The linear operator implementation for unrestricted UCCSD uses FermionOperator, which has poor performance. We should use a faster one that directly contracts the amplitudes tensor with the state vector, as is done for the restricted UCCSD implementation using pyscf.fci.direct_nosym.contract_2e (see here). This should be addressed via pyscf/pyscf#3125.
The linear operator implementation for unrestricted UCCSD uses FermionOperator, which has poor performance. We should use a faster one that directly contracts the amplitudes tensor with the state vector, as is done for the restricted UCCSD implementation using
pyscf.fci.direct_nosym.contract_2e(see here). This should be addressed via pyscf/pyscf#3125.