Multicore - Parallel processing on multiple cores

This package provides parallel processing on multiple cores/machines.

Description

This package provides parallel processing on multiple cores on a single machine or on multiple machines that have access to a common directory.

If you have multiple function calls that are independent of each other, and you can reformulate your code as

for k = 1:numel(parameterCell)
  resultCell{k} = myfun(parameterCell{k});
end

then, replacing the loop by

resultCell = startmulticoremaster(@myfun, parameterCell);

allows you to evaluate your loop in parallel. All you need to do is to start as many additional Matlab sessions/processes as you want slaves to work, and to run

startmulticoreslave

in those additional Matlab sessions.

Everything is programmed in plain and platform-independent Matlab - no toolboxes are used, no compilation of mex-files is necessary.

Please get started with 1. the documentation in file multicore.html, 2. the help lines of function startmulticoremaster.m and 3. the demo function multicoredemo.m.

Discuss with other users here: http://groups.yahoo.com/group/multicore_for_matlab

I have spent many hours to develop this package. If you would like to let me know that you appreciate my work, you can do so by leaving a donation: https://www.paypal.com/cgi-bin/webscr?cmd=_s-xclick&hosted_button_id=GPUZTN4K63NRY

Keywords: Parallel processing, distributed computing, multiple cores.

• Required Products: MATLAB
• MATLAB release: MATLAB 7.5 (R2007b)

[David Trebing]

 

[Yulin]

I test this code and compared with parfor

Elapsed time running STARTMULTICOREMASTER: 4.80 seconds.
Elapsed time running STARTMULTICOREMASTER: 4.72 seconds.
Elapsed time running STARTMULTICOREMASTER: 4.70 seconds.
Elapsed time running STARTMULTICOREMASTER: 4.69 seconds.
Elapsed time running STARTMULTICOREMASTER: 4.70 seconds.
Elapsed time without slave support: 20.84 seconds.

and with parfor only
Elapsed time running TESTFUN with parfor only: 3.21 seconds.

it seems that parfor is more powerful and simple to use.

[Alan Mackay]

Very useful tool for running parallel sessions. With a few minor tweaks to code, primiarly additional 'set up' and 'clean up' functions to handle opening and closing minimalist slave sessions, I have run this across multiple cores on the same machine and across multiple machines too.

Currently running this quite happily with ~23/24 sessions.

[Alan Mackay]

 

[Tim]

Great, works exactly as described! It's a bit ridiculous that this functionality isn't included natively in Matlab considering how much we pay for the software.

[haidi]

Hi, has anyone been successful using this package for a larger scale. In my case, it actually does not work very well when running on 100 cores. For some reasons the slave got stuck in a loop with the message "Ignoring old semaphore of file"???

[haidi]

Great work!!
Is there a way to use this package without having to manually starting Matlab?
The reason I ask the question is as follows. I use Torque to submit to a cluster of 16 nodes, each node having 64 cores. However, I cannot start multiple matlab instances in a single node (even it has 64 cores). Your help is greatly appreciated!!! Many thanks.

[Pink_panther]

I activated only 3 slaves. Demo works great on my 8 core laptop! Be sure each session has path set to see the multicore folder.

>> multicoredemo
Elapsed time running STARTMULTICOREMASTER: 7.04 seconds.
Elapsed time running STARTMULTICOREMASTER: 7.39 seconds.
Elapsed time running STARTMULTICOREMASTER: 7.35 seconds.
Elapsed time running STARTMULTICOREMASTER: 6.74 seconds.
Elapsed time running STARTMULTICOREMASTER: 6.77 seconds.
Elapsed time without slave support: 20.86 seconds.
Elapsed time running TESTFUN directly: 19.84 seconds.

[Pink_panther]

 

[Pink_panther]

 

[Phil Corbishley]

Works very well, thanks

[Rohit Verma]

I tried running my function simultaneously with 3 different datasets together, but the slave processes doesnt do anything and the time is the same as if I am running without it.

[Rohit Verma]

Can I use it for running multiple processes accessing the same function using different parameter cell. Please note that the function takes in image input in each call. Will that be a problem ?

Thanks very nice code

[Zhanhong]

Great Package! Definitely useful for multicore CPUs. I have a 6 core AMD. It's such a pain if MATLAB can't run parallel.
I have a demo tip for newbies:
If you want to see the effect, make sure your function have to run at least several times on the input cell. If your function only has one input, all the slave sessions will be doing nothing because the function is already running on master. You'd probably want to make your input into segments to make all the slaves run simultaneously.

