docs: public static DMatrixRMaj symmetricPosDef(int width, Random rand) {
          // This is not formally proven to work.  It just seems to work.
          DMatrixRMaj a = new DMatrixRMaj(width,1);
          DMatrixRMaj b = new DMatrixRMaj(width,width);
  
          for( int i = 0; i < width; i++ ) {
              a.set(i,0,rand.nextDouble());
          }
  
          CommonOps_DDRM.multTransB(a,a,b);
  
          for( int i = 0; i < width; i++ ) {
              b.add(i,i,1);
          }
  
          return b;
      }