[pypy-commit] extradoc extradoc: explain why we are doing better on the large parameter variants

[cfbolz]

Author: Carl Friedrich Bolz <cfbolz at gmx.de>
Branch: extradoc
Changeset: r4652:3f24096e585b
Date: 2012-08-17 10:54 +0200
http://bitbucket.org/pypy/extradoc/changeset/3f24096e585b/

Log:	explain why we are doing better on the large parameter variants

diff --git a/talk/dls2012/paper.tex b/talk/dls2012/paper.tex
--- a/talk/dls2012/paper.tex
+++ b/talk/dls2012/paper.tex
@@ -1102,11 +1102,17 @@
 short and a significant amount of time is spent in the outer loops. This is the case 
 with for example SparseMatMult.
 
+The large input parameters of the SciMark benchmarks are chosen in such a way
+to make the problem not fit into the CPU cache. This explains why PyPy is doing
+relatively better on them. The cache miss penalties are large relative to the
+time needed to perform the actual computations, which hides problems of the
+less efficient code generated by PyPy.
+
 The speedups that LuaJIT gains from the loop optimization pass are similar to
 those PyPy gains. In general, LuaJIT is even closer to C performance, sometimes
 even surpassing it. LuaJIT is generating machine code of higher quality because
 it has more optimizations\footnote{See
-\texttt{http://wiki.luajit.org/Optimizations}} and is a produces much better
+\texttt{http://wiki.luajit.org/Optimizations}} and produces much better
 machine code than PyPy.
 
 \section{Related Work}