Gmandel

Gmandel 1.4.2 is now released at the sourceforge download area.
Mar. 25, 2015

What is Gmandel?
Gmandel requirements
Getting latest version of Gmandel
Building Gmandel
Running Gmandel
Gmandel benchmarks
Upcoming releases
Gmandel and the Mandelbrot set
Release notes

What is gmandel?
Gmandel is a C program to generate images of the fractals from the Mandelbrot set and to benchmark the computer or array of computers used. The basic unit of measure is the MMIPS (Million of Mandelbrot Iterations Per Second). Computations are done in quad precision, so a 64 bit procesors speed things up quite a bit.
Gmandel runs on Linux (or equivalent) and may be run on a single computer, a multiprocesor computer (most new multi-core PCs), or a cluster of computers.
In each case, Gmandel can take advantage of multi-core technology by the use of shared memory, fine grained and distributed memory, coarse grain parallel computing techniques. The first is accomplished with posix threads and the latter by means of MPI message passing (currently tested with mpich2, from ANL).

Lastest news
Latest version, 1.4.2, compiled and tested on an ArchLinux cluster using OpenMPI-1.8.4-1, You should also have numactl installed. (pacman -S openmpi numactl)
If you just execute "gmandel" you will create mpi processes and threads on the local host.
To run mpi processes across multiple hosts in the cluster, you should use mpirun, for example,
```
 $ mpirun -np 1 --bind-to core:overload-allowed --machine-file openmpi.hosts gmandel 
 
```
The actual number of processes to use in each image generation is set from the gmandel GUI. The "--bind-to core:overload-allowed" is used to allow specification of more mpi processes than cores available, while "openmpi.hosts" is a file which contains the names of the hosts which make up the cluster.
With 5 ArchLinux boxes (30 cores) I've managed to get over 2500 MMIPS (mega mandel iterations per second).

Gmandel requirements
Gmandel does not require much. It can run on a simple single procesor laptop or on a several hundred node Infiniband/Myrinet computer cluster.
In each case, Gmandel may be configured to use compute resources to the limit.
If run on a cluster, Gmandel requires that the user has permision to remote execute in realtime on the compute nodes. Unfortunately, this is not always the case.
When your computer cluster administrator institutes the policy that the computer cluster is only good for running batch jobs via torque or pbs, you're out of luck. But be thankful that Mordac doesn't insist that you use punch cards to input the source code to your application.
Gmandel requires GTK+2 and all that implies (glibc, pango, atk, cairo, etc.). If these are not installed in the target computer, just go ahead and download them and configure them with the --prefix=$HOME option to create your very own GTK+ system. You can find more about this at the GTK site (library to build graphical user interfaces (GUIs) originally for X Window, small, efficient, flexible) and the GNU operating system.
Gmandel requires posix threads and posix shared memory. This should not be a problem.
Optionally, Gmandel can distribute the computation among a computer cluster by means of Message Passing Interface (MPI), in particular mpich2 from Argonne National Laboratory.
Also note that if you are using MPI support, only the master or login node requires GTK+. The programs that will be spawned on the computation nodes do not require anything special. And if you're not tunneling X over an ssh connection, don't forget to set the DISPLAY environment variable accordingly. Try opening a remote xterm window to see that everything is functioning properly.

Getting latest version of Gmandel
The latest release version (currently 1.3.1) is available at the sourceforge download site: DOWNLOAD.
And the very latest development version is always available via CVS. More information on how to use CVS can be found here.

Building Gmandel
For instalation, do a
```
 # ./configure --prefix=$HOME
 
```
followed by a
```
 make 
 make install
```
This should put the Gmandel executable at $HOME/bin/gmandel and the remote MPI routines at $HOME/bin/gmandel_mpi_slave.
Remember that wherever you install Gmandel should be accesible to all mpi nodes for the mpi version to run.
If you do not specify an install directory via the --prefix= option at the configure script, this will be set to /usr/local. This is probably not what you want. So please set the --prefix= option.
If mpich2 is not installed on the build computer, you can just run Gmandel from the build directory without the make install part.
If mpich2 version is built, then you must copy the executable files in the build directory to the path specified by $prefix/bin. This is why setting the --prefix option to configure is important. Let make install do copying to the correct path for you.
If you don't know how to set the --prefix option, please execute:
```
    # ./configure --help 
```
for further instructions.
You can also do a ./autogen.sh to regenerate the configure script.
Please report any bugs compiling or runnning Gmandel to edscott(at)users.sourceforge.net.

