code: @Override
      public boolean decompose( DMatrixRMaj mat ) {
          if( mat.numRows > maxWidth ) {
              setExpectedMaxSize(mat.numRows,mat.numCols);
          } else if( mat.numRows != mat.numCols ) {
              throw new IllegalArgumentException("Must be a square matrix.");
          }
  
          n = mat.numRows;
  
          T = mat;
          t = T.data;
  
          if(lower) {
              return decomposeLower();
          } else {
              return decomposeUpper();
          }
      }
docs: <p>
  Performs Choleksy decomposition on the provided matrix.
  </p>
  
  <p>
  If the matrix is not positive definite then this function will return
  false since it can't complete its computations.  Not all errors will be
  found.  This is an efficient way to check for positive definiteness.
  </p>
  @param mat A symmetric positive definite matrix with n &le; widthMax.
  @return True if it was able to finish the decomposition.