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vectorwise parallelization with pararrayfun

 From: dariodematties Subject: vectorwise parallelization with pararrayfun Date: Fri, 7 Jul 2017 08:31:35 -0700 (PDT)

Hello People,

Suppose I have a function called function1, which processes element-wise
computation on a vector of
dimensionality (1,n). Where n > 1. For example:

1 # This is a function to test parallel package
2 function        outputs = function1(inputs)
3         if ( rows(inputs) != 1 || columns(inputs) <= 1 )
4                 error("in function1: bad inputs array dimensionality");
5         endif
6         outputs = [];
7         for i = 1:columns(inputs)
8                 if ( i == 1 )
9                         outputs(1,i) = (log(inputs(1,i)) +
log(inputs(1,i+1)))/2;
10                 elseif ( i == columns(inputs) )
11                         outputs(1,i) =
outputs(1,i-1)*(log(inputs(1,i-1)) + log(inputs(1,i)))/2;
12                 else
13                         outputs(1,i) =
outputs(1,i-1)*(log(inputs(1,i-1)) + log(inputs(1,i)) +
log(inputs(1,i+1)))/3;
14                 endif
15         endfor
16 endfunction

In this function, the iterations must be executed sequentially in order to
keep the integrity of the computation.

Now, suppose I have a second function called function2, which is a kind of
wrapper that uses function1 to process an array of dimensionality (m,n)
-where m > 1- vector by vector (i,:). Let's say:

1 # This is a function to test parallel package
2 function        outputs = function2(inputs)
3         if ( rows(inputs) <= 1 || columns(inputs) <= 1 )
4                 error("in function2: bad inputs array dimensionality");
5         endif
6         outputs = [];
7         for i = 1:rows(inputs)
8                 outputs(i,:) = function1(inputs(i,:));
9         endfor
10 endfunction

My question is: How can I use pararrayfun to parallelize function2 in a way
that just function2 is concurrent but not function1?
That is to say: I want concurrency only among different rows of inputs
array, but I want no concurrency at all inside of function1.

Thanks

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