CODEWITHSUNDEEP
parallel-processingvectorization
MrDuk
MrDuk

Reputation: 18242

Can someone help me understand vectorization?

I'm really trying to wrap my head around vectorization but I can't seem to understand it. I don't know if I don't understand how to vectorize, or if I don't understand the array notation that's being used. An example of a loop I'm working on with school is below:

for (M=0; M< number_of_iterations/2; M++){
   for (i=2; i<n-1; i++)  
      for (j=1; j<n-1; j++)  
          y[i][j]= (x[i-1][j]+x[i][j-1]+x[i+1][j]+x[i][j+1]+x[i-2][j])/5.;

I'm not sure I quite understand the whole thing on dependencies - Is there a way to vectorize this using array notation as is, or do I need to adjust it somehow to account for dependencies throughout?

Thanks in advance for any help.

Upvotes: 0

Views: 36

Answers (2)

efsandino
efsandino

Reputation: 975

First I recommendo you to use brakets {} to organize your lines of code and understand it better. Second, take a look to this page: http://www.javatutorialhub.com/java-arrays.html Thirg, always start with easy examples to not get confused.

Upvotes: 1

David Schwartz
David Schwartz

Reputation: 182761

Assuming x and y are distinct arrays that don't overlap at all, there are no dependencies. x never changes, and all computations have results that only depend on x. No computation depends on the results of a prior computation.

The calculations and assignments used in that loop could occur in any order and with any concurrency.

Upvotes: 1

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