/usr/share/octave/packages/parallel-2.2.0/parcellfun.m is in octave-parallel 2.2.0-1build1.
This file is owned by root:root, with mode 0o644.
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##
## This program is free software; you can redistribute it and/or modify it under
## the terms of the GNU General Public License as published by the Free Software
## Foundation; either version 3 of the License, or (at your option) any later
## version.
##
## This program is distributed in the hope that it will be useful, but WITHOUT
## ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
## FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
## details.
##
## You should have received a copy of the GNU General Public License along with
## this program; if not, see <http://www.gnu.org/licenses/>.
## -*- texinfo -*-
## @deftypefn{Function File} {[@var{o1}, @var{o2}, @dots{}] =} parcellfun (@var{nproc}, @var{fun}, @var{a1}, @var{a2}, @dots{})
## @deftypefnx{Function File} {} parcellfun (nproc, fun, @dots{}, "UniformOutput", @var{val})
## @deftypefnx{Function File} {} parcellfun (nproc, fun, @dots{}, "ErrorHandler", @var{errfunc})
## @deftypefnx{Function File} {} parcellfun (nproc, fun, @dots{}, "VerboseLevel", @var{val})
## @deftypefnx{Function File} {} parcellfun (nproc, fun, @dots{}, "ChunksPerProc", @var{val})
## Evaluates a function for multiple argument sets using multiple processes.
## @var{nproc} should specify the number of processes. A maximum recommended value is
## equal to number of CPUs on your machine or one less.
## @var{fun} is a function handle pointing to the requested evaluating function.
## @var{a1}, @var{a2} etc. should be cell arrays of equal size.
## @var{o1}, @var{o2} etc. will be set to corresponding output arguments.
##
## The UniformOutput and ErrorHandler options are supported with meaning identical
## to @dfn{cellfun}.
## A VerboseLevel option controlling the level output is supported.
## A value of 0 is quiet, 1 is normal, and 2 or more enables
## debugging output.
## The ChunksPerProc option control the number of chunks which contains elementary jobs. This
## option particularly useful when time execution of function is small. Setting this option
## to 100 is a good choice in most cases.
##
## Notice that jobs are served from a single first-come first-served queue,
## so the number of jobs executed by each process is generally unpredictable.
## This means, for example, that when using this function to perform Monte-Carlo
## simulations one cannot expect results to be exactly reproducible. The pseudo
## random number generators of each process are initialised with a unique state.
## This currently works only for new style generators.
##
## NOTE: this function is implemented using "fork" and a number of pipes for IPC.
## Suitable for systems with an efficient "fork" implementation (such as GNU/Linux),
## on other systems (Windows) it should be used with caution.
## Also, if you use a multithreaded BLAS, it may be wise to turn off multi-threading
## when using this function.
##
## CAUTION: This function should be regarded as experimental. Although all subprocesses
## should be cleared in theory, there is always a danger of a subprocess hanging up,
## especially if unhandled errors occur. Under GNU and compatible systems, the following
## shell command may be used to display orphaned Octave processes:
## ps --ppid 1 | grep octave
##
## @end deftypefn
## Author: Jaroslav Hajek <highegg@gmail.com>
## Several improvements thanks to: Travis Collier <travcollier@gmail.com>
function varargout = parcellfun (nproc, fun, varargin)
## The list of functions to be seeded in each slave.
persistent random_func_list = {@rand, @randn, @rande, @randp, @randg};
if (nargin < 3 || ! isscalar (nproc) || nproc <= 0)
print_usage ();
endif
if (ischar (fun))
fun = str2func (fun);
elseif (! isa (fun, "function_handle"))
error ("parcellfun: fun must be either a function handle or name")
endif
[nargs, uniform_output, error_handler, ...
verbose_level, chunks_per_proc] = parcellfun_opts (varargin);
args = varargin(1:nargs);
if (! all (cellfun ("isclass", args, "cell")))
error ("parcellfun: all non-option arguments except the first one must be cell arrays");
endif
if (nargs == 0)
print_usage ();
elseif (nargs > 1)
[err, args{:}] = common_size (args{:});
if (err)
error ("parcellfun: arguments size must match");
endif
endif
njobs = numel (args{1});
if (chunks_per_proc > 0 && chunks_per_proc < njobs / nproc)
## We need chunked evaluation.
## Function executed for a chunk.
if (isempty (error_handler))
chunk_fun = @(varargin) cellfun (fun, varargin{:}, "UniformOutput", uniform_output);
else
chunk_fun = @(varargin) cellfun (fun, varargin{:}, ...
"UniformOutput", uniform_output, "ErrorHandler", error_handler);
endif
[varargout{1:nargout}] = chunk_parcellfun (nproc, chunks_per_proc, ...
chunk_fun, [], verbose_level, args{:});
return
endif
nproc = min (nproc, numel (args{1}));
## create communication pipes.
cmdr = cmdw = resr = resw = zeros (nproc, 1);
err = 0;
for i = 1:nproc
## command pipes
[cmdr(i), cmdw(i), err, msg] = pipe ();
if (err)
break;
endif
## result pipes
[resr(i), resw(i), err, msg] = pipe ();
if (err)
break;
endif
endfor
if (! err)
## status pipe
[statr, statw, err, msg] = pipe ();
endif
if (err)
error ("failed to open pipe: %s", msg);
endif
iproc = 0; # the parent process
nsuc = 0; # number of processes succesfully forked.
