docs: @Override
      public void solve(DMatrixRMaj B, DMatrixRMaj X) {
          if( B.numRows != numRows )
              throw new IllegalArgumentException("Unexpected dimensions for X: X rows = "+X.numRows+" expected = "+numCols);
          X.reshape(numCols,B.numCols);
  
          int BnumCols = B.numCols;
  
          Y.reshape(numRows,1, false);
          Z.reshape(numRows,1, false);
  
          // solve each column one by one
          for( int colB = 0; colB < BnumCols; colB++ ) {
  
              // make a copy of this column in the vector
              for( int i = 0; i < numRows; i++ ) {
                  Y.data[i] = B.get(i,colB);
              }
  
              // Solve Qa=b
              // a = Q'b
              CommonOps_DDRM.multTransA(Q,Y,Z);
  
              // solve for Rx = b using the standard upper triangular solver
              TriangularSolver_DDRM.solveU(R.data,Z.data,numCols);
  
              // save the results
              for( int i = 0; i < numCols; i++ ) {
                  X.set(i,colB,Z.data[i]);
              }
          }
      }