setup_cluster_sharedmatrix.m

setup_cluster_sharedmatrix.m

% Start your pool!
% matlabpool open

%%
% this cell gets details about the pool to find a single worker on 
% each physical machine

% get all hosts and workers
spmd
    t = getCurrentWorker();
    ids = labindex;
    hosts = get(t,'Host');
    workers = get(t,'Name');
end

% convert from spmd objects
ids = {ids{:}};
hosts = {hosts{:}};
workers = {workers{:}};
uniquehosts = unique(hosts);
uniqueworkersidx = zeros(1,length(uniquehosts));

for hi=1:length(uniquehosts);
    % idx all workers on this host
    idx = cellfun(@(x) strcmpi(x, uniquehosts{hi}), hosts);
    % just take the first one
    uniqueworkersidx(hi) = min(find(idx));
end

% setup shared memory on each host 
% using only one worker per host
uniqueids = [ids{uniqueworkersidx}];

% uniqueids now contains the id of one worker per physical machine

%%
% set this a unique 5 digit key to identify the shared memory for your
% project
shmkey = 11112;
spmd
    % add path to all workers
    % this should be a shared drive or somewhere that all workers have access to
    % which contains the sharedmatrix package (if not already setup on each worker)
    % and your customised clonesharedmemory() function for loading your data set
    addpath('/analyse/pilots/robini/code')
    addpath('/analyse/pilots/robini/code/sharedmatrix')
    % only clone the shared memory on one worker per physical machine
    if ismember(labindex, uniqueids)
        % clonesharedmemory needs to be a function you write to load 
        % your data as appropriate
        % have to write it as a function to avoid having data in the spmd
        % scope which will be transmitted back to the client machine
        clonesharedmemory(shmkey)
        fprintf(1,'Id %i OK', labindex)
    end
end

%%
% now you can use your shared memory in all your workers
% things go a bit wonky if you don't detach and free properly
% so try to only attach to the big data at the start, extract the slice
% or data you need for that iteration and then detach ASAP
% Don't add the shared stuff until there are no other errors!
xavg = zeros(1,1000);
parfor i=1:1000
    x = sharedmatrix('attach', shmkey);
    xavg(i) = mean(x(i,:));
    sharedmatrix('detach', shmkey, x);
end


%%
% it might be a good idea to put a sharedmatrix option so you can run
% it with or without for testing... something like this (to give an idea
% - not tested)
%doshared = false;
%parfor i=1:1000
    %if doshared
        %x = sharedmatrix('attach',shmkey);
    %else
        %x = plain_data_load();
    %end
    %xavg(i) = mean(x(i,:));
    %if doshared
        %sharedmatrix('detach', shmkey, x);
    %end
%end

%%
% remember to free it at the end
% this will give an error if it is already freed 
spmd
    if ismember(labindex, uniqueids)
        sharedmatrix('free',shmkey);
    end
end

%%
% these frees on all workers just to be sure and catches any errors
spmd
    try sharedmatrix('free',shmkey);catch,end;
end