fflush (stdout); # prevent subprocesses from inheriting buffered output
## get a seed and change state
seed = rand;
pids = zeros (nproc, 1);
## fork subprocesses
for i = 1:nproc
[pid, msg] = fork ();
if (pid > 0)
## parent process. fork succeded.
nsuc ++;
pids(i) = pid;
if (verbose_level > 1)
fprintf (stderr,'parcellfun: child process %d created\n', pids(i));
fflush (stderr);
endif
elseif (pid == 0)
## child process.
iproc = i;
break;
elseif (pid < 0)
## parent process. fork failed.
err = 1;
break;
endif
endfor
if (iproc)
## child process. close unnecessary pipe ends.
fclose (statr);
for i = 1:nproc
## we won't write commands and read results
fclose (cmdw (i));
fclose (resr (i));
if (i != iproc)
## close also those pipes that don't belong to us.
fclose (cmdr (i));
fclose (resw (i));
endif
endfor
else
## parent process. close unnecessary pipe ends.
fclose (statw);
for i = 1:nproc
## we won't read commands and write results
fclose (cmdr (i));
fclose (resw (i));
endfor
if (nsuc)
## we forked some processes. if this is less than we opted for, gripe
## but continue.
if (nsuc < nproc)
warning ("parcellfun: only %d out of %d processes forked", nsuc, nproc);
nproc = nsuc;
endif
else
## this is bad.
error ("parcellfun: failed to fork processes");
endif
endif
## At this point, everything should be OK (?)
if (iproc)
## the border patrol. we really don't want errors escape after the forks.
unwind_protect
try
## re-seed random number states, adjusted for each process
seed *= iproc*bitmax;
## FIXME: use cellfun when 3.4. is a requirement
for rf = random_func_list
feval (rf{1}, "state", seed);
endfor
## child process. indicate ready state.
fwrite (statw, -iproc, "double");
fflush (statw);
do
## get command
cmd = fread (cmdr(iproc), 1, "double");
if (cmd)
## we've got a job to do. prepare argument and return lists.
res = cell (1, nargout);
argsc = cell (1, nargs);
for i = 1:nargs
argsc{i} = args{i}{cmd};
endfor
if (isempty (error_handler))
## unguarded evaluation.
[res{:}] = fun (argsc{:});
else
## guarded evaluation
try
[res{:}] = fun (argsc{:});
catch
errs.index = cmd;
[errs.message, errs.identifier] = lasterr ();
[res{:}] = error_handler (errs, argsc{:});
end_try_catch
endif
## indicate ready state.
fwrite (statw, iproc, "double");
fflush (statw);
## write the result.
## FIXME: this can fail.
fsave (resw(iproc), res);
fflush (resw(iproc));
endif
until (cmd == 0)
catch
## just indicate the error. don't quit this function !!!!
fputs (stderr, "\n");
warning ("parcellfun: unhandled error in subprocess %d", iproc);
## send a termination notice.
fwrite (statw, -iproc, "double");
fflush (statw);
end_try_catch
unwind_protect_cleanup
## This is enclosed in another handler to prevent errors from escaping.
## If something goes wrong, we'll get a broken pipe signal, but anything
## is better than skipping the following __exit__.
try
fclose (statw);
fclose (resw(iproc));
fclose (cmdr(iproc));
end_try_catch
## no more work for us. We call __exit__, which bypasses termination sequences.
__exit__ ();
## we should never get here.
exit ();
end_unwind_protect
else
## parent process.
res = cell (nargout, njobs);
pjobs = 0;
pending = zeros (1, nproc);
unwind_protect
while (pjobs < njobs || any (pending))
## if pipe contains no more data, that's bad
if (feof (statr))
warning ("parcellfun: premature exit due to closed pipe");
break;
endif
## wait for a process state.
isubp = fread (statr, 1, "double");
if (isubp > 0)
ijob = pending(isubp);
## we have a result ready.
res(:, ijob) = fload (resr(isubp));
## clear pending state
pending(isubp) = 0;
else
isubp = -isubp;
if (pending(isubp))
## premature exit means an unhandled error occured in a subprocess.
## the process should have griped, we just try to exit gracefully.
pending(isubp) = 0;
## no more jobs to start.
njobs = pjobs;
## skip the rest; don't send commands to the process.
fclose(cmdw(isubp));
continue;
endif
endif
if (pjobs < njobs)
ijob = ++pjobs;
## send the next job to the process.
fwrite (cmdw(isubp), ijob, "double");
fflush (cmdw(isubp));
## set pending state
pending(isubp) = ijob;
else
## send terminating signal
fwrite (cmdw(isubp), 0, "double");
fclose (cmdw(isubp));
endif
if (verbose_level > 0)
fprintf (stderr, "\rparcellfun: %d/%d jobs done", pjobs - sum (pending != 0), njobs);
fflush (stderr);
endif
endwhile
if (verbose_level > 0)
fputs (stderr, "\n");
fflush (stderr);
endif
unwind_protect_cleanup
## send termination signals to active processes.
for isubp = find (pending)
## send terminating signal
fwrite (cmdw(isubp), 0, "double");
fclose (cmdw(isubp));
endfor
## explicitly recognize all terminated processes.
for i = 1:nproc
if (verbose_level > 1)
fprintf(stderr,'parcellfun: waiting for child process %d to close\n', pids(i));
fflush (stderr);
endif
[pid, status] = waitpid (pids(i));
endfor
## FIXME: I think order is possibly important here, and this is correct.
## close all pipe ends
fclose (statr);
for i = 1:nproc
fclose (resr(i));
endfor
end_unwind_protect
## we're finished. transform the result.
varargout = cell (1, nargout);
shape = size (varargin{1});
for i = 1:nargout
varargout{i} = reshape (res(i,:), shape);
if (uniform_output)
varargout{i} = cell2mat (varargout{i});
endif
endfor
endif
endfunction
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