Commit 525314f3 authored by Dominic Etienne Charrier's avatar Dominic Etienne Charrier
Browse files

Add information. How to refine the mesh further.

parent 9691c549
...@@ -392,19 +392,19 @@ metric if you switch this feature on (\texttt{hotspot}, e.g.). ...@@ -392,19 +392,19 @@ metric if you switch this feature on (\texttt{hotspot}, e.g.).
\subsection{Meshes for weak and strong scaling} \subsection{Meshes for weak and strong scaling}
ExaHyPE distributes work by decomposing the tripartitioned spacetree into \exahype distributes work by decomposing the tripartitioned spacetree into
subtrees that are deployed to worker processes. subtrees that are deployed to worker processes.
Only subtrees that overlap with the computational domain are deployed. Only subtrees that overlap with the computational domain are deployed.
This constraint can be used to steer work distribution. This constraint can be used to steer work distribution.
ExaHyPE can scale the bounding box such that \texttt{outside\_cells\_left} and/or \texttt{outside\_cells\_right} cells are placed outside of the \exahype can scale the bounding box such that \texttt{outside\_cells\_left} and/or \texttt{outside\_cells\_right} cells are placed outside of the
domain while the latter is still resolved as accurately as specified in the spec file. domain while the latter is still resolved as accurately as specified in the spec file.
Furthermore, there is an option to place exactly \texttt{ranks\_per\_dimension" on the coarse grid}. Furthermore, there is an option to place exactly \texttt{ranks\_per\_dimension" on the coarse grid}.
(Note: This overrules \texttt{outside\_cells\_right} but not \texttt{outside\_cells\_left}. (Note: This overrules \texttt{outside\_cells\_right} but not \texttt{outside\_cells\_left}.
This feature is particular interesting for weak scaling experiments as it can scale the number of cells per dimension This feature is particular interesting for weak scaling experiments as it can scale the number of cells per dimension
of a mesh by arbitrary integers. of a mesh by arbitrary integers.
An example is given below: An example is given in Fig. \ref{fig:weak-scaling}:
\begin{figure}[h] \begin{figure}[h]
\begin{center} \begin{center}
...@@ -416,23 +416,25 @@ An example is given below: ...@@ -416,23 +416,25 @@ An example is given below:
\includegraphics[width=0.4\textwidth]{sketches/weak-scaling-8.pdf} \includegraphics[width=0.4\textwidth]{sketches/weak-scaling-8.pdf}
\end{center} \end{center}
\caption{Weak scaling experiment growing the domain by factors $1$, $2^d$, $4^d$, and $8^d$. \texttt{ranks\_per\_dimension} is chosen 1,2,4,8.} \caption{Weak scaling experiment growing the domain by factors $1$, $2^d$, $4^d$, and $8^d$. \texttt{ranks\_per\_dimension} is chosen 1,2,4,8.}
} \label{fig:weak-scaling}
\end{figure} \end{figure}
The bounding box scaling controls can be used to create interesting meshes as The bounding box scaling controls can be used to create interesting meshes as
the $36^d$ cell mesh given below. This mesh was created with 9 outside cells the $36^d$ cell mesh shown in Fig. \ref{fig:strong-scaling}. This mesh was created with 9 outside cells
on the left side and 12 ranks per dimension. The mesh on the left side and 12 ranks per dimension. The mesh
is interesting since it can be perfectly distributed among is interesting since it can be perfectly distributed among
$2^d$, $4^d$, and $12^d$ processes. $2^d$, $4^d$, and $12^d$ processes.
The same mesh refined by a factor $3^i$, $i \leq 1$ can be constructed if $3^i \times 9$ bounding box outside cells
are placed to the left of the domain.
\begin{figure}[h] \begin{figure}[h]
\begin{center} \begin{center}
\includegraphics[width=0.5\textwidth]{sketches/strong-scaling-grid-223.pdf} \includegraphics[width=0.5\textwidth]{sketches/strong-scaling-grid-223.pdf}
\end{center} \end{center}
\caption{% \caption{A grid with $36^d$ cells on the coarse grid which allows to use $1$, $2^d$, $4^d$, and $12^d$ ranks
A grid with $36^d$ cells on the coarse grid which allows to use $1$, $2^d$, $4^d$, and $12^d$ ranks to uniformly distribute the load.}
to uniformly distribute the load. \label{fig:strong-scaling}
}
\end{figure} \end{figure}
\section{MPI troubleshooting and inefficiency patterns} \section{MPI troubleshooting and inefficiency patterns}
......
Markdown is supported
0% or .
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment