MatrixInfo info = r.readMatrixInfo();
if (info.isComplex()) throw new IllegalArgumentException("complex matrices not supported");
if (!info.isCoordinate()) throw new IllegalArgumentException("only coordinate matrices supported");
MatrixSize size = r.readMatrixSize(info);
numRows = size.numRows();
numColumns = size.numColumns();
links = new Linked();
int nz = size.numEntries();
int[] row = new int[nz];
int[] column = new int[nz];