[laoya]

The tool is really powerful. I want to know if we can develop a similar tool by Fortran or C language. There are two reasons:
1) since every master and slave program need a matlab window, it is too expensive to buy multiple licenses of Matlab to run on different machines;
2) the slave program is launched by matlab, which will also need more than 100 MB memory, however, maybe the slave program only need to launch another external execute program with different parameters. Write a pure master/pure program will decrease the memory usage greatly.

Thanks,
Zhanhgong Tang

[Jason D]

 

[Christopher Carr]

 

[Christopher Carr]

 

[Christopher Carr]

 

[Giovanni Bracco]

Simply wonderful!
I have an optimization problem -including several launches of a Simulink model- running on a single core in a little more than 30 hours. By reformulating the problem as required by the Marcus' scripts (half a day work) I'm currently using five Windows PCs with a total of 14 cores and carrying out the simulation in 3.1 hours.
Thank you!!!

[Giovanni Bracco]

 

[Xinghua Lou]

Hi Markus,

Great work!

I may have one suggestion: the file I/O becomes a bottleneck in my application since saving the meta-data of a task (large image sequences) costs almost as much time as processing the task. Maybe it helps a lot if the file I/O can be replace by shared memory functions and there is a new Matlab library for use: http://www.mathworks.com/matlabcentral/fileexchange/28572-sharedmatrix. I think it is a perfect complement to your library.

Best,
Xinghua

[Darin McCoy]

nevermind my previous comment.....i didnt read the instructions :)

5 stars for the m file and 6 stars for customer service. Thanks Markus!

[Darin McCoy]

No improvement running the multicoredemo.m file

Elapsed time running STARTMULTICOREMASTER: 21.53 seconds.
Elapsed time running STARTMULTICOREMASTER: 21.67 seconds.
Elapsed time running STARTMULTICOREMASTER: 21.31 seconds.
Elapsed time running STARTMULTICOREMASTER: 21.31 seconds.
Elapsed time running STARTMULTICOREMASTER: 21.30 seconds.
Elapsed time without slave support: 21.14 seconds.
Elapsed time running TESTFUN directly: 20.00 seconds.

[Johnny Ta]

awesome. you're my savior. the code works like charm!

[Torfinn]

Thank you for these tools, they are vastly useful and will save me much time.

[Hamid Badi]

Great

[Hamid Badi]

 

[Robert Stead]

I'm having problems with the lasterror function in this code. There appear to be several instances where the lasterror function is passed a string 'reset' as an input argument, but the function lasterror is only defined for inputs of structure type. This causes errors at several points in the code, and I am unable to run the multicoredemo routine. I'm sure this is something I'm doing wrong, but I'd be grateful if someone could help me!

[Karl]

Hi Markus,

first of all -- you've developed a great tool that helps me a lot with my simulations in the field of audio signal processing. Seeing my dual quad core at 100% (instead of 13%) load warms my heart :).

Well, I'm not sure whether I'm getting something wrong here, but I had some problems when the function that is executed by the multicoremaster() (and the slaves) has more than one return value. It seems that in this case all but the first return values get lost. I applied a little trick that I found out about some time ago to solve this problem:
Everytime that feval() is called (in startmulticoremaster() and startmulticoreslave() ) I added something like this:

N_returnValues = nargout(functionHandleCell{k});
clear('returnValue'); % this is dirty! The next call doesn't work
% without clearing "returnValue" beforehand if
% N_returnValues==1. If it's greater->no
% problem (even without clearing
% "returnValue")
[returnValue{1:N_returnValues}] = feval(functionHandleCell{k}, parameterCell{k}{:}); % ha!
resultCell{k} = returnValue;

Doing so, the resultsCell that is returned from startmulticoremaster() is always a cell -- even if the called function has only one return value...

I hope this is of any value to anybody and that I'm not causing trouble by posting this hack :). I'm always open to learn a better solution....

Cheers, and thanks again for Multicore!

Karl

[Karl]

 

[DAdler]

Thank you very much for this great tool! I started using your code a few of months ago, and I must say it saved me lots of hours of work.

[Johannes Wunsch]

Awesome tool, I use it for fitting a computationally expensive financial model and it works just great. Thanks a lot for publishing it!! Johannes

[Amir]

I have little bit of problem running the master and slave processes over the network. I am not sure how to share the folder over a linux network!
Anybody can help?

[German]

sorry just missed to start a second matlab session with "startmulticoreslave".
Great code.

[German]

Hello, when i am running the multicoredemo, only the master is working, but not the slave. What am i doing wrong?
multithreading unabled/ is set to one core.
I use a duo core processor with windows vista and Matlab 7.8.0 R2009a 64-bit.
Thank you very much.

