NDpar package: Difference between revisions

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== Usage ==

To load the package, {{codeline|pkg load ndpar}}

=== setting CatDimensions and IdxDimensions - vectorized ===

Suppose we have a function that works along different dimensions of its input arguments, and returns arrays of different shapes like

<code>

<pre>

function [x, y] = f(u, v)

x = u + v.';

y = x.';

endfunction

</pre>

</code>

This function is used only to illustrate the syntax, not the usefulness of the extension.

Admittedly such a simple case could be handled easily either by changing the function or making a small wrapper to it. But it becomes really interesting when we are dealing with arrays of many and different dimensions (not shown here yet).

Applying this function to arrays u and v can be straightforwardly parallelized :

{{code|setting CatDimensions and IdxDimensions - vectorized|

<pre>

u = [1:10; 2:11];

v = u.';

[x, y] = ndpar_arrayfun(2, @f, u, v, "Vectorized", true, "ChunksPerProc", 2, "VerboseLevel", 1, "CatDimensions", [2 1],"IdxDimensions", [2 1] );

</pre>

}}

Here is the meaning of the options

* {{codeline|"IdxDimensions", [2 1]}} The parallelization (or slicing, or indexing) should be done along the 2nd dimension of {{codeline|u}} and 1st dimension of {{codeline|v}}. A value of 0 means no indexing (no slicing), so the argument would be passed "as is".

* {{codeline|"CatDimensions", [2 1]}} The outputs from each slice should be concatenated along the 2nd dimension of the first output and 1st dimension of the second output

* {{codeline|"Vectorized", true}} Use only if the function is vectorized along the "indexing" dimensions.

* {{codeline|"ChunksPerProc", 2}} It means that each process should make 2 chunks (2 calls to {{codeline|f}} with {{codeline|"Vectorized", true}}). Increase this number to minimize memory usage for instance. Increasing this number is also useful if function executions can have very different durations. If a process is finished, it can take over jobs from another process that is still busy.

NDpar package: Difference between revisions

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