[cig-commits] [commit] master: Reduce the aggregation threshold for the AMG. (fdc9f02)

[cig_noreply at geodynamics.org]

Repository : https://github.com/geodynamics/aspect

On branch  : master
Link       : https://github.com/geodynamics/aspect/compare/36e4420c87fda8026b8a3d1f639e798f6c59f3d0...01f19ef36177d8c77f84b59ece4918ba5f3e7661

>---------------------------------------------------------------

commit fdc9f026287c1e0791c3f154acc55e075aaa03a6
Author: Wolfgang Bangerth <bangerth at math.tamu.edu>
Date:   Fri Dec 5 17:24:26 2014 -0600

    Reduce the aggregation threshold for the AMG.
    
    On the Davies et al. benchmark (case 1.1) this reduces the time for the
    Stokes solver from 436 to 352 seconds. On the case discussed previously
    in this pull request, it reduces the solver time almost by a factor of 2.


>---------------------------------------------------------------

fdc9f026287c1e0791c3f154acc55e075aaa03a6
 doc/modules/changes.h        | 6 ++++++
 source/simulator/assembly.cc | 4 ++--
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/doc/modules/changes.h b/doc/modules/changes.h
index 65eb14f..01b1eb8 100644
--- a/doc/modules/changes.h
+++ b/doc/modules/changes.h
@@ -10,6 +10,12 @@
  * <br>
  * (Timo Heister, 2015/01/13)
  *
+ * <li> New: The parameters for the inner Algebraic Multigrid preconditioner
+ * used in the Stokes solve have been tuned to achieve a speedup of the solver
+ * phase by a factor between 1.2 and 2, depending on application.
+ * <br>
+ * (Wolfgang Bangerth, 2014/12/05)
+ *
  * <li> New:  There is now the option to specify an origin when using the box
  * goemetry model.
  * <br>
diff --git a/source/simulator/assembly.cc b/source/simulator/assembly.cc
index 7a5b912..06be596 100644
--- a/source/simulator/assembly.cc
+++ b/source/simulator/assembly.cc
@@ -1,5 +1,5 @@
 /*
-  Copyright (C) 2011 - 2014 by the authors of the ASPECT code.
+  Copyright (C) 2011 - 2015 by the authors of the ASPECT code.
 
   This file is part of ASPECT.
 
@@ -1028,7 +1028,7 @@ namespace aspect
     Amg_data.elliptic = true;
     Amg_data.higher_order_elements = true;
     Amg_data.smoother_sweeps = 2;
-    Amg_data.aggregation_threshold = 0.02;
+    Amg_data.aggregation_threshold = 0.001;
 #endif
 
     /*  The stabilization term for the free surface (Kaus et. al., 2010)