/in/foo.cc: In function 'int pcg(int, const std::vector<int>&, const std::vector<std::vector<int> >&, const Vec&, Vec&, ld, int)':
/in/foo.cc:32:8: warning: unused variable 'rr' [-Wunused-variable]
   32 |     ld rr = rho;
      |        ^~