document how performance scales with number of processors

git-svn-id: http://svn.einsteintoolkit.org/cactus/EinsteinAnalysis/AHFinderDirect/trunk@923 f88db872-0e4f-0410-b76b-b9085cfa78c5

1 files changed, 14 insertions, 12 deletions

diff --git a/doc/documentation.tex b/doc/documentation.tex
index e03538e..ba0439c 100644
--- a/doc/documentation.tex
+++ b/doc/documentation.tex
@@ -272,18 +272,20 @@ here's what works and what doesn't:
 	these thorns compiled into your configuration and activated.
 \item	\thorn{AHFinderDirect} works in multi-processor Cactus runs,
 	but at present it's quite inefficient for large numbers of
-	processors.  (It exhibits ``anti-scaling'' with the number
-	of processors: the run time gets {\em larger\/} as the number
-	of processors increases.)%%%
-\footnote{%%%
-	 The run time on $N$ processors should be roughly
-	 $\alpha + \beta N$ for some (positive!) constants
-	 $\alpha$ and $\beta$.  I estimate the value of $N$
-	 for which the run time is twice the single-processor
-	 value, to be on the order of 10 to 20 for the current
-	 implementation.%%%
-	 }%%%
-{}	I hope to fix this inefficiency soon.
+	processors.  In fact, it exhibits ``anti-scaling'' with the
+	number of processors: the run time is {\em larger\/} as the
+	number of processors increases.  I hope to fix this inefficiency
+	soon, but for now, the run time relative to the single-processor
+	case is roughly
+	\begin{flushleft}
+	\begin{tabular}{cc}
+	$N$		& $t_N / t_1$		\\
+	\hline
+	2		& 1.4			\\
+	4		& 2.0			\\
+	$N>4$		& $1.55 + 0.12N$	%%%\\
+	\end{tabular}
+	\end{flushleft}
 \end{itemize}
 
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