Mapper bug in version 0.5.2?

[rraymondhp]

When running this Grover-search tutorial to compile on ibmqx5,
https://github.com/rraymondhp/qiskit-tutorial/blob/ba1d80923fc02234f1fadda7be996bdd6fb4c712/reference/algorithms/grover_algorithm.ipynb

I encountered this error:

---------------------------------------------------------------------------
MapperError                               Traceback (most recent call last)
<ipython-input-9-3599bcf8da3e> in <module>()
     33 print(backend_coupling)
     34 
---> 35 compiled_circuit = qp.compile([circuitName], backend=backend, coupling_map=backend_coupling)
     36 compiled_qasm = qp.get_compiled_qasm(compiled_circuit, circuitName)
     37 print("Number of gates at ", circuitName, " circuit is ", len(compiled_qasm.split("\n")) - 4)

~/miniconda3/envs/QISKitenv/lib/python3.6/site-packages/qiskit/_quantumprogram.py in compile(self, name_of_circuits, backend, config, basis_gates, coupling_map, initial_layout, shots, max_credits, seed, qobj_id, hpc, skip_translation)
    990                                       config, basis_gates, coupling_map, initial_layout,
    991                                       shots, max_credits, seed, qobj_id, hpc,
--> 992                                       skip_translation)
    993         return qobj
    994 

~/miniconda3/envs/QISKitenv/lib/python3.6/site-packages/qiskit/wrapper/_wrapper.py in compile(circuits, backend, config, basis_gates, coupling_map, initial_layout, shots, max_credits, seed, qobj_id, hpc, skip_translation)
    167                                     config, basis_gates, coupling_map, initial_layout,
    168                                     shots, max_credits, seed, qobj_id, hpc,
--> 169                                     skip_translation)
    170 
    171 

~/miniconda3/envs/QISKitenv/lib/python3.6/site-packages/qiskit/_compiler.py in compile(circuits, backend, config, basis_gates, coupling_map, initial_layout, shots, max_credits, seed, qobj_id, hpc, skip_translation)
    148                 coupling_map=coupling_map,
    149                 initial_layout=initial_layout,
--> 150                 get_layout=True)
    151             # Map the layout to a format that can be json encoded
    152             list_layout = None

~/miniconda3/envs/QISKitenv/lib/python3.6/site-packages/qiskit/_compiler.py in compile_circuit(quantum_circuit, basis_gates, coupling_map, initial_layout, get_layout, format)
    228         logger.info("initial layout: %s", initial_layout)
    229         compiled_dag_circuit, final_layout = swap_mapper(
--> 230             compiled_dag_circuit, coupling, initial_layout, trials=20, seed=13)
    231         logger.info("final layout: %s", final_layout)
    232         # Expand swaps

~/miniconda3/envs/QISKitenv/lib/python3.6/site-packages/qiskit/mapper/_mapping.py in swap_mapper(circuit_graph, coupling_graph, initial_layout, basis, trials, seed)
    471             if k not in circ_qubits:
    472                 raise MapperError("initial_layout qubit %s[%d] not in input "
--> 473                                   "DAGCircuit" % (k[0], k[1]))
    474             if v not in coup_qubits:
    475                 raise MapperError("initial_layout qubit %s[%d] not in input "

MapperError: 'initial_layout qubit f_in[3] not in input DAGCircuit'

Expected Behavior

Should be no MapperError as the simulator (version 0.5.2) and all backends of version 0.4.15 can run without problem.

Current Behavior

See the error message above.

Possible Solution

Steps to Reproduce (for bugs)

Context

Your Environment

• Version used: qiskit 0.5.2
• Environment name and version (e.g. Python 3.6.1): Python 3.6.x
• Operating System and version: MacOSX

[nonhermitian]

Will look into it.

[nonhermitian]

See #494 for a fix.

[rraymondhp]

Thanks for the quick response!

[diego-plan9]

Fixed by #494