docs: public static DMatrixRBlock initializeQ(DMatrixRBlock Q,
                                                int numRows , int numCols , int blockLength ,
                                                boolean compact) {
          int minLength = Math.min(numRows,numCols);
          if( compact ) {
              if( Q == null ) {
                  Q = new DMatrixRBlock(numRows,minLength,blockLength);
                  MatrixOps_DDRB.setIdentity(Q);
              } else {
                  if( Q.numRows != numRows || Q.numCols != minLength ) {
                      throw new IllegalArgumentException("Unexpected matrix dimension. Found "+Q.numRows+" "+Q.numCols);
                  } else {
                      MatrixOps_DDRB.setIdentity(Q);
                  }
              }
          } else {
              if( Q == null ) {
                  Q = new DMatrixRBlock(numRows,numRows,blockLength);
                  MatrixOps_DDRB.setIdentity(Q);
              } else {
                  if( Q.numRows != numRows || Q.numCols != numRows ) {
                      throw new IllegalArgumentException("Unexpected matrix dimension. Found "+Q.numRows+" "+Q.numCols);
                  } else {
                      MatrixOps_DDRB.setIdentity(Q);
                  }
              }
          }
          return Q;
      }