===firstname:
Rob
===firstname3:
Joris
===affil6:

===lastname3:
Degroote
===email:
robby.haelterman@mil.be
===keyword_other2:

===lastname6:

===affil5:

===lastname4:
Cracana
===lastname7:

===affil7:

===postal:
Royal Military Academy (MWMW)
Renaissancelaan 30
B-1000 Brussels
Belgium
===ABSTRACT:
Partitioned solution problems have often been solved using the Picard fixed-point iteration because of its simplicity. More recently, Anderson Acceleration has been re-discovered as a sure means to accelerate the Picard iteration. Indeed, it has been proven that, whenever the Picard iteration converges, the Anderson acceleration technique will result in equal or faster convergence. However, as we will show, Anderson acceleration has not always been applied wisely to the Picard iteration, as the fine print of the aforementioned proof is more often than not overlooked.\\
We will show how Anderson can be applied to a convergent Picard iteration, resulting in far worse convergence and even in divergence. We will also explain the reasons for this surprising behavior and present a sure way to avoid it.\\
For this purpose we use a simple fabricated pathological example together with a more elaborate model describing the elementary physics of a plasma inside a Tokamak.
===affil3:
Ghent University
===title:
Does Anderson always Accelerate Picard ?
===affil2:
LPP / Euratom
===lastname2:
Van Eester
===firstname4:
Silviu
===keyword1:
Nonlinear solution methods, nonlinear least squares
===workshop:
no
===lastname:
Haelterman
===firstname5:

===keyword2:
Coupled multi-physics problems: electromagnetics/fluids
===otherauths:

===affil4:
Military Technical Academy
===competition:
no
===firstname7:

===firstname6:

===keyword_other1:

===lastname5:

===affilother:

===firstname2:
Dirk