[Nir]

Great Work !
Speeds up my work more than twice on a quad computer. Not much change had to be done in order to use it.
Thanks
Nir

[Thomas]

Great tool!

[dpb10]

 

[Richard]

Brilliant tool! Great being able to sit back and watch a progress bar sliding along as a room full of computers gets to work doing your simulation.

I have a question though - what dimensions are typically used for parameterCell? I've tried doing some large multidimensional runs (e.g. 4x150x10) and things seemed to grind to a halt - I'm still looking into it, just wondered if the dimensions I'm using are typical or too large.

Cheers. Great work,
Richard.

[Richard Crozier]

Fantastic program, and particularly suited to my work with genetic algorithms. There is one mnor error I've noticed though. In startmulticoreslave, if you activate debug mode you reach the following line (77):

fileNr = str2double(regexptokens(parameterFileName,...
'parameters_\d+_(\d+)\.mat'));

But there is no regexptokens function, at least there isn't in R2007a or R2007b or R2008a. My solution is to replace this with the following lines (although I'm sure someone could come up with something more robust and/or elegent).

fileNrCell = regexp(parameterFileName,'parameters_\d+_(\d+)\.mat', 'tokens');

fileNr = str2double(fileNrCell{1});

The program is excellent though, thanks again!

[Markus Buehren]

I have opened a discussion group for the Multicore package on Yahoo. Please join and discuss with other users!

http://groups.yahoo.com/group/multicore_for_matlab/

[Moody]

I've been using multicore for a while now and its absolutely excellent. I'm running on 5 dual xeon x5460 as well as a couple of quad core boxes.

I was wondering if anyone compared performance of this toolbox with the parfor parallel computing matlab toolbox. Are they comparable?

I believe I'm bottlenecked now due to the hard disk I/O, so I was looking at the in memory possibilities of this or potentially upgrading my hd's to solid state to reduce the overhead.

BTW, I also tried precreating all the mat files once instead of doing multiple loops to reduce the I/O. Unfortunately, that didn't help as much as I hoped.

Don't get me wrong though, this is much, much, much faster than single threading, but as always we need to keep pushing :).

[Andrew Scott]

 

[Jordi Arnabat]

Thanks for this great contribution, it's very useful.

Correction:
I've used in under a grid of computers running different OS: GNU/Linux, Mac and Windows (XP). When the shared folder is on a network computer (not mapped to a local drive, for example: \\servername\sharedfolder); Windows systems fail trying to delete the semaphores, causing the master process run forever.

The solution I found is to slightly modify compsep.m and concatpath.m as follows:

_______________________________________________________
function str = chompsep(str)
unix_sep = '/';
pc_sep = '\';

if isunix && str(1)==pc_sep
str = strrep(str, pc_sep, unix_sep);
elseif ispc && str(1)==unix_sep
str = strrep(str, unix_sep, pc_sep);
end

if ~isempty(str) && (str(end) == unix_sep || str(end) == pc_sep)
str(end) = '';
end

_______________________________________________________
function str = concatpath(varargin)
unix_sep = '/';
pc_sep = '\';

str = '';
for n=1:nargin
curStr = varargin{n};
str = fullfile(str, chompsep(curStr));
end

if isunix && str(1)==pc_sep
str = strrep(str, pc_sep, unix_sep);
elseif ispc && str(1)==unix_sep
str = strrep(str, unix_sep, pc_sep);
end

[Vasilis Kapetanidis]

Thank you! This works just fine and now I have 100% CPU usage on all 4 cores! By measuring the elapsed time it seems that it runs about 3.4 times faster than with a single matlab doing all the work, so that's about 85% efficient on my quad-core

now, if only this could run on a single multi-core machine with only one matlab instance running

[Arturo Serrano]

 

[Arturo Serrano]

I got the same problem as Rohaly. When master ends the computation, and there is a slave still working, the master computes the remaining job again, yielding an extra iteration.
The solution is to set MAXMASTEREVALUATIONS, with all its drawbacks, since i understand that this isn't a bug rather than a problem not knowing if the slave got interrupted.

BTW, it works like a charm.

[Marcio Sales]

I tested the functions on two dual core machines. I had great gain when paralellizing processing between the processors of dual core machine or between the two machines using a single processor in each. However, I had no significant gain when trying to using both processors on both machines. Is that because the gain of using more processors is being reduced by increased load of data recording when you add more processors/machines? Also, there are times when I get an error in which one of the workers can't delete the temporary files and this seems to happen more frequently when you increase the number of workers. Is anyone having the same issues? My two machines run Vista 64bits.

