parfor_progress.m

function percent = parfor_progress(N)
%PARFOR_PROGRESS Progress monitor (progress bar) that works with parfor.
%   PARFOR_PROGRESS works by creating a file called parfor_progress.txt in
%   your working directory, and then keeping track of the parfor loop's
%   progress within that file. This workaround is necessary because parfor
%   workers cannot communicate with one another so there is no simple way
%   to know which iterations have finished and which haven't.
%
%   PARFOR_PROGRESS(N) initializes the progress monitor for a set of N
%   upcoming calculations.
%
%   PARFOR_PROGRESS updates the progress inside your parfor loop and
%   displays an updated progress bar.
%
%   PARFOR_PROGRESS(0) deletes parfor_progress.txt and finalizes progress
%   bar.
%
%   To suppress output from any of these functions, just ask for a return
%   variable from the function calls, like PERCENT = PARFOR_PROGRESS which
%   returns the percentage of completion.
%
%   Example:
%
%      N = 100;
%      parfor_progress(N);
%      parfor i=1:N
%         pause(rand); % Replace with real code
%         parfor_progress;
%      end
%      parfor_progress(0);
%
%   See also PARFOR.

% By Jeremy Scheff - jdscheff@gmail.com - http://www.jeremyscheff.com/

if nargin < 1 
N = -1; 
end

percent = 0; 
w = 50; % Width of progress bar

if N > 0 
f = fopen(fullfile(tempdir,'parfor_progress.bin'), 'w'); 
if f<0 
error('Do you have write permissions for %s?', pwd); 
end 
fwrite(f,N,'uint32'); 
fwrite(f,0,'uint32'); 
fclose(f); 

if nargout == 0 
disp([' 0%[>', repmat(' ', 1, w), ']']); 
end 
elseif N == 0 
delete(fullfile(tempdir,'parfor_progress.bin')); 
percent = 100; 

if nargout == 0 
disp([repmat(char(8), 1, (w+9)), char(10), '100%[', repmat('=', 1, w+1), ']']); 
end 
else 
fname = fullfile(tempdir,'parfor_progress.bin'); 
if ~exist(fname, 'file') 
error('parfor_progress.bin not found. Run PARFOR_PROGRESS(N) before PARFOR_PROGRESS to initialize parfor_progress.bin.'); 
end

f = fopen(fname, 'r+'); 
A = fread(f,2,'uint32'); 
todo = A(1); 
progress = A(2) + 1; 
fseek(f, 4, 'bof'); 
fwrite(f,progress,'uint32'); 
fclose(f); 

percent = progress/todo * 100; 

if nargout == 0 
perc = sprintf('%3.0f%%', percent); % 4 characters wide, percentage 
disp([repmat(char(8), 1, (w+9)), char(10), perc, '[', repmat('=', 1, round(percent*w/100)), '>', repmat(' ', 1, w - round(percent*w/100)), ']']); 
end 
end