optimization for sparse tools (#4)
optimization for sparse tools (#4)

* optimization for sparse tools

* ix

* fix

kevinsung/OpenFermion,quantumlib/OpenFermion,jarrodmcc/OpenFermion,quantumlib/OpenFermion,quantumlib/OpenFermion,kevinsung/OpenFermion,jarrodmcc/OpenFermion,kevinsung/OpenFermion