parfor: error with feval

Question

Mahamed 2013-11-29

0
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https://ww2.mathworks.cn/matlabcentral/answers/108069-parfor-error-with-feval

评论： Walter Roberson 2018-12-22

Hi all,

I wrote a the following script, which uses parfor:

    N = 5;
    M = 10;
    x = rand(N,M);
    f = zeros(1,N);
    parfor j = 1:N
        f(j) = func(x(j,:), fun, opt_f);
    end

In "func", I call another function, "benchmark_func" where "feval" is used as follows:

f=feval(fhd,x)+f_bias(func_num);

I got the following error:

_Error using benchmark_func (line 76) Argument must contain a string or function_handle.

Error in func (line 22) fit = benchmark_func(x, fun);

Error in test_p (line 28) parfor j = 1:N

Caused by: Error using feval Argument must contain a string or function_handle._

I know we can't use "feval" inside parfor but is their a simple way to fix this.

Many thanks

Kind regards

Mahamed

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Mahamed 2013-11-30

编辑：Mahamed 2013-11-30

在 MATLAB Online 中打开

This is part of the benchmark_func code:

function f=benchmark_func(x,func_num)
global initial_flag
persistent fhd f_bias
if initial_flag==0
    if func_num==1 fhd=str2func('sphere_func'); %[-100,100]
    elseif func_num==2 fhd=str2func('schwefel_102'); %[-100,100]
  ...  
    elseif func_num==25 fhd=str2func('hybrid_rot_func4'); %[-5,5]  
    end
    load fbias_data;
end
f=feval(fhd,x)+f_bias(func_num);
function fit=sphere_func(x)
global initial_flag
persistent o M
[ps,D]=size(x);
if initial_flag==0
    load sphere_func_data
    if length(o)>=D
         o=o(1:D);
    else
         o=-100+200*rand(1,D);
    end
    initial_flag=1;
end
x=x-repmat(o,ps,1);
fit=sum(x.^2,2);
...
end

Edric Ellis 2013-12-2

在 MATLAB Online 中打开

You certainly can use FEVAL inside PARFOR - are you having trouble with that?

>> fh = {@sin, @cos, @tan};
>> parfor idx = 1:3, x(idx) = feval(fh{idx}, idx); end
>> x
x =
  0.8415   -0.4161   -0.1425

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Answer 1

Walter Roberson 2013-12-1

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https://ww2.mathworks.cn/matlabcentral/answers/108069-parfor-error-with-feval#answer_116845

在 MATLAB Online 中打开

I would suggest a table such as

funhandles = {@sphere_func, @schwefel_102, .... @hybrid_rot_func4};

then

fhd = funhandle{func_num};

and then

f = fhd(x) + f_bias(func_num);

Notice feval() is gone.

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Mahamed 2013-12-1

在 MATLAB Online 中打开

Many thanks for your valuable help. It is much appreciated.

I made the changes. The code is shown below. However, new error appears which is:

Error using benchmark_func (line 62) Subscript indices must either be real positive integers or logicals.

Error in func (line 22) fit = benchmark_func(x, fun);

Error in test_p (line 28) parfor j = 1:N

Caused by: Subscript indices must either be real positive integers or logicals.

function f=benchmark_func(x,func_num)
%global initial_flag
persistent fhd f_bias
initial_flag = 0;
if initial_flag==0
      funhandles = {@sphere_func, @schwefel_102, @high_cond_elliptic_rot_func, @schwefel_102_noise_func, ...
          @schwefel_206, @rosenbrock_func, @griewank_rot_func, @ackley_rot_func, @rastrigin_func, ...
          @weierstrass_rot, @schwefel_213, @EF8F2_func, @E_ScafferF6_func, @hybrid_func1, @hybrid_rot_func1, ...
          @hybrid_rot_func1_noise, @hybrid_rot_func2, @hybrid_rot_func2_narrow, @hybrid_rot_func2_onbound, ...
          @hybrid_rot_func3, @hybrid_rot_func3_highcond, @hybrid_rot_func3_noncont, @hybrid_rot_func4, ...
          @hybrid_rot_func4};
      fhd = funhandles(func_num);
      load fbias_data;
  end
f=fhd(x)+f_bias(func_num);

Mahamed 2013-12-2

在 MATLAB Online 中打开

Many thanks, Walter. You valuable help is much appreciated.

Sorry for the mistake. I did what you suggested but still get the following error: Error using benchmark_func (line 59) Subscript indices must either be real positive integers or logicals.

Error in func (line 22) fit = benchmark_func(x, fun);

Error in test_p (line 28) parfor j = 1:N

Caused by: Subscript indices must either be real positive integers or logicals.

The code is shown below:

if initial_flag==0
         funhandles = {@sphere_func, @schwefel_102, @high_cond_elliptic_rot_func, @schwefel_102_noise_func, ...
          @schwefel_206, @rosenbrock_func, @griewank_rot_func, @ackley_rot_func, @rastrigin_func, ...
          @weierstrass_rot, @schwefel_213, @EF8F2_func, @E_ScafferF6_func, @hybrid_func1, @hybrid_rot_func1, ...
          @hybrid_rot_func1_noise, @hybrid_rot_func2, @hybrid_rot_func2_narrow, @hybrid_rot_func2_onbound, ...
          @hybrid_rot_func3, @hybrid_rot_func3_highcond, @hybrid_rot_func3_noncont, @hybrid_rot_func4, ...
          @hybrid_rot_func4};
        fhd = funhandles{func_num};
      load fbias_data;
  end
f=fhd(x)+f_bias(func_num);

javeria barkat 2018-12-22

编辑：javeria barkat 2018-12-22

Mohamed kindly tell me how u have solved the problem of "Caused by: Subscript indices must either be real positive integers or logicals" as statd above ? I have the same problem.

I am using same benchmark_func.m file

Walter Roberson 2018-12-22

在 MATLAB Online 中打开

initial_flag = 0;
if initial_flag==0

should be

if isempty(initial_flag)

without initializing it to 0 every time.

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