/[escript]/trunk/escript/py_src/pdetools.py
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revision 790 by bcumming, Wed Jul 26 23:12:34 2006 UTC revision 867 by gross, Mon Oct 9 06:50:09 2006 UTC
# Line 7  Currently includes: Line 7  Currently includes:
7      - Projector - to project a discontinuous      - Projector - to project a discontinuous
8      - Locator - to trace values in data objects at a certain location      - Locator - to trace values in data objects at a certain location
9      - TimeIntegrationManager - to handel extraplotion in time      - TimeIntegrationManager - to handel extraplotion in time
10        - SaddlePointProblem - solver for Saddle point problems using the inexact uszawa scheme
11    
12  @var __author__: name of author  @var __author__: name of author
13  @var __copyright__: copyrights  @var __copyright__: copyrights
# Line 353  class Locator: Line 354  class Locator:
354          else:          else:
355             return data             return data
356    
357    class SaddlePointProblem(object):
358       """
359       This implements a solver for a saddlepoint problem
360    
361       f(u,p)=0
362       g(u)=0
363    
364       for u and p. The problem is solved with an inexact Uszawa scheme for p:
365    
366       Q_f (u^{k+1}-u^{k}) = - f(u^{k},p^{k})
367       Q_g (p^{k+1}-p^{k}) =   g(u^{k+1})
368    
369       where Q_f is an approximation of the Jacobiean A_f of f with respect to u  and Q_f is an approximation of
370       A_g A_f^{-1} A_g with A_g is the jacobiean of g with respect to p. As a the construction of a 'proper'
371       Q_g can be difficult, non-linear conjugate gradient method is applied to solve for p, so Q_g plays
372       in fact the role of a preconditioner.
373       """
374       def __init__(self,verbose=False,*args):
375           """
376           initializes the problem
377    
378           @parm verbose: switches on the printing out some information
379           @type verbose: C{bool}
380           @note: this method may be overwritten by a particular saddle point problem
381           """
382           self.__verbose=verbose
383    
384       def trace(self,text):
385           """
386           prints text if verbose has been set
387    
388           @parm text: a text message
389           @type text: C{str}
390           """
391           if self.__verbose: print "%s: %s"%(str(self),text)
392    
393       def solve_f(self,u,p,tol=1.e-7,*args):
394           """
395           solves
396    
397           A_f du = f(u,p)
398    
399           with tolerance C{tol} and return du. A_f is Jacobiean of f with respect to u.
400    
401           @param u: current approximation of u
402           @type u: L{escript.Data}
403           @param p: current approximation of p
404           @type p: L{escript.Data}
405           @param tol: tolerance for du
406           @type tol: C{float}
407           @return: increment du
408           @rtype: L{escript.Data}
409           @note: this method has to be overwritten by a particular saddle point problem
410           """
411           pass
412    
413       def solve_g(self,u,*args):
414           """
415           solves
416    
417           Q_g dp = g(u)
418    
419           with Q_g is a preconditioner for A_g A_f^{-1} A_g with  A_g is the jacobiean of g with respect to p.
420    
421           @param u: current approximation of u
422           @type u: L{escript.Data}
423           @return: increment dp
424           @rtype: L{escript.Data}
425           @note: this method has to be overwritten by a particular saddle point problem
426           """
427           pass
428    
429       def inner(self,p0,p1):
430           """
431           inner product of p0 and p1 approximating p. Typically this returns integrate(p0*p1)
432           @return: inner product of p0 and p1
433           @rtype: C{float}
434           """
435           pass
436    
437       def solve(self,u0,p0,tolerance=1.e-6,*args):
438           pass
439  # vim: expandtab shiftwidth=4:  # vim: expandtab shiftwidth=4:

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