From 38fef81c64701b26c013330a1cc0e51c2cf9fe78 Mon Sep 17 00:00:00 2001
From: Oliver Sander <sander@dune-project.org>
Date: Sat, 1 Sep 2012 16:19:42 +0000
Subject: [PATCH] Add some documentation to the dbgs method
Patch by Matthias Wohlmuth
FS 1170
[[Imported from SVN: r1688]]
---
dune/istl/gsetc.hh | 29 +++++++++++++++--------------
1 file changed, 15 insertions(+), 14 deletions(-)
diff --git a/dune/istl/gsetc.hh b/dune/istl/gsetc.hh
index 5dbb0a86..6692c4ab 100644
--- a/dune/istl/gsetc.hh
+++ b/dune/istl/gsetc.hh
@@ -407,16 +407,17 @@ namespace Dune {
rowiterator endi=A.end();
for (rowiterator i=A.begin(); i!=endi; ++i)
{
- rhs = b[i.index()];
+ rhs = b[i.index()]; // rhs = b_i
coliterator endj=(*i).end();
coliterator j=(*i).begin();
- for (; j.index()<i.index(); ++j)
- (*j).mmv(x[j.index()],rhs);
- coliterator diag=j++;
- for (; j != endj; ++j)
- (*j).mmv(x[j.index()],rhs);
- algmeta_itsteps<I-1>::dbgs(*diag,x[i.index()],rhs,w);
+ for (; j.index()<i.index(); ++j) // iterate over a_ij with j < i
+ (*j).mmv(x[j.index()],rhs); // rhs -= sum_{j<i} a_ij * xnew_j
+ coliterator diag=j++; // *diag = a_ii and increment coliterator j from a_ii to a_i+1,i to skip diagonal
+ for (; j != endj; ++j) // iterate over a_ij with j > i
+ (*j).mmv(x[j.index()],rhs); // rhs -= sum_{j>i} a_ij * xold_j
+ algmeta_itsteps<I-1>::dbgs(*diag,x[i.index()],rhs,w); // if I==1: xnew_i = rhs/a_ii
}
+ // next two lines: xnew_i = w / a_ii * (b_i - sum_{j<i} a_ij * xnew_j - sum_{j>=i} a_ij * xold_j) + (1-w)*xold;
x *= w;
x.axpy(K(1)-w,xold);
}
@@ -458,16 +459,16 @@ namespace Dune {
rowiterator endi=A.end();
for (rowiterator i=A.begin(); i!=endi; ++i)
{
- rhs = b[i.index()];
- coliterator endj=(*i).end();
+ rhs = b[i.index()]; // rhs = b_i
+ coliterator endj=(*i).end(); // iterate over a_ij with j < i
coliterator j=(*i).begin();
for (; j.index()<i.index(); ++j)
- (*j).mmv(x[j.index()],rhs);
- coliterator diag=j;
+ (*j).mmv(x[j.index()],rhs); // rhs -= sum_{j<i} a_ij * xnew_j
+ coliterator diag=j; // *diag = a_ii
for (; j!=endj; ++j)
- (*j).mmv(x[j.index()],rhs);
- algmeta_itsteps<I-1>::bsorf(*diag,v,rhs,w);
- x[i.index()].axpy(w,v);
+ (*j).mmv(x[j.index()],rhs); // rhs -= sum_{j<i} a_ij * xnew_j
+ algmeta_itsteps<I-1>::bsorf(*diag,v,rhs,w); // if blocksize I==1: v = rhs/a_ii
+ x[i.index()].axpy(w,v); // x_i = w / a_ii * (b_i - sum_{j<i} a_ij * xnew_j - sum_{j>=i} a_ij * xold_j)
}
}
--
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