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parallel stream calculate matrix

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  parallel stream calculate matrix Philipp Kraus <philipp.kraus.flashpixx@gmail.com> - 2015-10-27 14:44 -0700

#32945 — parallel stream calculate matrix

Hello,

I would like to calculate row-wise a matrix with a parallel stream. In a short excerpt of my code:

Map<myData, Double> x = new HashMap();
ArrayList<myData> y = new ArrayList( x.keySet() );

Matrix m = new Matrix( y.size(), y.size() );

for( int i=0; i < y.size(); i++)
{
      for( int j= i+1; j < y.size(); j++)
      {
            double v = calculate( y.get(i), y.get(j) );
            m.set(i,j) = v;
            m.set(j,i) = v;
      }

      m.normalize(i);
}

I would like to do the first loop in parallel, because each row is independed from the others, but the first element on x must be defined on the first row / column on my matrix. My problem is, that I need on one hand an index value to address the cells within the matrix and the key value to calculate the value. I'm searching for a solution like zip in Python:

for index, data in zip()

(How) Can I do this in Java?

Thanks

Phil

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