Running Gmandel
Running Gmandel is as easy as writing
```
 # gmandel
 
```
in an xterm, as long as $HOME is in your PATH environment variable (this is usually the case). This is the case with either the threaded version or the MPI-threaded version. If Gmandel was compiled with MPI support (mpich2), and the mpd daemon is not running, Gmandel with fork a subprocess to try and start the mpd daemon and will terminate it when exiting. If mpd is already running, Gmandel will use the running daemon and leave it alone when exiting. The check takes a time, since a subprocess must be spawned and communication established, so if you want to view images faster, make sure mpd is already running and configured for all the hosts you're going to use before Gmandel is invoked.

Gmandel benchmarks
For generation of Mandelbrot fractal images, some benchmarks obtained are as follows

Version Processors Cores Clock (GHz) Architecture Network OS

Threaded 1 1 2.4 ia32 - Gentoo

Threaded 1 2 2.0 ia-32 - Ubuntu

Threaded 1 2 2 AMD-64 - Gentoo

Threaded-MPI 25 25 2 x86-64 Gigabit Gentoo

Upcoming Releases
Currently the configure script checks for GMP (GNU Multi Precision Library). This is not yet used, but will be in an upcoming release. Interesting details appear to come from using Multiprecision, but this may be due to an unresolved bug somewhere...

Gmandel and the Mandelbrot set

Tecnical paper on Gmandel and the Mandelbrot set

Images from previous versions of Gmandel

Release Notes

--- 1.3.1 notes:
PVM version has been dropped.
Julia set generations are not active (only Mandelbrot set).

This version has been tested with:
- posix threads and posix shm
- mpich2

mpich2 details
1. Make sure ssh works without password for all cluster nodes. 
   Individual ssh keys for all nodes should be in the known_hosts file 

2. Hostname of each node should be listed in /etc/hosts at each node.

3. Problem with mpich2:
   If mpd works but mpdboot does not (failing with a "no_port" message),
   this may be due to the fact that "mpd" is in your path but not "mpd.py".
   This occurs when distros (like gentoo) create a directory for all 
   the mpich2 python files. 
   The problem is easily fixed by creating a symlink in the directory 
   where mpd is located (/usr/bin, /usr/local/bin) to wherever mpd.py 
   really is. Example:
# ln -s /usr/bin/mpd /wherever/mpich2/files/are/located/mpd.py

4. Another problem with mpich2:
   Gmandel may fail with a "no msg recvd from mpd 
   (when expecting ack of request).
   This occurs when the default value for a mpi-message timeout 
   is too low for the hardware you are using.
   Either use a faster network for communication
   (infiniband or myrinet, for example) or change the value for 
   recvTimeout from 20 to something larger. This is done in file
   "mpiexec.py" located whereever mpich2 files are (see point 3 above).

5. If mpd is not running when gmandel is invoked, gmandel will 
   try to start mpd and will terminate mpd when exiting. 
   If mpd is already running, gmandel will use the running daemon 
   and leave it alone when exiting. The check for a running mpd
   takes a bit of time, so if you want to view images faster, make
   sure mpd is running and configured for all the hosts you need
   before gmandel is invoked.



For instalation, do a ./configure followed by a make && make install.

Latest CVS version for gmandel is always available at CVS site hosted
as sourceforge.net.

To run the threaded version:
$ "prefix"/bin/gmandel

To run the MPI version (mpich2):
$ mpdboot [optional]
$ "prefix"/bin/gmandel

--------------------------------------------------------------------


Points to remember:
-- You should have the DISPLAY environment variable correctly defined 
   for remote display of the gmandel program. SSH tunnels work fine.
-- You can also do a ./autogen.sh to regenerate the configure script.


Enjoy.

Author

Edscott Wilson García, who can be reached for comments, patches, suggestions at edscott(at)users.sourceforge.net

page last updated: Mar. 25, 2015. Today my dad would have been 83.

Version	Processors	Cores	Clock (GHz)	Architecture	Network	OS
Threaded	1	1	2.4	ia32	-	Gentoo
Threaded	1	2	2.0	ia-32	-	Ubuntu
Threaded	1	2	2	AMD-64	-	Gentoo
Threaded-MPI	25	25	2	x86-64	Gigabit	Gentoo