn.gna.org/viewcvs/relax/trunk/generic_fns/structure/main.py?rev=18587&r1=18586&r2=18587&view=diff
==============================================================================
--- trunk/generic_fns/structure/main.py (original)
+++ trunk/generic_fns/structure/main.py Fri Mar  1 17:41:31 2013
@@ -246,9 +246,18 @@
         coord[-1] = array(coord[-1])
     coord = array(coord)
 
+    # Linear constraints for the pivot position (between -1000 and 1000 
Angstrom).
+    A = zeros((6, 3), float64)
+    b = zeros(6, float64)
+    for i in range(3):
+        A[2*i, i] = 1
+        A[2*i+1, i] = -1
+        b[2*i] = -1000
+        b[2*i+1] = -1000
+
     # The target function.
     finder = Pivot_finder(models, coord)
-    results = generic_minimise(func=finder.func, x0=init_pos, 
min_algor='simplex', func_tol=func_tol, print_flag=2)
+    results = generic_minimise(func=finder.func, x0=init_pos, min_algor='Log 
barrier', min_options=('simplex',), A=A, b=b, func_tol=func_tol, print_flag=1)
 
     # No result.
     if results == None: