## Feb 27, 2010

### Plot data file with PGFPlot

Tikz and pgfplot can plot data file in Tex.

\begin{figure}
\begin{center}
\begin{tikzpicture}[scale=0.3]
\begin{axis}[xlabel=nstep, ylabel=WaveHeight]
\addplot[mark=none] file {case14.data};   % Here is the data file
\legend{True, Predicted};
\end{axis}
\end{tikzpicture}
\begin{tikzpicture}[scale=0.3]
\begin{axis}[xlabel=nstep, ylabel=error(2-norm)]
\end{axis}
\end{tikzpicture}
\end{center}
\caption{(a)True and predicted wave height at the domain center; (b)2-norm of numerical error on the whole domain}
\end{figure}

The data file's format can be multiple columns separated by space. Each column is for one variable. Such as
# data file
0.00001 2.123243
0.00003 3.123452
......
Sometimes, Matlab's fprintf function may help to generate such data file.
For example:
fid = fopen('case14err.data','w');
b=1/650:6.5/650:6.5;
y=[b ; a];
fprintf(fid,'%1.5f %1.5f\n', y);
fclose(fid);

## Feb 26, 2010

### A script to create shared lib

A good script to create shared lib

1. With root privileges: create directories /usr/local/lib and /usr/local/include (if not exist)
2. add pass for /usr/local/lib in file /etc/ld.so.conf (if not exists)
3. run script: create_shared_lib.sh (text below)
f.e. you have money.c file that is prepared for creating library "money".
$sh create_shared_lib money 4. copy your money.h to /usr/local/include 5. to use your library: include money.h in global area of your program (#include &ltmoney.h>) gcc -Wall -g -o my_prog.exe my_prog.c -I/usr/local/include -lmoney 1. Without root privileges: create directory lib and include in your$HOME directory
2. change script's line 'mv "$libname".* /usr/local/lib/' for 'mv "$libname".* ~/lib/'
3. comment line 'ldconfig &'
4. run script (as I explained above)
include money.h in global area of your program (#include &ltmoney.h>)
gcc -Wall -g -o my_prog.exe my_prog.c -I$HOME/include -L$HOME/lib -lmoney

create_shared_lib.sh

#!/bin/bash

ARG=1
if [ "$#" -ne "$ARG" ]
then
echo -e "\t\tUsages: basename $0 name_of_shared_library" exit$BADARG
fi

libname=lib"$1" ########################################################################## # uncomment next 2 lines and comment 3-4 lines if you create C++ library # ########################################################################## #g++ -fPIC -c "$1".cpp
#g++ -shared -Wl,-soname,"$libname".so.1 -o "$libname".so.1.0 "$1".o gcc -fPIC -c "$1".c
gcc -shared -Wl,-soname,"$libname".so.1 -o "$libname".so.1.0 "$1".o ln -s "$libname".so.1.0 "$libname".so.1 ln -s "$libname".so.1 "$libname".so echo -e "\t\tSHARED LIBRARY$libname IS CREATED"
echo -e "\t\t==================================\n"
echo
mv "$libname".* /usr/local/lib/ echo -e "\t\tldconfig is working" ldconfig & exit 0 ## Feb 13, 2010 ### Node plot and position in Tikz It is difficult to create a neat, accurate and fancy scientific figure. Tikz/pgf, pstricks, metapost are not easy to learn, nor for me to have a full knowledge of their capabilities. On the other hand, gimp or photoshop is not suitable to produce figures from calculated data. I hope there will be a very handy tool that can help me using Tikz, or metapost easily. But I tested several java based front end. None of them would be a choice. Here is an example of plotting nodes and point them to each other with arrows, with position determination. It is mainly about '\node', '\draw' and their decoration. It is easy to understand how it is produced, hence, I put no comments here. ----------------------- \begin{tikzpicture} \draw[dash pattern=on 2pt off 3pt on 4pt off 4pt](2,.2) -- (2,3.2); \draw[dash pattern=on 2pt off 3pt on 4pt off 4pt](4,.2) -- (4,3.2); \draw[dash pattern=on 2pt off 3pt on 4pt off 4pt](6,.2) -- (6,3.2); \node at (2,2.9) [fill=blue!50,draw,circle, drop shadow, label=left:\tiny{$x_k^b$}] (n1){}; \node at (2,1.9) [fill=red!50,draw,circle, drop shadow,label=left:\tiny{$x_k^a$}] (n2){}; \node at (2,.9) [fill=green!50,draw,circle, drop shadow,label=left:\tiny{$y_k^o$}] (n3){}; \node at (4,1.9) [fill=red!50,draw,circle, drop shadow,label=left:\tiny{$x_{k+1}^a$}] (n4){}; \node at (4,2.9) [fill=blue!50,draw,circle, drop shadow,label=left:\tiny{$x_{k+1}^b$}] (n5){}; \node at (4,.9) [fill=green!50,draw,circle, drop shadow,label=left:\tiny{$y_{k+1}^o$}] (n6){}; \node at (6,1.9) [fill=red!50,draw,circle, drop shadow,label=left:\tiny{$x_{k+2}^a$}] (n7){}; \node at (6,.9) [fill=green!50,draw,circle, drop shadow,label=left:\tiny{$y_{k+2}^o$}] (n8){}; \node at (6,2.9) [fill=blue!50,draw,circle, drop shadow,label=left:\tiny{$x_{k+2}^b$}] (n9){}; \node at (8,2.9) [fill=blue!20, anchor=base](n10){$\cdots$}; \draw[->, line width=1pt] (1,0.2) -- (10,0.2) node[right]{time}; \node at (2,0.2)[below]{\tiny{$k$}}; \node at (4,0.2)[below]{\tiny{$k+1$}}; \node at (6,0.2)[below]{\tiny{$k+2$}}; \end{tikzpicture} \begin{tikzpicture}[overlay] \path[->] (n2) edge [bend right] (n5); \path[->] (n4) edge [bend right] (n9); \path[->] (n7) edge [bend right] (n10); \end{tikzpicture} \vspace{7mm} \begin{itemize} \item \tikz\node [fill=blue!50,draw,circle]{}; Background state$x^b$\item \tikz\node [fill=red!50,draw,circle]{}; Analysis state$x^a$\item \tikz\node [fill=green!50,draw,circle]{}; Observation$y^o$\end{itemize} ## Feb 12, 2010 ### Install TeXLive on Ubuntu To install texlive2008 1. sudo mount -o loop textlive2008-20080822.iso /mnt 2. cd /mnt 3. ./install-tl -gui If there is error about "Cannot load Tk, maybe something is missing" or "perl/Tk unusable, cannot create main windows.", Follow its suggestion, visit http://tug.org/texlive/distro.html#perltk 4. sudo apt-get install perl-tk 5. sudo ./install-tl -gui Make wise choice, default dir /usr/local/texlive/, click Install TeX Live Download TexMaker, Install it. In configure, add correct path for each executable file, such as /usr/local/texlive/2008/bin/i386-linux/latex. In this way, those programs can be found. 6. sudo vi ~/.bashrc and/or sudo vi /root/.bashrc Add one line at last export PATH=$PATH:/usr/local/texlive/2008/bin/i386-linux