[Janos Rohaly]

It seems there is the possibility for master and slave to simultaneously evaluate the same set of parameters. For example, if slave starts evaluating a slow process, master can catch up, and there is nothing to prevent it to start the very same computation since slave hasn't generated the result file yet. There is also a bug in setfilesemaphore.m. dirStruct(k).datenum in line 78 should be datenum(dirStruct(k).date).

[Bruno Cordani]

Great!!!

[M H]

Its absolutely excellent. Am using it now on my quad core machine and am probably going to buy another quad core just to see my models run so quickly. :)

[Robert Turner]

Brilliant library. Works like a charm

[uju jbl]

 

[Jun Kim]

This process works very well. For my model estimation, I was able to cut the execution time in a drastic manner. Also Markus was kind and was very responsive to my question.

[Markus Buehren]

> An option for avoiding the use of the
> master core is desirable

The option is already existing: You can use the input parameter MAXMASTEREVALUATIONS and set it to zero.

[Igor S]

An option for avoiding the use of the master core is desirable
Indeed if one slave process terminates or crushes the entiere process continues but if by chance the iteration that crushes is on the master core all the process is compromised

[igor scardanzan]

great , just some difficulties to kill the slave : the process persists and CNTR C does not work . one should await the execution end

[A. S.]

Thanks, very useful. Synchronization is not optimal (for example, the master shouldn't start working on a task if a slave is already working on it), but still a great program.

[Andrea Soldan]

very useful and it works excellently.
much more than the distribuited computing toolbox provided by Matlab (which is very hard to use).
my SO is Linux, and i'm working with 4 workers ( 2 dual-core processors)

[David Brown]

Works excellently. It would be nice to see this turned into a fully-guided setup to use this.

[Huy Bui]

Multicore works quite well overall. I got a bug though. I make a mistake in parameterCell. The slave processes all die because of that. When I tried to exit all slave processes & start again, the same error causing slave processes dead appears again & again.

[Kevin Thom]

Awesome program ... I have run it successfully using anywhere from 4 processors on one machine to 10 processors on 5 machines ... it makes a whole range of computationally expensive projects feasible in MATLAB.

[happy matlabuser]

Ran it with 8 processors across 6 machines, and it works beautifully. Unfortunately, if you kill one or more processors, the master processor MUST do that job. Since the jobs are long for my problem, it's better to kill everything in that situation and finish everything at the command line. The master starts at the top of the list, and the slaves start at the bottom. When they meet somewhere in the middle, the master will always redo one of the jobs. I don't think the code will be efficient for a very large number of very small jobs (correct me if I'm wrong); so, I recommend making jobs medium length, (total run time)/(10*(# of processors)) for example. For my problem, these are fairly minor concerns. The author did a great job with this code -- easily saving me hours of work -- thank you!

[Markus Buehren]

Yes and no: The slave process should create the directory if it is not existing (I have updated that). However, you can start the slave processes whenever you like! You can also interrupt and restart them while the master is running.

[Darren 3M]

Brilliant use of the filesystem to share the load. It's not quite 2x increase but on a quick cluster test I got an increase of 4x with 5CPU's so 80% efficient.

[schena gianni]

on dual-processor Intel Xeon based machines it halfs calculation time i.e. it cuts by a factor 2 !

[Michal Kvasnicka]

Wow!!! After the few hours of hard experimentation with MULTICORE I finally learned how to use this code for parallel running on my four core PC. This is realy good and useful tool for distributed computing!!!

1. Informational text in the demo must be extended to detailed description how to run "tesfun" in parallel regime.
2. Some work must be done to minimize interprocess communication overhead, which may be very itensive (25% of the overall load) in some cases.

Good work!!!

[Michal Kvasnicka]

I am not able to reproduce any improvment from sequential to parallel (multicore) realization of the testing demo code.

I would go as far as to say, that parallel (multi-core) realization is slower then sequential in some cases.

[William Renaud]

Would it be possible to make this compatible with Octave? Due to licensing restrictions it is difficult for many people to have numerous Matlab instances available.

[Zhijun Wang]

Corrections:

I tested the programn to see whether this program can improve parallel processing in a single machine with the following code:

______________________
N=20;
for m = 1:10
tic
for z = 1:N
testfun(z)
end
toc
end
__________________________

Results show the program do not improve anything comparing with my code in a single machine!

So I rate again

[Zhijun Wang]

Parallel processing on multiple cores in a single machine is very useful!

[lucia Come]

long due as standard matlab capability
does it work also with scrits or only with functions ?

[Michal Kvasnicka]

The demo should be more selfdescriptive. Comparison with single core demo running is very important for parallelization impact evaluation.