int n = I.numRows(), c = I.numColumns();
FlexCompRowMatrix Ac = new FlexCompRowMatrix(c, c);
double[] aiCol = new double[n];
double[] iCol = new double[n];
DenseVector aiV = new DenseVector(aiCol, false);
DenseVector iV = new DenseVector(iCol, false);
double[] itaiCol = new double[c];
DenseVector itaiV = new DenseVector(itaiCol, false);
int[] colptr = I.getColumnPointers();
int[] rowind = I.getRowIndices();
double[] Idata = I.getData();