Free projection discrete propagator is incomplete

[bkesk]

Free projection is not fully implemented for model Hamiltonians which also directly prevent release-constraint calculations.

what I did

I attempted to run a release-constraint calculation using this input file:

{
  "afqmc": {
    "project": {
      "id": "qmc",
      "series": 0,
      "mixed_precision": false
    },
   "walker_set": {
       "name" : "my_walkers",
       "walker_type": "COLLINEAR"
    },
    "execute": {
      "walker_set": "my_walkers",
      "wavefunction": {
        "filename": "afqmc.h5"
      },
      "timestep": 0.01,
      "steps": 1000,
      "n_walkers_per_mpi_task": 400,
      "estimator": {
        "name": "energy",
        "overwrite": true,
        "print_components": true
      },
      "accumlate_interval": 10,
      "population_control_interval": 5,
      "walker_ortho_interval": 10,
      "measure_interval": 20
    },
    "execute": {
      "walker_set": "my_walkers",
	"propagator" : {
	    "free_projection": true,
	    "importance_sampling": false,
	    "apply_constrain": false
      },
      "wavefunction": {
        "filename": "afqmc.h5"
      },
      "timestep": 0.001,
      "steps": 10000,
      "n_walkers_per_mpi_task": 400,
      "estimator": {
        "name": "energy",
        "overwrite": true,
        "print_components": true
      },
      "accumlate_interval": 2,
      "population_control_interval": 2,
      "walker_ortho_interval": 2,
      "measure_interval": 50
    }
  }
}

Expected Behavior:

Running afqmc with this output should project with constrained path AFQMC (CP-AFQMC), then switch to a free-projection calculation after the CP-AFQMC finishes using the same walker set.

What actually happens

An error message is raised that says that the FP discrete propagator is not complete yet

[error] **********************************************
[error]         APPLICATION ABORT: Fatal Error.
[error] **********************************************
[error] Finish FP DiscretePropagator
[error] **********************************************