Method resize

src/util/sparse_matrix.h:65–67

    return value_.memSize() + index_.memSize() + offset_.memSize();
  }
  void resize(size_t rows, size_t cols, size_t nnz, bool row_major) {
    CHECK(false) << "TODO";
  }
 private:

  //// y = A * x, version 1. simper and faster