PoolClose

PoolClose closes the pool of MATLAB instances opened with PoolPrepare to execute code in parallel

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Syntax

  • tend=PoolClose(cleanpool, tstart, progbar, usePCT, usematlabpool)example

Description

PoolPrepare and PoolClose are used respectively to open and close a prespecified number of parallel MATLAB sessions, which need to be distributed over the physical cores where MATLAB is running.

example

tend =PoolClose(cleanpool, tstart, progbar, usePCT, usematlabpool) Sequential vs parallel run.

Examples

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  • Sequential vs parallel run.

    • n = 50000;
x = randn(1,n) ;
y = zeros(1,n);
% sequential run
tic
for i = 1 : n
y(i) = std(x(1:i));
end
fprintf('\n\n\n  Normal for: %f secs \n \n ',toc);
% parallel run
numpool = 4;
pariter = n;
UserOptions = {};
[numpool, tstart, progbar, usePCT, usematlabpool] = ...
PoolPrepare(numpool,pariter,UserOptions);
parfor i = 1 : n
y(i) = std(x(1:i));
end
cleanpool = 1; % this closes the pool of MATLAB sessions
tend = PoolClose(cleanpool, tstart, progbar, usePCT,  usematlabpool);
fprintf('\n\n\n      parFor: %f secs\n\n',tend);

    Input Arguments

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    cleanpool — Function name. Scalar {0,1}.

    Indicated if the open pool must be closed or not. It is useful to leave it open if there are subsequent parallel sessions to execute, so that to save the time required to open a new pool.

    Data Types: integer | logical

    tstart — Time stamp produced by PoolPrepare. Double.

    Contains the internal computer time at the end of the execution of the PoolPrepare function, so that to monitor the overall execution time of the statements embedded between PoolPrepare and PoolClose.

    Data Types: double

    progbar — Status of the progress bar generated by PoolPrepare. Structure or integer.

    Contains the status of the progress bar used to monitor the progression of the parallel execution.

    Data Types: struct | double Optional Input arguments:

    usePCT — Boolean indicating if the parallel computing toolbox is installed. Scalar {0,1}.

    Parpool checks for the existence of the parallel computing toolbox. 'usePCT' returns the result of the check to PoolClose, to avoid additional unnecessary checks.

    Data Types: integer | logical

    usematlabpool — Boolean indicating the use of 'usematlabpool' or 'parpool'. Scalar {0,1}.

    Boolean indicating if the pool of MATLAB instances is created using 'matlabpool' or 'parpool', depending on the MATLAB version installed. From R2013b 'parpool' is used. Earlier releases use 'usematlabpool'.

    Data Types: integer | logical

    Output Arguments

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    tend —Time execution of the parallel instances. Scalar

    Contains the execution time of the statements between PoolPrepare and PoolClose.

    Data Types - double

    References

    See Also

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