To launch the tlmgr,
7. sudo su
8. tlmgr -gui
If the path is not set in the bashrc, there is error when you launch the tlmgr, even if you execute it from its directory. The error are like:
Can't exec "kpsewhich"
Can't locate TeXLive/TLPOBJ.pm in @INC
So just ass the path of TexLive installation directory.

It is better to install texlive to somewhere does not require root. i.e. /home/yourname/textlive . But the 7th step solves this problem.

## Feb 7, 2010

### mpdtrace and using multiple nodes to run mpi

In a cluster, which the user may need to launch the mpd manually, here are descriptions of to-dos. The situation that one may consider to do so, is when you launch a executable program on multiple nodes, however, there is only the local node is used. Or you see some error like MPI connection or communication error. It is the time to check if all the nodes listed in the hosts file are able to communicate with each other. Error like: mpiexec: unable to start all procs; may have invalid machine names remaining specified hosts.

Following description works for MPICH2, using mpiexec ot mpirun. That is how I tested.

On the node where you launch the program, type
>> mpdtrace -l
It gives you  <node name>_<port>(IP)

If not all nodes are listed here, for example, if blade46 is in the hosts file, and is available. ssh to blade46, type
>>mpd -h blade50 -p 51094 &
If you want to start more mpd
>>mpd -h blade50 -p 51094 -n &
Then the blade46 can be used.

To clean up mpd daemon, use mpdcleanup

Besides, if you want to launch m consecutive ranks on the same node, use mpd --ncpus=m
For example:
mpd --ncpus=2 &
or
mpd --ncpus=2 -h blade50 -p 51094 &

QUOTE"
If an mpd is started with the --ncpus option, then when it is its turn to start a process, it will start several application processes rather than just one before handing off the task of starting more processes to the next mpd in the ring. For example, if the mpd is started with
mpd --ncpus=4

then it will start as many as four application processes, with consecutive ranks, when it is its turn to start processes. This option is for use in clusters of SMP's, when the user would like consecutive ranks to appear on the same machine. (In the default case, the same number of processes might well run on the machine, but their ranks would be different.) (A feature of the --ncpus=[n] argument is that it has the above effect only until all of the mpd's have started n processes at a time once; afterwards each mpd starts one process at a time. This is in order to balance the number of processes per machine to the extent possible.)
"END of QUOTE

## Feb 5, 2010

### Animate image files

With a sequence of image files, we can code them into a video file. Suppose that they are named beginning from 1, use

ffmpeg -qscale 1 -r 20 -b 96000 -i %08d.png animate.mp4

If the file names do not start from 1, we can use a script do rename them in batch.

#!/bin/bash

d=1
for fname in *.png
do
mv $fname printf "%08d.png"$d
d=$(($d+1))
done

To enable mp3 etc.
>>sudo apt-get install ffmpeg libavcodec-extra-52
One example of extracting audio from mp4:
>>ffmpeg -ss 00:05:00:00 -t 00:02:00:00 -i input.mp4 -acodec libmp3lame -ab 128k output.mp3
ss: time offset from beginning of input in hh:mm:ss:frames.
t: duration of encode
ab: audio bitrate